make the blkcg and blkcg structures private

make the blkcg and blkcg structures private

[Christoph Hellwig]

Hi all,

this series cleans up various lose end in the blk-cgroup code to make it
easier to follow in preparation of reworking the blkcg assignment for
bios.  The biggest change is that most of <linux/blk-cgroup.h> is now
taken private into block/.

Diffstat:
 block/Makefile                |    1 
 block/bfq-iosched.h           |    4 
 block/blk-cgroup-fc-appid.c   |   57 +++++++++
 block/blk-cgroup.c            |  154 ++++++++++++++++++++-----
 block/blk-cgroup.h            |  138 +++++++++++++++-------
 block/blk-throttle.c          |    2 
 drivers/block/loop.c          |   12 +
 drivers/nvme/host/fc.c        |   26 +---
 drivers/scsi/lpfc/lpfc_scsi.c |    4 
 include/linux/backing-dev.h   |    6 
 include/linux/blk-cgroup.h    |  258 ++----------------------------------------
 include/linux/blktrace_api.h  |   10 -
 include/linux/kthread.h       |    4 
 kernel/kthread.c              |    1 
 kernel/trace/blktrace.c       |   26 ++--
 mm/backing-dev.c              |   19 +--
 mm/readahead.c                |    1 
 mm/swapfile.c                 |    1 
 18 files changed, 343 insertions(+), 381 deletions(-)

[PATCH 01/15] blk-cgroup: remove __bio_blkcg

[Christoph Hellwig]

Remove the unused and deprecated __bio_blkcg helper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.h | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 47e1e38390c96..49e88fc9cc391 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -139,27 +139,6 @@ static inline struct cgroup_subsys_state *blkcg_css(void)
 	return task_css(current, io_cgrp_id);
 }
 
-/**
- * __bio_blkcg - internal, inconsistent version to get blkcg
- *
- * DO NOT USE.
- * This function is inconsistent and consequently is dangerous to use.  The
- * first part of the function returns a blkcg where a reference is owned by the
- * bio.  This means it does not need to be rcu protected as it cannot go away
- * with the bio owning a reference to it.  However, the latter potentially gets
- * it from task_css().  This can race against task migration and the cgroup
- * dying.  It is also semantically different as it must be called rcu protected
- * and is susceptible to failure when trying to get a reference to it.
- * Therefore, it is not ok to assume that *_get() will always succeed on the
- * blkcg returned here.
- */
-static inline struct blkcg *__bio_blkcg(struct bio *bio)
-{
-	if (bio && bio->bi_blkg)
-		return bio->bi_blkg->blkcg;
-	return css_to_blkcg(blkcg_css());
-}
-
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
  * @return: true if this bio needs to be submitted with the root blkg context.
@@ -471,8 +450,6 @@ static inline int blkcg_activate_policy(struct request_queue *q,
 static inline void blkcg_deactivate_policy(struct request_queue *q,
 					   const struct blkcg_policy *pol) { }
 
-static inline struct blkcg *__bio_blkcg(struct bio *bio) { return NULL; }
-
 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 						  struct blkcg_policy *pol) { return NULL; }
 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
-- 
2.30.2

[PATCH 01/15] blk-cgroup: remove __bio_blkcg

[Christoph Hellwig]

Remove the unused and deprecated __bio_blkcg helper.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 block/blk-cgroup.h | 23 -----------------------
 1 file changed, 23 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 47e1e38390c96..49e88fc9cc391 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -139,27 +139,6 @@ static inline struct cgroup_subsys_state *blkcg_css(void)
 	return task_css(current, io_cgrp_id);
 }
 
-/**
- * __bio_blkcg - internal, inconsistent version to get blkcg
- *
- * DO NOT USE.
- * This function is inconsistent and consequently is dangerous to use.  The
- * first part of the function returns a blkcg where a reference is owned by the
- * bio.  This means it does not need to be rcu protected as it cannot go away
- * with the bio owning a reference to it.  However, the latter potentially gets
- * it from task_css().  This can race against task migration and the cgroup
- * dying.  It is also semantically different as it must be called rcu protected
- * and is susceptible to failure when trying to get a reference to it.
- * Therefore, it is not ok to assume that *_get() will always succeed on the
- * blkcg returned here.
- */
-static inline struct blkcg *__bio_blkcg(struct bio *bio)
-{
-	if (bio && bio->bi_blkg)
-		return bio->bi_blkg->blkcg;
-	return css_to_blkcg(blkcg_css());
-}
-
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
  * @return: true if this bio needs to be submitted with the root blkg context.
@@ -471,8 +450,6 @@ static inline int blkcg_activate_policy(struct request_queue *q,
 static inline void blkcg_deactivate_policy(struct request_queue *q,
 					   const struct blkcg_policy *pol) { }
 
-static inline struct blkcg *__bio_blkcg(struct bio *bio) { return NULL; }
-
 static inline struct blkg_policy_data *blkg_to_pd(struct blkcg_gq *blkg,
 						  struct blkcg_policy *pol) { return NULL; }
 static inline struct blkcg_gq *pd_to_blkg(struct blkg_policy_data *pd) { return NULL; }
-- 
2.30.2

Re: [PATCH 01/15] blk-cgroup: remove __bio_blkcg

[Tejun Heo]

On Wed, Apr 20, 2022 at 06:27:09AM +0200, Christoph Hellwig wrote:
> Remove the unused and deprecated __bio_blkcg helper.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

[PATCH 02/15] nvme-fc: don't support the appid attribute without CONFIG_BLK_CGROUP_FC_APPID

[Christoph Hellwig]

nvme-fc appid support needs CONFIG_BLK_CGROUP_FC_APPID to work, so disable
the whole code if the option is not set.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/host/fc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 080f85f4105f3..caa0fff7bf1f5 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3831,6 +3831,9 @@ static ssize_t nvme_fc_nvme_discovery_store(struct device *dev,
 	return count;
 }
 
+static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
+
+#ifdef CONFIG_BLK_CGROUP_FC_APPID
 /* Parse the cgroup id from a buf and return the length of cgrpid */
 static int fc_parse_cgrpid(const char *buf, u64 *id)
 {
@@ -3898,12 +3901,14 @@ static ssize_t fc_appid_store(struct device *dev,
 		return -EINVAL;
 	return count;
 }
-static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
 static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
+#endif /* CONFIG_BLK_CGROUP_FC_APPID */
 
 static struct attribute *nvme_fc_attrs[] = {
 	&dev_attr_nvme_discovery.attr,
+#ifdef CONFIG_BLK_CGROUP_FC_APPID
 	&dev_attr_appid_store.attr,
+#endif
 	NULL
 };
 
-- 
2.30.2

[PATCH 02/15] nvme-fc: don't support the appid attribute without CONFIG_BLK_CGROUP_FC_APPID

[Christoph Hellwig]

nvme-fc appid support needs CONFIG_BLK_CGROUP_FC_APPID to work, so disable
the whole code if the option is not set.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 drivers/nvme/host/fc.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index 080f85f4105f3..caa0fff7bf1f5 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3831,6 +3831,9 @@ static ssize_t nvme_fc_nvme_discovery_store(struct device *dev,
 	return count;
 }
 
+static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
+
+#ifdef CONFIG_BLK_CGROUP_FC_APPID
 /* Parse the cgroup id from a buf and return the length of cgrpid */
 static int fc_parse_cgrpid(const char *buf, u64 *id)
 {
@@ -3898,12 +3901,14 @@ static ssize_t fc_appid_store(struct device *dev,
 		return -EINVAL;
 	return count;
 }
-static DEVICE_ATTR(nvme_discovery, 0200, NULL, nvme_fc_nvme_discovery_store);
 static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
+#endif /* CONFIG_BLK_CGROUP_FC_APPID */
 
 static struct attribute *nvme_fc_attrs[] = {
 	&dev_attr_nvme_discovery.attr,
+#ifdef CONFIG_BLK_CGROUP_FC_APPID
 	&dev_attr_appid_store.attr,
+#endif
 	NULL
 };
 
-- 
2.30.2

[PATCH 03/15] nvme-fc: fold t fc_update_appid into fc_appid_store

[Christoph Hellwig]

No need for this wrapper.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/nvme/host/fc.c | 19 +++----------------
 1 file changed, 3 insertions(+), 16 deletions(-)

diff --git a/drivers/nvme/host/fc.c b/drivers/nvme/host/fc.c
index caa0fff7bf1f5..7ae72c7a211b9 100644
--- a/drivers/nvme/host/fc.c
+++ b/drivers/nvme/host/fc.c
@@ -3857,12 +3857,10 @@ static int fc_parse_cgrpid(const char *buf, u64 *id)
 }
 
 /*
- * fc_update_appid: Parse and update the appid in the blkcg associated with
- * cgroupid.
- * @buf: buf contains both cgrpid and appid info
- * @count: size of the buffer
+ * Parse and update the appid in the blkcg associated with the cgroupid.
  */
-static int fc_update_appid(const char *buf, size_t count)
+static ssize_t fc_appid_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
 {
 	u64 cgrp_id;
 	int appid_len = 0;
@@ -3890,17 +3888,6 @@ static int fc_update_appid(const char *buf, size_t count)
 		return ret;
 	return count;
 }
-
-static ssize_t fc_appid_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t count)
-{
-	int ret  = 0;
-
-	ret = fc_update_appid(buf, count);
-	if (ret < 0)
-		return -EINVAL;
-	return count;
-}
 static DEVICE_ATTR(appid_store, 0200, NULL, fc_appid_store);
 #endif /* CONFIG_BLK_CGROUP_FC_APPID */
 
-- 
2.30.2

[PATCH 04/15] blk-cgroup: move blkcg_{get,set}_fc_appid out of line

[Christoph Hellwig]

No need to have these helpers inline.  Also remove the stubs and just use
an IS_ENABLED for the get side (the set side already is only built
conditionlly).

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/Makefile                |  1 +
 block/blk-cgroup-fc-appid.c   | 57 ++++++++++++++++++++++++++++++++++
 drivers/scsi/lpfc/lpfc_scsi.c |  4 ++-
 include/linux/blk-cgroup.h    | 58 ++---------------------------------
 4 files changed, 63 insertions(+), 57 deletions(-)
 create mode 100644 block/blk-cgroup-fc-appid.c

diff --git a/block/Makefile b/block/Makefile
index 3950ecbc5c263..4e01bb71ad6e0 100644
--- a/block/Makefile
+++ b/block/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_BLK_DEV_BSG_COMMON) += bsg.o
 obj-$(CONFIG_BLK_DEV_BSGLIB)	+= bsg-lib.o
 obj-$(CONFIG_BLK_CGROUP)	+= blk-cgroup.o
 obj-$(CONFIG_BLK_CGROUP_RWSTAT)	+= blk-cgroup-rwstat.o
+obj-$(CONFIG_BLK_CGROUP_FC_APPID) += blk-cgroup-fc-appid.o
 obj-$(CONFIG_BLK_DEV_THROTTLING)	+= blk-throttle.o
 obj-$(CONFIG_BLK_CGROUP_IOPRIO)	+= blk-ioprio.o
 obj-$(CONFIG_BLK_CGROUP_IOLATENCY)	+= blk-iolatency.o
diff --git a/block/blk-cgroup-fc-appid.c b/block/blk-cgroup-fc-appid.c
new file mode 100644
index 0000000000000..760a2e1878dde
--- /dev/null
+++ b/block/blk-cgroup-fc-appid.c
@@ -0,0 +1,57 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "blk-cgroup.h"
+
+/**
+ * blkcg_set_fc_appid - set the fc_app_id field associted to blkcg
+ * @app_id: application identifier
+ * @cgrp_id: cgroup id
+ * @app_id_len: size of application identifier
+ */
+int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len)
+{
+	struct cgroup *cgrp;
+	struct cgroup_subsys_state *css;
+	struct blkcg *blkcg;
+	int ret  = 0;
+
+	if (app_id_len > FC_APPID_LEN)
+		return -EINVAL;
+
+	cgrp = cgroup_get_from_id(cgrp_id);
+	if (!cgrp)
+		return -ENOENT;
+	css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);
+	if (!css) {
+		ret = -ENOENT;
+		goto out_cgrp_put;
+	}
+	blkcg = css_to_blkcg(css);
+	/*
+	 * There is a slight race condition on setting the appid.
+	 * Worst case an I/O may not find the right id.
+	 * This is no different from the I/O we let pass while obtaining
+	 * the vmid from the fabric.
+	 * Adding the overhead of a lock is not necessary.
+	 */
+	strlcpy(blkcg->fc_app_id, app_id, app_id_len);
+	css_put(css);
+out_cgrp_put:
+	cgroup_put(cgrp);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(blkcg_set_fc_appid);
+
+/**
+ * blkcg_get_fc_appid - get the fc app identifier associated with a bio
+ * @bio: target bio
+ *
+ * On success return the fc_app_id, on failure return NULL
+ */
+char *blkcg_get_fc_appid(struct bio *bio)
+{
+	if (!bio->bi_blkg || bio->bi_blkg->blkcg->fc_app_id[0] == '\0')
+		return NULL;
+	return bio->bi_blkg->blkcg->fc_app_id;
+}
+EXPORT_SYMBOL_GPL(blkcg_get_fc_appid);
diff --git a/drivers/scsi/lpfc/lpfc_scsi.c b/drivers/scsi/lpfc/lpfc_scsi.c
index ba9dbb51b75f0..f6b83853f7eea 100644
--- a/drivers/scsi/lpfc/lpfc_scsi.c
+++ b/drivers/scsi/lpfc/lpfc_scsi.c
@@ -5528,7 +5528,9 @@ static char *lpfc_is_command_vm_io(struct scsi_cmnd *cmd)
 {
 	struct bio *bio = scsi_cmd_to_rq(cmd)->bio;
 
-	return bio ? blkcg_get_fc_appid(bio) : NULL;
+	if (!IS_ENABLED(CONFIG_BLK_CGROUP_FC_APPID) || !bio)
+		return NULL;
+	return blkcg_get_fc_appid(bio);
 }
 
 /**
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 652cd05b0924c..7a2f7de30173c 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -218,61 +218,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
 
 #endif	/* CONFIG_BLK_CGROUP */
 
-#ifdef CONFIG_BLK_CGROUP_FC_APPID
-/*
- * Sets the fc_app_id field associted to blkcg
- * @app_id: application identifier
- * @cgrp_id: cgroup id
- * @app_id_len: size of application identifier
- */
-static inline int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len)
-{
-	struct cgroup *cgrp;
-	struct cgroup_subsys_state *css;
-	struct blkcg *blkcg;
-	int ret  = 0;
-
-	if (app_id_len > FC_APPID_LEN)
-		return -EINVAL;
-
-	cgrp = cgroup_get_from_id(cgrp_id);
-	if (!cgrp)
-		return -ENOENT;
-	css = cgroup_get_e_css(cgrp, &io_cgrp_subsys);
-	if (!css) {
-		ret = -ENOENT;
-		goto out_cgrp_put;
-	}
-	blkcg = css_to_blkcg(css);
-	/*
-	 * There is a slight race condition on setting the appid.
-	 * Worst case an I/O may not find the right id.
-	 * This is no different from the I/O we let pass while obtaining
-	 * the vmid from the fabric.
-	 * Adding the overhead of a lock is not necessary.
-	 */
-	strlcpy(blkcg->fc_app_id, app_id, app_id_len);
-	css_put(css);
-out_cgrp_put:
-	cgroup_put(cgrp);
-	return ret;
-}
+int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len);
+char *blkcg_get_fc_appid(struct bio *bio);
 
-/**
- * blkcg_get_fc_appid - get the fc app identifier associated with a bio
- * @bio: target bio
- *
- * On success return the fc_app_id, on failure return NULL
- */
-static inline char *blkcg_get_fc_appid(struct bio *bio)
-{
-	if (bio && bio->bi_blkg &&
-		(bio->bi_blkg->blkcg->fc_app_id[0] != '\0'))
-		return bio->bi_blkg->blkcg->fc_app_id;
-	return NULL;
-}
-#else
-static inline int blkcg_set_fc_appid(char *buf, u64 id, size_t len) { return -EINVAL; }
-static inline char *blkcg_get_fc_appid(struct bio *bio) { return NULL; }
-#endif /*CONFIG_BLK_CGROUP_FC_APPID*/
 #endif	/* _BLK_CGROUP_H */
-- 
2.30.2

[PATCH 05/15] blk-cgroup: move blk_cgroup_congested out line

[Christoph Hellwig]

There is no urgent need to inline this function, so move it out of line.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c         | 20 ++++++++++++++++++++
 include/linux/blk-cgroup.h | 20 +-------------------
 2 files changed, 21 insertions(+), 19 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8dfe62786cd5f..97266ebde975b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1950,6 +1950,26 @@ void blk_cgroup_bio_start(struct bio *bio)
 	put_cpu();
 }
 
+bool blk_cgroup_congested(void)
+{
+	struct cgroup_subsys_state *css;
+	bool ret = false;
+
+	rcu_read_lock();
+	css = kthread_blkcg();
+	if (!css)
+		css = task_css(current, io_cgrp_id);
+	while (css) {
+		if (atomic_read(&css->cgroup->congestion_count)) {
+			ret = true;
+			break;
+		}
+		css = css->parent;
+	}
+	rcu_read_unlock();
+	return ret;
+}
+
 static int __init blkcg_init(void)
 {
 	blkcg_punt_bio_wq = alloc_workqueue("blkcg_punt_bio",
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 7a2f7de30173c..988965c1c27b8 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -135,25 +135,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
 	return NULL;
 }
 
-static inline bool blk_cgroup_congested(void)
-{
-	struct cgroup_subsys_state *css;
-	bool ret = false;
-
-	rcu_read_lock();
-	css = kthread_blkcg();
-	if (!css)
-		css = task_css(current, io_cgrp_id);
-	while (css) {
-		if (atomic_read(&css->cgroup->congestion_count)) {
-			ret = true;
-			break;
-		}
-		css = css->parent;
-	}
-	rcu_read_unlock();
-	return ret;
-}
+bool blk_cgroup_congested(void);
 
 /**
  * blkcg_parent - get the parent of a blkcg
-- 
2.30.2

[PATCH 06/15] blk-cgroup: move blkcg_{pin,unpin}_online out of line

[Christoph Hellwig]

Move these two functions out of line as there is no good reason
to inline them.  Also switch to passing a cgroup_subsys_state
instead of doing the conversion in the caller to prepare for making
the blkcg structure private to blk-cgroup.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c         | 88 ++++++++++++++++++++++++++++----------
 include/linux/blk-cgroup.h | 46 +-------------------
 mm/backing-dev.c           |  5 +--
 3 files changed, 69 insertions(+), 70 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 97266ebde975b..3af0d4a619550 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -155,6 +155,17 @@ static void blkg_async_bio_workfn(struct work_struct *work)
 		blk_finish_plug(&plug);
 }
 
+/**
+ * blkcg_parent - get the parent of a blkcg
+ * @blkcg: blkcg of interest
+ *
+ * Return the parent blkcg of @blkcg.  Can be called anytime.
+ */
+static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
+{
+	return css_to_blkcg(blkcg->css.parent);
+}
+
 /**
  * blkg_alloc - allocate a blkg
  * @blkcg: block cgroup the new blkg is associated with
@@ -1015,25 +1026,6 @@ static struct cftype blkcg_legacy_files[] = {
  *    This finally frees the blkcg.
  */
 
-/**
- * blkcg_css_offline - cgroup css_offline callback
- * @css: css of interest
- *
- * This function is called when @css is about to go away.  Here the cgwbs are
- * offlined first and only once writeback associated with the blkcg has
- * finished do we start step 2 (see above).
- */
-static void blkcg_css_offline(struct cgroup_subsys_state *css)
-{
-	struct blkcg *blkcg = css_to_blkcg(css);
-
-	/* this prevents anyone from attaching or migrating to this blkcg */
-	wb_blkcg_offline(blkcg);
-
-	/* put the base online pin allowing step 2 to be triggered */
-	blkcg_unpin_online(blkcg);
-}
-
 /**
  * blkcg_destroy_blkgs - responsible for shooting down blkgs
  * @blkcg: blkcg of interest
@@ -1045,7 +1037,7 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css)
  *
  * This is the blkcg counterpart of ioc_release_fn().
  */
-void blkcg_destroy_blkgs(struct blkcg *blkcg)
+static void blkcg_destroy_blkgs(struct blkcg *blkcg)
 {
 	might_sleep();
 
@@ -1075,6 +1067,57 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg)
 	spin_unlock_irq(&blkcg->lock);
 }
 
+/**
+ * blkcg_pin_online - pin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * While pinned, a blkcg is kept online.  This is primarily used to
+ * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
+ * while an associated cgwb is still active.
+ */
+void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css)
+{
+	refcount_inc(&css_to_blkcg(blkcg_css)->online_pin);
+}
+
+/**
+ * blkcg_unpin_online - unpin online state
+ * @blkcg_css: blkcg of interest
+ *
+ * This is primarily used to impedance-match blkg and cgwb lifetimes so
+ * that blkg doesn't go offline while an associated cgwb is still active.
+ * When this count goes to zero, all active cgwbs have finished so the
+ * blkcg can continue destruction by calling blkcg_destroy_blkgs().
+ */
+void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
+{
+	struct blkcg *blkcg = css_to_blkcg(blkcg_css);
+
+	do {
+		if (!refcount_dec_and_test(&blkcg->online_pin))
+			break;
+		blkcg_destroy_blkgs(blkcg);
+		blkcg = blkcg_parent(blkcg);
+	} while (blkcg);
+}
+
+/**
+ * blkcg_css_offline - cgroup css_offline callback
+ * @css: css of interest
+ *
+ * This function is called when @css is about to go away.  Here the cgwbs are
+ * offlined first and only once writeback associated with the blkcg has
+ * finished do we start step 2 (see above).
+ */
+static void blkcg_css_offline(struct cgroup_subsys_state *css)
+{
+	/* this prevents anyone from attaching or migrating to this blkcg */
+	wb_blkcg_offline(css_to_blkcg(css));
+
+	/* put the base online pin allowing step 2 to be triggered */
+	blkcg_unpin_online(css);
+}
+
 static void blkcg_css_free(struct cgroup_subsys_state *css)
 {
 	struct blkcg *blkcg = css_to_blkcg(css);
@@ -1163,8 +1206,7 @@ blkcg_css_alloc(struct cgroup_subsys_state *parent_css)
 
 static int blkcg_css_online(struct cgroup_subsys_state *css)
 {
-	struct blkcg *blkcg = css_to_blkcg(css);
-	struct blkcg *parent = blkcg_parent(blkcg);
+	struct blkcg *parent = blkcg_parent(css_to_blkcg(css));
 
 	/*
 	 * blkcg_pin_online() is used to delay blkcg offline so that blkgs
@@ -1172,7 +1214,7 @@ static int blkcg_css_online(struct cgroup_subsys_state *css)
 	 * parent so that offline always happens towards the root.
 	 */
 	if (parent)
-		blkcg_pin_online(parent);
+		blkcg_pin_online(css);
 	return 0;
 }
 
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 988965c1c27b8..0fb7459096e9f 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -111,7 +111,6 @@ struct blkcg_gq {
 
 extern struct cgroup_subsys_state * const blkcg_root_css;
 
-void blkcg_destroy_blkgs(struct blkcg *blkcg);
 void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay);
 void blkcg_maybe_throttle_current(void);
 
@@ -136,49 +135,8 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
 }
 
 bool blk_cgroup_congested(void);
-
-/**
- * blkcg_parent - get the parent of a blkcg
- * @blkcg: blkcg of interest
- *
- * Return the parent blkcg of @blkcg.  Can be called anytime.
- */
-static inline struct blkcg *blkcg_parent(struct blkcg *blkcg)
-{
-	return css_to_blkcg(blkcg->css.parent);
-}
-
-/**
- * blkcg_pin_online - pin online state
- * @blkcg: blkcg of interest
- *
- * While pinned, a blkcg is kept online.  This is primarily used to
- * impedance-match blkg and cgwb lifetimes so that blkg doesn't go offline
- * while an associated cgwb is still active.
- */
-static inline void blkcg_pin_online(struct blkcg *blkcg)
-{
-	refcount_inc(&blkcg->online_pin);
-}
-
-/**
- * blkcg_unpin_online - unpin online state
- * @blkcg: blkcg of interest
- *
- * This is primarily used to impedance-match blkg and cgwb lifetimes so
- * that blkg doesn't go offline while an associated cgwb is still active.
- * When this count goes to zero, all active cgwbs have finished so the
- * blkcg can continue destruction by calling blkcg_destroy_blkgs().
- */
-static inline void blkcg_unpin_online(struct blkcg *blkcg)
-{
-	do {
-		if (!refcount_dec_and_test(&blkcg->online_pin))
-			break;
-		blkcg_destroy_blkgs(blkcg);
-		blkcg = blkcg_parent(blkcg);
-	} while (blkcg);
-}
+void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css);
+void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css);
 
 #else	/* CONFIG_BLK_CGROUP */
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7176af65b103a..93cddbcd4eb83 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -390,7 +390,6 @@ static void cgwb_release_workfn(struct work_struct *work)
 {
 	struct bdi_writeback *wb = container_of(work, struct bdi_writeback,
 						release_work);
-	struct blkcg *blkcg = css_to_blkcg(wb->blkcg_css);
 	struct backing_dev_info *bdi = wb->bdi;
 
 	mutex_lock(&wb->bdi->cgwb_release_mutex);
@@ -401,7 +400,7 @@ static void cgwb_release_workfn(struct work_struct *work)
 	mutex_unlock(&wb->bdi->cgwb_release_mutex);
 
 	/* triggers blkg destruction if no online users left */
-	blkcg_unpin_online(blkcg);
+	blkcg_unpin_online(wb->blkcg_css);
 
 	fprop_local_destroy_percpu(&wb->memcg_completions);
 
@@ -511,7 +510,7 @@ static int cgwb_create(struct backing_dev_info *bdi,
 			list_add_tail_rcu(&wb->bdi_node, &bdi->wb_list);
 			list_add(&wb->memcg_node, memcg_cgwb_list);
 			list_add(&wb->blkcg_node, blkcg_cgwb_list);
-			blkcg_pin_online(blkcg);
+			blkcg_pin_online(blkcg_css);
 			css_get(memcg_css);
 			css_get(blkcg_css);
 		}
-- 
2.30.2

[PATCH 07/15] blk-cgroup: move struct blkcg to block/blk-cgroup.h

[Christoph Hellwig]

There is no real need to expose the blkcg structure to the whole kernel.
Move it to the private header an expose a helper to let the writeback
code access the cgwb_list member.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c          |  9 ++++++++-
 block/blk-cgroup.h          | 28 ++++++++++++++++++++++++++++
 include/linux/backing-dev.h |  6 ++----
 include/linux/blk-cgroup.h  | 32 +-------------------------------
 mm/backing-dev.c            | 13 ++++++-------
 5 files changed, 45 insertions(+), 43 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 3af0d4a619550..bb52797c02bd7 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1005,6 +1005,13 @@ static struct cftype blkcg_legacy_files[] = {
 	{ }	/* terminate */
 };
 
+#ifdef CONFIG_CGROUP_WRITEBACK
+struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css)
+{
+	return &css_to_blkcg(css)->cgwb_list;
+}
+#endif
+
 /*
  * blkcg destruction is a three-stage process.
  *
@@ -1112,7 +1119,7 @@ void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css)
 static void blkcg_css_offline(struct cgroup_subsys_state *css)
 {
 	/* this prevents anyone from attaching or migrating to this blkcg */
-	wb_blkcg_offline(css_to_blkcg(css));
+	wb_blkcg_offline(css);
 
 	/* put the base online pin allowing step 2 to be triggered */
 	blkcg_unpin_online(css);
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 49e88fc9cc391..b00fb1169e7ce 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -17,10 +17,38 @@
 #include <linux/blk-cgroup.h>
 #include <linux/blk-mq.h>
 
+struct blkcg_gq;
+struct blkg_policy_data;
+
+
 /* percpu_counter batch for blkg_[rw]stats, per-cpu drift doesn't matter */
 #define BLKG_STAT_CPU_BATCH	(INT_MAX / 2)
 
 #ifdef CONFIG_BLK_CGROUP
+struct blkcg {
+	struct cgroup_subsys_state	css;
+	spinlock_t			lock;
+	refcount_t			online_pin;
+
+	struct radix_tree_root		blkg_tree;
+	struct blkcg_gq	__rcu		*blkg_hint;
+	struct hlist_head		blkg_list;
+
+	struct blkcg_policy_data	*cpd[BLKCG_MAX_POLS];
+
+	struct list_head		all_blkcgs_node;
+#ifdef CONFIG_BLK_CGROUP_FC_APPID
+	char                            fc_app_id[FC_APPID_LEN];
+#endif
+#ifdef CONFIG_CGROUP_WRITEBACK
+	struct list_head		cgwb_list;
+#endif
+};
+
+static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
+{
+	return css ? container_of(css, struct blkcg, css) : NULL;
+}
 
 /*
  * A blkcg_gq (blkg) is association between a block cgroup (blkcg) and a
diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 87ce24d238f34..2bd073fa6bb53 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -17,8 +17,6 @@
 #include <linux/backing-dev-defs.h>
 #include <linux/slab.h>
 
-struct blkcg;
-
 static inline struct backing_dev_info *bdi_get(struct backing_dev_info *bdi)
 {
 	kref_get(&bdi->refcnt);
@@ -154,7 +152,7 @@ struct bdi_writeback *wb_get_create(struct backing_dev_info *bdi,
 				    struct cgroup_subsys_state *memcg_css,
 				    gfp_t gfp);
 void wb_memcg_offline(struct mem_cgroup *memcg);
-void wb_blkcg_offline(struct blkcg *blkcg);
+void wb_blkcg_offline(struct cgroup_subsys_state *css);
 
 /**
  * inode_cgwb_enabled - test whether cgroup writeback is enabled on an inode
@@ -378,7 +376,7 @@ static inline void wb_memcg_offline(struct mem_cgroup *memcg)
 {
 }
 
-static inline void wb_blkcg_offline(struct blkcg *blkcg)
+static inline void wb_blkcg_offline(struct cgroup_subsys_state *css)
 {
 }
 
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 0fb7459096e9f..d7b1880950402 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -37,29 +37,6 @@ enum blkg_iostat_type {
 	BLKG_IOSTAT_NR,
 };
 
-struct blkcg_gq;
-struct blkg_policy_data;
-
-struct blkcg {
-	struct cgroup_subsys_state	css;
-	spinlock_t			lock;
-	refcount_t			online_pin;
-
-	struct radix_tree_root		blkg_tree;
-	struct blkcg_gq	__rcu		*blkg_hint;
-	struct hlist_head		blkg_list;
-
-	struct blkcg_policy_data	*cpd[BLKCG_MAX_POLS];
-
-	struct list_head		all_blkcgs_node;
-#ifdef CONFIG_BLK_CGROUP_FC_APPID
-	char                            fc_app_id[FC_APPID_LEN];
-#endif
-#ifdef CONFIG_CGROUP_WRITEBACK
-	struct list_head		cgwb_list;
-#endif
-};
-
 struct blkg_iostat {
 	u64				bytes[BLKG_IOSTAT_NR];
 	u64				ios[BLKG_IOSTAT_NR];
@@ -114,11 +91,6 @@ extern struct cgroup_subsys_state * const blkcg_root_css;
 void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay);
 void blkcg_maybe_throttle_current(void);
 
-static inline struct blkcg *css_to_blkcg(struct cgroup_subsys_state *css)
-{
-	return css ? container_of(css, struct blkcg, css) : NULL;
-}
-
 /**
  * bio_blkcg - grab the blkcg associated with a bio
  * @bio: target bio
@@ -137,12 +109,10 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
 bool blk_cgroup_congested(void);
 void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css);
 void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css);
+struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css);
 
 #else	/* CONFIG_BLK_CGROUP */
 
-struct blkcg {
-};
-
 struct blkcg_gq {
 };
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 93cddbcd4eb83..98f8f62e52ca5 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -445,7 +445,6 @@ static int cgwb_create(struct backing_dev_info *bdi,
 {
 	struct mem_cgroup *memcg;
 	struct cgroup_subsys_state *blkcg_css;
-	struct blkcg *blkcg;
 	struct list_head *memcg_cgwb_list, *blkcg_cgwb_list;
 	struct bdi_writeback *wb;
 	unsigned long flags;
@@ -453,9 +452,8 @@ static int cgwb_create(struct backing_dev_info *bdi,
 
 	memcg = mem_cgroup_from_css(memcg_css);
 	blkcg_css = cgroup_get_e_css(memcg_css->cgroup, &io_cgrp_subsys);
-	blkcg = css_to_blkcg(blkcg_css);
 	memcg_cgwb_list = &memcg->cgwb_list;
-	blkcg_cgwb_list = &blkcg->cgwb_list;
+	blkcg_cgwb_list = blkcg_get_cgwb_list(blkcg_css);
 
 	/* look up again under lock and discard on blkcg mismatch */
 	spin_lock_irqsave(&cgwb_lock, flags);
@@ -723,18 +721,19 @@ void wb_memcg_offline(struct mem_cgroup *memcg)
 
 /**
  * wb_blkcg_offline - kill all wb's associated with a blkcg being offlined
- * @blkcg: blkcg being offlined
+ * @css: blkcg being offlined
  *
  * Also prevents creation of any new wb's associated with @blkcg.
  */
-void wb_blkcg_offline(struct blkcg *blkcg)
+void wb_blkcg_offline(struct cgroup_subsys_state *css)
 {
 	struct bdi_writeback *wb, *next;
+	struct list_head *list = blkcg_get_cgwb_list(css);
 
 	spin_lock_irq(&cgwb_lock);
-	list_for_each_entry_safe(wb, next, &blkcg->cgwb_list, blkcg_node)
+	list_for_each_entry_safe(wb, next, list, blkcg_node)
 		cgwb_kill(wb);
-	blkcg->cgwb_list.next = NULL;	/* prevent new wb's */
+	list->next = NULL;	/* prevent new wb's */
 	spin_unlock_irq(&cgwb_lock);
 }
 
-- 
2.30.2

[PATCH 08/15] blktrace: cleanup the __trace_note_message interface

[Christoph Hellwig]

Pass the cgroup_subsys_state instead of a the blkg so that blktrace
doesn't need to poke into blk-cgroup internals, and give the name a
blk prefix as the current name is way too generic for a public
interface.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/bfq-iosched.h          |  4 ++--
 block/blk-throttle.c         |  2 +-
 include/linux/blktrace_api.h | 10 ++++------
 kernel/trace/blktrace.c      | 20 ++++++++++----------
 4 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index 978ef5d6fe6ab..b18d6c31c2251 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -1102,13 +1102,13 @@ struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
 		break;							\
 	bfq_bfqq_name((bfqq), pid_str, MAX_BFQQ_NAME_LENGTH);		\
 	blk_add_cgroup_trace_msg((bfqd)->queue,				\
-			bfqg_to_blkg(bfqq_group(bfqq))->blkcg,		\
+			&bfqg_to_blkg(bfqq_group(bfqq))->blkcg->css,	\
 			"%s " fmt, pid_str, ##args);			\
 } while (0)
 
 #define bfq_log_bfqg(bfqd, bfqg, fmt, args...)	do {			\
 	blk_add_cgroup_trace_msg((bfqd)->queue,				\
-		bfqg_to_blkg(bfqg)->blkcg, fmt, ##args);		\
+		&bfqg_to_blkg(bfqg)->blkcg->css, fmt, ##args);		\
 } while (0)
 
 #else /* CONFIG_BFQ_GROUP_IOSCHED */
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 469c483719bea..447e1b8722f7a 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -227,7 +227,7 @@ static unsigned int tg_iops_limit(struct throtl_grp *tg, int rw)
 		break;							\
 	if ((__tg)) {							\
 		blk_add_cgroup_trace_msg(__td->queue,			\
-			tg_to_blkg(__tg)->blkcg, "throtl " fmt, ##args);\
+			&tg_to_blkg(__tg)->blkcg->css, "throtl " fmt, ##args);\
 	} else {							\
 		blk_add_trace_msg(__td->queue, "throtl " fmt, ##args);	\
 	}								\
diff --git a/include/linux/blktrace_api.h b/include/linux/blktrace_api.h
index 22501a293fa54..623e22492afa5 100644
--- a/include/linux/blktrace_api.h
+++ b/include/linux/blktrace_api.h
@@ -27,12 +27,10 @@ struct blk_trace {
 	atomic_t dropped;
 };
 
-struct blkcg;
-
 extern int blk_trace_ioctl(struct block_device *, unsigned, char __user *);
 extern void blk_trace_shutdown(struct request_queue *);
-extern __printf(3, 4)
-void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *fmt, ...);
+__printf(3, 4) void __blk_trace_note_message(struct blk_trace *bt,
+		struct cgroup_subsys_state *css, const char *fmt, ...);
 
 /**
  * blk_add_trace_msg - Add a (simple) message to the blktrace stream
@@ -47,14 +45,14 @@ void __trace_note_message(struct blk_trace *, struct blkcg *blkcg, const char *f
  *     NOTE: Can not use 'static inline' due to presence of var args...
  *
  **/
-#define blk_add_cgroup_trace_msg(q, cg, fmt, ...)			\
+#define blk_add_cgroup_trace_msg(q, css, fmt, ...)			\
 	do {								\
 		struct blk_trace *bt;					\
 									\
 		rcu_read_lock();					\
 		bt = rcu_dereference((q)->blk_trace);			\
 		if (unlikely(bt))					\
-			__trace_note_message(bt, cg, fmt, ##__VA_ARGS__);\
+			__blk_trace_note_message(bt, css, fmt, ##__VA_ARGS__);\
 		rcu_read_unlock();					\
 	} while (0)
 #define blk_add_trace_msg(q, fmt, ...)					\
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 4d5629196d01d..9ef349ac49c01 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -145,13 +145,14 @@ static void trace_note_time(struct blk_trace *bt)
 	local_irq_restore(flags);
 }
 
-void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
-	const char *fmt, ...)
+void __blk_trace_note_message(struct blk_trace *bt,
+		struct cgroup_subsys_state *css, const char *fmt, ...)
 {
 	int n;
 	va_list args;
 	unsigned long flags;
 	char *buf;
+	u64 cgid = 0;
 
 	if (unlikely(bt->trace_state != Blktrace_running &&
 		     !blk_tracer_enabled))
@@ -170,17 +171,16 @@ void __trace_note_message(struct blk_trace *bt, struct blkcg *blkcg,
 	n = vscnprintf(buf, BLK_TN_MAX_MSG, fmt, args);
 	va_end(args);
 
-	if (!(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
-		blkcg = NULL;
 #ifdef CONFIG_BLK_CGROUP
-	trace_note(bt, current->pid, BLK_TN_MESSAGE, buf, n,
-		   blkcg ? cgroup_id(blkcg->css.cgroup) : 1);
-#else
-	trace_note(bt, current->pid, BLK_TN_MESSAGE, buf, n, 0);
+	if (css && (blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
+		cgid = cgroup_id(css->cgroup);
+	else
+		cgid = 1;
 #endif
+	trace_note(bt, current->pid, BLK_TN_MESSAGE, buf, n, cgid);
 	local_irq_restore(flags);
 }
-EXPORT_SYMBOL_GPL(__trace_note_message);
+EXPORT_SYMBOL_GPL(__blk_trace_note_message);
 
 static int act_log_check(struct blk_trace *bt, u32 what, sector_t sector,
 			 pid_t pid)
@@ -411,7 +411,7 @@ static ssize_t blk_msg_write(struct file *filp, const char __user *buffer,
 		return PTR_ERR(msg);
 
 	bt = filp->private_data;
-	__trace_note_message(bt, NULL, "%s", msg);
+	__blk_trace_note_message(bt, NULL, "%s", msg);
 	kfree(msg);
 
 	return count;
-- 
2.30.2

[PATCH 09/15] blk-cgroup: replace bio_blkcg with bio_blkcg_css

[Christoph Hellwig]

All callers of bio_blkcg actually want the CSS, so replace it with an
interface that does return the CSS.  This now allows to move
struct blkcg_gq to block/blk-cgroup.h instead of exposing it in a
public header.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c         | 18 ++++++++-
 block/blk-cgroup.h         | 67 ++++++++++++++++++++++++++++--
 drivers/block/loop.c       | 12 +++---
 include/linux/blk-cgroup.h | 83 +++-----------------------------------
 kernel/trace/blktrace.c    |  6 ++-
 5 files changed, 97 insertions(+), 89 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index bb52797c02bd7..8e32cc494808d 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -155,6 +155,22 @@ static void blkg_async_bio_workfn(struct work_struct *work)
 		blk_finish_plug(&plug);
 }
 
+/**
+ * bio_blkcg_css - return the blkcg CSS associated with a bio
+ * @bio: target bio
+ *
+ * This returns the CSS for the blkcg associated with a bio, or %NULL if not
+ * associated. Callers are expected to either handle %NULL or know association
+ * has been done prior to calling this.
+ */
+struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
+{
+	if (!bio || !bio->bi_blkg)
+		return NULL;
+	return &bio->bi_blkg->blkcg->css;
+}
+EXPORT_SYMBOL_GPL(bio_blkcg_css);
+
 /**
  * blkcg_parent - get the parent of a blkcg
  * @blkcg: blkcg of interest
@@ -1938,7 +1954,7 @@ void bio_associate_blkg(struct bio *bio)
 	rcu_read_lock();
 
 	if (bio->bi_blkg)
-		css = &bio_blkcg(bio)->css;
+		css = bio_blkcg_css(bio);
 	else
 		css = blkcg_css();
 
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index b00fb1169e7ce..03405ddf2a7ba 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -25,6 +25,64 @@ struct blkg_policy_data;
 #define BLKG_STAT_CPU_BATCH	(INT_MAX / 2)
 
 #ifdef CONFIG_BLK_CGROUP
+
+enum blkg_iostat_type {
+	BLKG_IOSTAT_READ,
+	BLKG_IOSTAT_WRITE,
+	BLKG_IOSTAT_DISCARD,
+
+	BLKG_IOSTAT_NR,
+};
+
+struct blkg_iostat {
+	u64				bytes[BLKG_IOSTAT_NR];
+	u64				ios[BLKG_IOSTAT_NR];
+};
+
+struct blkg_iostat_set {
+	struct u64_stats_sync		sync;
+	struct blkg_iostat		cur;
+	struct blkg_iostat		last;
+};
+
+/* association between a blk cgroup and a request queue */
+struct blkcg_gq {
+	/* Pointer to the associated request_queue */
+	struct request_queue		*q;
+	struct list_head		q_node;
+	struct hlist_node		blkcg_node;
+	struct blkcg			*blkcg;
+
+	/* all non-root blkcg_gq's are guaranteed to have access to parent */
+	struct blkcg_gq			*parent;
+
+	/* reference count */
+	struct percpu_ref		refcnt;
+
+	/* is this blkg online? protected by both blkcg and q locks */
+	bool				online;
+
+	struct blkg_iostat_set __percpu	*iostat_cpu;
+	struct blkg_iostat_set		iostat;
+
+	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
+
+	spinlock_t			async_bio_lock;
+	struct bio_list			async_bios;
+	union {
+		struct work_struct	async_bio_work;
+		struct work_struct	free_work;
+	};
+
+	atomic_t			use_delay;
+	atomic64_t			delay_nsec;
+	atomic64_t			delay_start;
+	u64				last_delay;
+	int				last_use;
+
+	struct rcu_head			rcu_head;
+};
+
 struct blkcg {
 	struct cgroup_subsys_state	css;
 	spinlock_t			lock;
@@ -173,9 +231,9 @@ static inline struct cgroup_subsys_state *blkcg_css(void)
  *
  * In order to avoid priority inversions we sometimes need to issue a bio as if
  * it were attached to the root blkg, and then backcharge to the actual owning
- * blkg.  The idea is we do bio_blkcg() to look up the actual context for the
- * bio and attach the appropriate blkg to the bio.  Then we call this helper and
- * if it is true run with the root blkg for that queue and then do any
+ * blkg.  The idea is we do bio_blkcg_css() to look up the actual context for
+ * the bio and attach the appropriate blkg to the bio.  Then we call this helper
+ * and if it is true run with the root blkg for that queue and then do any
  * backcharging to the originating cgroup once the io is complete.
  */
 static inline bool bio_issue_as_root_blkg(struct bio *bio)
@@ -464,6 +522,9 @@ struct blkcg_policy_data {
 struct blkcg_policy {
 };
 
+struct blkcg {
+};
+
 #ifdef CONFIG_BLOCK
 
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 976cf987b3920..fabcf647306af 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1829,12 +1829,14 @@ static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
 	cmd->blkcg_css = NULL;
 	cmd->memcg_css = NULL;
 #ifdef CONFIG_BLK_CGROUP
-	if (rq->bio && rq->bio->bi_blkg) {
-		cmd->blkcg_css = &bio_blkcg(rq->bio)->css;
+	if (rq->bio) {
+		cmd->blkcg_css = bio_blkcg_css(rq->bio);
 #ifdef CONFIG_MEMCG
-		cmd->memcg_css =
-			cgroup_get_e_css(cmd->blkcg_css->cgroup,
-					&memory_cgrp_subsys);
+		if (cmd->blkcg_css) {
+			cmd->memcg_css =
+				cgroup_get_e_css(cmd->blkcg_css->cgroup,
+						&memory_cgrp_subsys);
+		}
 #endif
 	}
 #endif
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index d7b1880950402..97c7968e32040 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -28,94 +28,18 @@
 #define FC_APPID_LEN              129
 
 #ifdef CONFIG_BLK_CGROUP
-
-enum blkg_iostat_type {
-	BLKG_IOSTAT_READ,
-	BLKG_IOSTAT_WRITE,
-	BLKG_IOSTAT_DISCARD,
-
-	BLKG_IOSTAT_NR,
-};
-
-struct blkg_iostat {
-	u64				bytes[BLKG_IOSTAT_NR];
-	u64				ios[BLKG_IOSTAT_NR];
-};
-
-struct blkg_iostat_set {
-	struct u64_stats_sync		sync;
-	struct blkg_iostat		cur;
-	struct blkg_iostat		last;
-};
-
-/* association between a blk cgroup and a request queue */
-struct blkcg_gq {
-	/* Pointer to the associated request_queue */
-	struct request_queue		*q;
-	struct list_head		q_node;
-	struct hlist_node		blkcg_node;
-	struct blkcg			*blkcg;
-
-	/* all non-root blkcg_gq's are guaranteed to have access to parent */
-	struct blkcg_gq			*parent;
-
-	/* reference count */
-	struct percpu_ref		refcnt;
-
-	/* is this blkg online? protected by both blkcg and q locks */
-	bool				online;
-
-	struct blkg_iostat_set __percpu	*iostat_cpu;
-	struct blkg_iostat_set		iostat;
-
-	struct blkg_policy_data		*pd[BLKCG_MAX_POLS];
-
-	spinlock_t			async_bio_lock;
-	struct bio_list			async_bios;
-	union {
-		struct work_struct	async_bio_work;
-		struct work_struct	free_work;
-	};
-
-	atomic_t			use_delay;
-	atomic64_t			delay_nsec;
-	atomic64_t			delay_start;
-	u64				last_delay;
-	int				last_use;
-
-	struct rcu_head			rcu_head;
-};
-
 extern struct cgroup_subsys_state * const blkcg_root_css;
 
 void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay);
 void blkcg_maybe_throttle_current(void);
-
-/**
- * bio_blkcg - grab the blkcg associated with a bio
- * @bio: target bio
- *
- * This returns the blkcg associated with a bio, %NULL if not associated.
- * Callers are expected to either handle %NULL or know association has been
- * done prior to calling this.
- */
-static inline struct blkcg *bio_blkcg(struct bio *bio)
-{
-	if (bio && bio->bi_blkg)
-		return bio->bi_blkg->blkcg;
-	return NULL;
-}
-
 bool blk_cgroup_congested(void);
 void blkcg_pin_online(struct cgroup_subsys_state *blkcg_css);
 void blkcg_unpin_online(struct cgroup_subsys_state *blkcg_css);
 struct list_head *blkcg_get_cgwb_list(struct cgroup_subsys_state *css);
+struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio);
 
 #else	/* CONFIG_BLK_CGROUP */
 
-struct blkcg_gq {
-};
-
 #define blkcg_root_css	((struct cgroup_subsys_state *)ERR_PTR(-EINVAL))
 
 static inline void blkcg_maybe_throttle_current(void) { }
@@ -123,7 +47,10 @@ static inline bool blk_cgroup_congested(void) { return false; }
 
 #ifdef CONFIG_BLOCK
 static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }
-static inline struct blkcg *bio_blkcg(struct bio *bio) { return NULL; }
+static inline struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
+{
+	return NULL;
+}
 #endif /* CONFIG_BLOCK */
 
 #endif	/* CONFIG_BLK_CGROUP */
diff --git a/kernel/trace/blktrace.c b/kernel/trace/blktrace.c
index 9ef349ac49c01..10a32b0f2deb6 100644
--- a/kernel/trace/blktrace.c
+++ b/kernel/trace/blktrace.c
@@ -783,6 +783,7 @@ void blk_trace_shutdown(struct request_queue *q)
 #ifdef CONFIG_BLK_CGROUP
 static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 {
+	struct cgroup_subsys_state *blkcg_css;
 	struct blk_trace *bt;
 
 	/* We don't use the 'bt' value here except as an optimization... */
@@ -790,9 +791,10 @@ static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
 	if (!bt || !(blk_tracer_flags.val & TRACE_BLK_OPT_CGROUP))
 		return 0;
 
-	if (!bio->bi_blkg)
+	blkcg_css = bio_blkcg_css(bio);
+	if (!blkcg_css)
 		return 0;
-	return cgroup_id(bio_blkcg(bio)->css.cgroup);
+	return cgroup_id(blkcg_css->cgroup);
 }
 #else
 static u64 blk_trace_bio_get_cgid(struct request_queue *q, struct bio *bio)
-- 
2.30.2

[PATCH 10/15] blk-cgroup: remove pointless CONFIG_BLOCK ifdefs

[Christoph Hellwig]

No need to make BLK_CGROUP stubs conditional on CONFIG_BLOCK as they
can't be used without that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.h         | 3 ---
 include/linux/blk-cgroup.h | 4 ----
 2 files changed, 7 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 03405ddf2a7ba..a948f4eb0bff8 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -525,8 +525,6 @@ struct blkcg_policy {
 struct blkcg {
 };
 
-#ifdef CONFIG_BLOCK
-
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 { return NULL; }
@@ -554,7 +552,6 @@ static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { r
 #define blk_queue_for_each_rl(rl, q)	\
 	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
 
-#endif	/* CONFIG_BLOCK */
 #endif	/* CONFIG_BLK_CGROUP */
 
 #endif /* _BLK_CGROUP_PRIVATE_H */
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 97c7968e32040..abbfa97d6d46f 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -44,15 +44,11 @@ struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio);
 
 static inline void blkcg_maybe_throttle_current(void) { }
 static inline bool blk_cgroup_congested(void) { return false; }
-
-#ifdef CONFIG_BLOCK
 static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }
 static inline struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
 {
 	return NULL;
 }
-#endif /* CONFIG_BLOCK */
-
 #endif	/* CONFIG_BLK_CGROUP */
 
 int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len);
-- 
2.30.2

[PATCH 10/15] blk-cgroup: remove pointless CONFIG_BLOCK ifdefs

[Christoph Hellwig]

No need to make BLK_CGROUP stubs conditional on CONFIG_BLOCK as they
can't be used without that.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 block/blk-cgroup.h         | 3 ---
 include/linux/blk-cgroup.h | 4 ----
 2 files changed, 7 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 03405ddf2a7ba..a948f4eb0bff8 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -525,8 +525,6 @@ struct blkcg_policy {
 struct blkcg {
 };
 
-#ifdef CONFIG_BLOCK
-
 static inline struct blkcg_gq *blkg_lookup(struct blkcg *blkcg, void *key) { return NULL; }
 static inline struct blkcg_gq *blk_queue_root_blkg(struct request_queue *q)
 { return NULL; }
@@ -554,7 +552,6 @@ static inline bool blk_cgroup_mergeable(struct request *rq, struct bio *bio) { r
 #define blk_queue_for_each_rl(rl, q)	\
 	for ((rl) = &(q)->root_rl; (rl); (rl) = NULL)
 
-#endif	/* CONFIG_BLOCK */
 #endif	/* CONFIG_BLK_CGROUP */
 
 #endif /* _BLK_CGROUP_PRIVATE_H */
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index 97c7968e32040..abbfa97d6d46f 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -44,15 +44,11 @@ struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio);
 
 static inline void blkcg_maybe_throttle_current(void) { }
 static inline bool blk_cgroup_congested(void) { return false; }
-
-#ifdef CONFIG_BLOCK
 static inline void blkcg_schedule_throttle(struct request_queue *q, bool use_memdelay) { }
 static inline struct cgroup_subsys_state *bio_blkcg_css(struct bio *bio)
 {
 	return NULL;
 }
-#endif /* CONFIG_BLOCK */
-
 #endif	/* CONFIG_BLK_CGROUP */
 
 int blkcg_set_fc_appid(char *app_id, u64 cgrp_id, size_t app_id_len);
-- 
2.30.2

[PATCH 11/15] blk-cgroup: remove unneeded includes from <linux/blk-cgroup.h>

[Christoph Hellwig]

Remove all the includes that aren't actually needed from
<linux/blk-cgroup.h> and push them to the actual source files where
needed.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.h         |  2 ++
 include/linux/blk-cgroup.h | 15 +++++----------
 mm/backing-dev.c           |  1 +
 mm/readahead.c             |  1 +
 mm/swapfile.c              |  1 +
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index a948f4eb0bff8..62ed8ed50b6e3 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -15,6 +15,8 @@
  */
 
 #include <linux/blk-cgroup.h>
+#include <linux/cgroup.h>
+#include <linux/kthread.h>
 #include <linux/blk-mq.h>
 
 struct blkcg_gq;
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index abbfa97d6d46f..9f40dbc65f82c 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -14,16 +14,11 @@
  * 	              Nauman Rafique <nauman@google.com>
  */
 
-#include <linux/cgroup.h>
-#include <linux/percpu.h>
-#include <linux/percpu_counter.h>
-#include <linux/u64_stats_sync.h>
-#include <linux/seq_file.h>
-#include <linux/radix-tree.h>
-#include <linux/blkdev.h>
-#include <linux/atomic.h>
-#include <linux/kthread.h>
-#include <linux/fs.h>
+#include <linux/types.h>
+
+struct bio;
+struct cgroup_subsys_state;
+struct request_queue;
 
 #define FC_APPID_LEN              129
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 98f8f62e52ca5..ff60bd7d74e07 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include <linux/blkdev.h>
 #include <linux/wait.h>
 #include <linux/rbtree.h>
 #include <linux/kthread.h>
diff --git a/mm/readahead.c b/mm/readahead.c
index 8e3775829513e..c93671a2bf0f7 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -113,6 +113,7 @@
  * ->readpage() which may be less efficient.
  */
 
+#include <linux/blkdev.h>
 #include <linux/kernel.h>
 #include <linux/dax.h>
 #include <linux/gfp.h>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a2b31fea0c42e..981a6e85c88e7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -6,6 +6,7 @@
  *  Swap reorganised 29.12.95, Stephen Tweedie
  */
 
+#include <linux/blkdev.h>
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/task.h>
-- 
2.30.2

[PATCH 11/15] blk-cgroup: remove unneeded includes from <linux/blk-cgroup.h>

[Christoph Hellwig]

Remove all the includes that aren't actually needed from
<linux/blk-cgroup.h> and push them to the actual source files where
needed.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 block/blk-cgroup.h         |  2 ++
 include/linux/blk-cgroup.h | 15 +++++----------
 mm/backing-dev.c           |  1 +
 mm/readahead.c             |  1 +
 mm/swapfile.c              |  1 +
 5 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index a948f4eb0bff8..62ed8ed50b6e3 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -15,6 +15,8 @@
  */
 
 #include <linux/blk-cgroup.h>
+#include <linux/cgroup.h>
+#include <linux/kthread.h>
 #include <linux/blk-mq.h>
 
 struct blkcg_gq;
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index abbfa97d6d46f..9f40dbc65f82c 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -14,16 +14,11 @@
  * 	              Nauman Rafique <nauman-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
  */
 
-#include <linux/cgroup.h>
-#include <linux/percpu.h>
-#include <linux/percpu_counter.h>
-#include <linux/u64_stats_sync.h>
-#include <linux/seq_file.h>
-#include <linux/radix-tree.h>
-#include <linux/blkdev.h>
-#include <linux/atomic.h>
-#include <linux/kthread.h>
-#include <linux/fs.h>
+#include <linux/types.h>
+
+struct bio;
+struct cgroup_subsys_state;
+struct request_queue;
 
 #define FC_APPID_LEN              129
 
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 98f8f62e52ca5..ff60bd7d74e07 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 
+#include <linux/blkdev.h>
 #include <linux/wait.h>
 #include <linux/rbtree.h>
 #include <linux/kthread.h>
diff --git a/mm/readahead.c b/mm/readahead.c
index 8e3775829513e..c93671a2bf0f7 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -113,6 +113,7 @@
  * ->readpage() which may be less efficient.
  */
 
+#include <linux/blkdev.h>
 #include <linux/kernel.h>
 #include <linux/dax.h>
 #include <linux/gfp.h>
diff --git a/mm/swapfile.c b/mm/swapfile.c
index a2b31fea0c42e..981a6e85c88e7 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -6,6 +6,7 @@
  *  Swap reorganised 29.12.95, Stephen Tweedie
  */
 
+#include <linux/blkdev.h>
 #include <linux/mm.h>
 #include <linux/sched/mm.h>
 #include <linux/sched/task.h>
-- 
2.30.2

[PATCH 12/15] blk-cgroup: move blkcg_css to blk-cgroup.c

[Christoph Hellwig]

blkcg_css is only used in blk-cgroup.c, so move it there.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c | 17 +++++++++++++++++
 block/blk-cgroup.h | 17 -----------------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8e32cc494808d..8da00ddc1766e 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -59,6 +59,23 @@ static struct workqueue_struct *blkcg_punt_bio_wq;
 
 #define BLKG_DESTROY_BATCH_SIZE  64
 
+/**
+ * blkcg_css - find the current css
+ *
+ * Find the css associated with either the kthread or the current task.
+ * This may return a dying css, so it is up to the caller to use tryget logic
+ * to confirm it is alive and well.
+ */
+static struct cgroup_subsys_state *blkcg_css(void)
+{
+	struct cgroup_subsys_state *css;
+
+	css = kthread_blkcg();
+	if (css)
+		return css;
+	return task_css(current, io_cgrp_id);
+}
+
 static bool blkcg_policy_enabled(struct request_queue *q,
 				 const struct blkcg_policy *pol)
 {
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 62ed8ed50b6e3..bb670e53a1de2 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -210,23 +210,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		   char *input, struct blkg_conf_ctx *ctx);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 
-/**
- * blkcg_css - find the current css
- *
- * Find the css associated with either the kthread or the current task.
- * This may return a dying css, so it is up to the caller to use tryget logic
- * to confirm it is alive and well.
- */
-static inline struct cgroup_subsys_state *blkcg_css(void)
-{
-	struct cgroup_subsys_state *css;
-
-	css = kthread_blkcg();
-	if (css)
-		return css;
-	return task_css(current, io_cgrp_id);
-}
-
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
  * @return: true if this bio needs to be submitted with the root blkg context.
-- 
2.30.2

[PATCH 12/15] blk-cgroup: move blkcg_css to blk-cgroup.c

[Christoph Hellwig]

blkcg_css is only used in blk-cgroup.c, so move it there.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 block/blk-cgroup.c | 17 +++++++++++++++++
 block/blk-cgroup.h | 17 -----------------
 2 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8e32cc494808d..8da00ddc1766e 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -59,6 +59,23 @@ static struct workqueue_struct *blkcg_punt_bio_wq;
 
 #define BLKG_DESTROY_BATCH_SIZE  64
 
+/**
+ * blkcg_css - find the current css
+ *
+ * Find the css associated with either the kthread or the current task.
+ * This may return a dying css, so it is up to the caller to use tryget logic
+ * to confirm it is alive and well.
+ */
+static struct cgroup_subsys_state *blkcg_css(void)
+{
+	struct cgroup_subsys_state *css;
+
+	css = kthread_blkcg();
+	if (css)
+		return css;
+	return task_css(current, io_cgrp_id);
+}
+
 static bool blkcg_policy_enabled(struct request_queue *q,
 				 const struct blkcg_policy *pol)
 {
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 62ed8ed50b6e3..bb670e53a1de2 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -210,23 +210,6 @@ int blkg_conf_prep(struct blkcg *blkcg, const struct blkcg_policy *pol,
 		   char *input, struct blkg_conf_ctx *ctx);
 void blkg_conf_finish(struct blkg_conf_ctx *ctx);
 
-/**
- * blkcg_css - find the current css
- *
- * Find the css associated with either the kthread or the current task.
- * This may return a dying css, so it is up to the caller to use tryget logic
- * to confirm it is alive and well.
- */
-static inline struct cgroup_subsys_state *blkcg_css(void)
-{
-	struct cgroup_subsys_state *css;
-
-	css = kthread_blkcg();
-	if (css)
-		return css;
-	return task_css(current, io_cgrp_id);
-}
-
 /**
  * bio_issue_as_root_blkg - see if this bio needs to be issued as root blkg
  * @return: true if this bio needs to be submitted with the root blkg context.
-- 
2.30.2

[PATCH 13/15] blk-cgroup: cleanup blk_cgroup_congested

[Christoph Hellwig]

Use blkcg_css instead of open coding it, and switch to a slightly
more natural for loop.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 8da00ddc1766e..5684a8ce1f755 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -2038,15 +2038,11 @@ bool blk_cgroup_congested(void)
 	bool ret = false;
 
 	rcu_read_lock();
-	css = kthread_blkcg();
-	if (!css)
-		css = task_css(current, io_cgrp_id);
-	while (css) {
+	for (css = blkcg_css(); css; css = css->parent) {
 		if (atomic_read(&css->cgroup->congestion_count)) {
 			ret = true;
 			break;
 		}
-		css = css->parent;
 	}
 	rcu_read_unlock();
 	return ret;
-- 
2.30.2

[PATCH 14/15] blk-cgroup: cleanup blkcg_maybe_throttle_current

[Christoph Hellwig]

Use blkcg_css instead of opencoding it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 block/blk-cgroup.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 5684a8ce1f755..a91f8ae18b49b 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1808,7 +1808,6 @@ static void blkcg_maybe_throttle_blkg(struct blkcg_gq *blkg, bool use_memdelay)
 void blkcg_maybe_throttle_current(void)
 {
 	struct request_queue *q = current->throttle_queue;
-	struct cgroup_subsys_state *css;
 	struct blkcg *blkcg;
 	struct blkcg_gq *blkg;
 	bool use_memdelay = current->use_memdelay;
@@ -1820,12 +1819,7 @@ void blkcg_maybe_throttle_current(void)
 	current->use_memdelay = false;
 
 	rcu_read_lock();
-	css = kthread_blkcg();
-	if (css)
-		blkcg = css_to_blkcg(css);
-	else
-		blkcg = css_to_blkcg(task_css(current, io_cgrp_id));
-
+	blkcg = css_to_blkcg(blkcg_css());
 	if (!blkcg)
 		goto out;
 	blkg = blkg_lookup(blkcg, q);
-- 
2.30.2

[PATCH 15/15] kthread: unexport kthread_blkcg

[Christoph Hellwig]

kthread_blkcg is only used by the built-in blk-cgroup code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 include/linux/kthread.h | 4 ----
 kernel/kthread.c        | 1 -
 2 files changed, 5 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index de5d75bafd665..30e5bec81d2b6 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -222,9 +222,5 @@ void kthread_associate_blkcg(struct cgroup_subsys_state *css);
 struct cgroup_subsys_state *kthread_blkcg(void);
 #else
 static inline void kthread_associate_blkcg(struct cgroup_subsys_state *css) { }
-static inline struct cgroup_subsys_state *kthread_blkcg(void)
-{
-	return NULL;
-}
 #endif
 #endif /* _LINUX_KTHREAD_H */
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 50265f69a1354..544fd40974068 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -1522,5 +1522,4 @@ struct cgroup_subsys_state *kthread_blkcg(void)
 	}
 	return NULL;
 }
-EXPORT_SYMBOL(kthread_blkcg);
 #endif
-- 
2.30.2

[PATCH 15/15] kthread: unexport kthread_blkcg

[Christoph Hellwig]

kthread_blkcg is only used by the built-in blk-cgroup code.

Signed-off-by: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
---
 include/linux/kthread.h | 4 ----
 kernel/kthread.c        | 1 -
 2 files changed, 5 deletions(-)

diff --git a/include/linux/kthread.h b/include/linux/kthread.h
index de5d75bafd665..30e5bec81d2b6 100644
--- a/include/linux/kthread.h
+++ b/include/linux/kthread.h
@@ -222,9 +222,5 @@ void kthread_associate_blkcg(struct cgroup_subsys_state *css);
 struct cgroup_subsys_state *kthread_blkcg(void);
 #else
 static inline void kthread_associate_blkcg(struct cgroup_subsys_state *css) { }
-static inline struct cgroup_subsys_state *kthread_blkcg(void)
-{
-	return NULL;
-}
 #endif
 #endif /* _LINUX_KTHREAD_H */
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 50265f69a1354..544fd40974068 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -1522,5 +1522,4 @@ struct cgroup_subsys_state *kthread_blkcg(void)
 	}
 	return NULL;
 }
-EXPORT_SYMBOL(kthread_blkcg);
 #endif
-- 
2.30.2

Re: make the blkcg and blkcg structures private

[Tejun Heo]

Hello,

On Wed, Apr 20, 2022 at 06:27:08AM +0200, Christoph Hellwig wrote:
> this series cleans up various lose end in the blk-cgroup code to make it
> easier to follow in preparation of reworking the blkcg assignment for
> bios.  The biggest change is that most of <linux/blk-cgroup.h> is now
> taken private into block/.

The patches look all good to me and I'm not against making things more
private but can you elaborate on the rationale a bit more? By and large, we
have never been shy about putting things in the headers if there's *any*
(perceived) gain to be made from doing so, or even just as a way to pick the
locations for different things - type defs go on header and so on. Most of
the inlines and [un]likely's that we have are rather silly with modern
compilers with global optimizations, so it does make sense to get tidier,
but if that's the rationale, mentioning that in the commit message, even
briefly, would be great - ie. it should explain the benefits of adding these
few accessors to keep the definition private.

Thanks.

-- 
tejun

Re: make the blkcg and blkcg structures private

[Tejun Heo]

Hello,

On Wed, Apr 20, 2022 at 06:27:08AM +0200, Christoph Hellwig wrote:
> this series cleans up various lose end in the blk-cgroup code to make it
> easier to follow in preparation of reworking the blkcg assignment for
> bios.  The biggest change is that most of <linux/blk-cgroup.h> is now
> taken private into block/.

The patches look all good to me and I'm not against making things more
private but can you elaborate on the rationale a bit more? By and large, we
have never been shy about putting things in the headers if there's *any*
(perceived) gain to be made from doing so, or even just as a way to pick the
locations for different things - type defs go on header and so on. Most of
the inlines and [un]likely's that we have are rather silly with modern
compilers with global optimizations, so it does make sense to get tidier,
but if that's the rationale, mentioning that in the commit message, even
briefly, would be great - ie. it should explain the benefits of adding these
few accessors to keep the definition private.

Thanks.

-- 
tejun

Re: make the blkcg and blkcg structures private

[Christoph Hellwig]

On Thu, Apr 21, 2022 at 11:44:43AM -1000, Tejun Heo wrote:
> The patches look all good to me and I'm not against making things more
> private but can you elaborate on the rationale a bit more? By and large, we
> have never been shy about putting things in the headers if there's *any*
> (perceived) gain to be made from doing so, or even just as a way to pick the
> locations for different things - type defs go on header and so on. Most of
> the inlines and [un]likely's that we have are rather silly with modern
> compilers with global optimizations, so it does make sense to get tidier,
> but if that's the rationale, mentioning that in the commit message, even
> briefly, would be great - ie. it should explain the benefits of adding these
> few accessors to keep the definition private.

Mostly to help me understand the code :)  between all the moving to
and from the css struture it is a bit of a mess, and limiting the scope
that deals with the structures greatly helps with that.

Re: make the blkcg and blkcg structures private

[Christoph Hellwig]

On Thu, Apr 21, 2022 at 11:44:43AM -1000, Tejun Heo wrote:
> The patches look all good to me and I'm not against making things more
> private but can you elaborate on the rationale a bit more? By and large, we
> have never been shy about putting things in the headers if there's *any*
> (perceived) gain to be made from doing so, or even just as a way to pick the
> locations for different things - type defs go on header and so on. Most of
> the inlines and [un]likely's that we have are rather silly with modern
> compilers with global optimizations, so it does make sense to get tidier,
> but if that's the rationale, mentioning that in the commit message, even
> briefly, would be great - ie. it should explain the benefits of adding these
> few accessors to keep the definition private.

Mostly to help me understand the code :)  between all the moving to
and from the css struture it is a bit of a mess, and limiting the scope
that deals with the structures greatly helps with that.

Re: make the blkcg and blkcg structures private

[Tejun Heo]

Hello,

On Fri, Apr 22, 2022 at 06:23:18AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 21, 2022 at 11:44:43AM -1000, Tejun Heo wrote:
> > The patches look all good to me and I'm not against making things more
> > private but can you elaborate on the rationale a bit more? By and large, we
> > have never been shy about putting things in the headers if there's *any*
> > (perceived) gain to be made from doing so, or even just as a way to pick the
> > locations for different things - type defs go on header and so on. Most of
> > the inlines and [un]likely's that we have are rather silly with modern
> > compilers with global optimizations, so it does make sense to get tidier,
> > but if that's the rationale, mentioning that in the commit message, even
> > briefly, would be great - ie. it should explain the benefits of adding these
> > few accessors to keep the definition private.
> 
> Mostly to help me understand the code :)  between all the moving to
> and from the css struture it is a bit of a mess, and limiting the scope
> that deals with the structures greatly helps with that.

Hahaha, yeah, fair enough. I don't see a reason to not apply the patchset
given that the code is better organized and easier to follow afterewards.
For the series,

 Acked-by: Tejun Heo <tj@kernel.org>

Thanks.

-- 
tejun

Re: make the blkcg and blkcg structures private

[Tejun Heo]

Hello,

On Fri, Apr 22, 2022 at 06:23:18AM +0200, Christoph Hellwig wrote:
> On Thu, Apr 21, 2022 at 11:44:43AM -1000, Tejun Heo wrote:
> > The patches look all good to me and I'm not against making things more
> > private but can you elaborate on the rationale a bit more? By and large, we
> > have never been shy about putting things in the headers if there's *any*
> > (perceived) gain to be made from doing so, or even just as a way to pick the
> > locations for different things - type defs go on header and so on. Most of
> > the inlines and [un]likely's that we have are rather silly with modern
> > compilers with global optimizations, so it does make sense to get tidier,
> > but if that's the rationale, mentioning that in the commit message, even
> > briefly, would be great - ie. it should explain the benefits of adding these
> > few accessors to keep the definition private.
> 
> Mostly to help me understand the code :)  between all the moving to
> and from the css struture it is a bit of a mess, and limiting the scope
> that deals with the structures greatly helps with that.

Hahaha, yeah, fair enough. I don't see a reason to not apply the patchset
given that the code is better organized and easier to follow afterewards.
For the series,

 Acked-by: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>

Thanks.

-- 
tejun

Re: make the blkcg and blkcg structures private

[Christoph Hellwig]

ping?

Re: make the blkcg and blkcg structures private

[Christoph Hellwig]

ping?

Re: make the blkcg and blkcg structures private

[Jens Axboe]

On Wed, 20 Apr 2022 06:27:08 +0200, Christoph Hellwig wrote:
> this series cleans up various lose end in the blk-cgroup code to make it
> easier to follow in preparation of reworking the blkcg assignment for
> bios.  The biggest change is that most of <linux/blk-cgroup.h> is now
> taken private into block/.
> 
> Diffstat:
>  block/Makefile                |    1
>  block/bfq-iosched.h           |    4
>  block/blk-cgroup-fc-appid.c   |   57 +++++++++
>  block/blk-cgroup.c            |  154 ++++++++++++++++++++-----
>  block/blk-cgroup.h            |  138 +++++++++++++++-------
>  block/blk-throttle.c          |    2
>  drivers/block/loop.c          |   12 +
>  drivers/nvme/host/fc.c        |   26 +---
>  drivers/scsi/lpfc/lpfc_scsi.c |    4
>  include/linux/backing-dev.h   |    6
>  include/linux/blk-cgroup.h    |  258 ++----------------------------------------
>  include/linux/blktrace_api.h  |   10 -
>  include/linux/kthread.h       |    4
>  kernel/kthread.c              |    1
>  kernel/trace/blktrace.c       |   26 ++--
>  mm/backing-dev.c              |   19 +--
>  mm/readahead.c                |    1
>  mm/swapfile.c                 |    1
>  18 files changed, 343 insertions(+), 381 deletions(-)
> 
> [...]

Applied, thanks!

[01/15] blk-cgroup: remove __bio_blkcg
        commit: 2524a5783e7d49e7cd936f582485a2bb4567edd1
[02/15] nvme-fc: don't support the appid attribute without CONFIG_BLK_CGROUP_FC_APPID
        commit: 55d7baa371ad90d297daf4250720af77449fdec0
[03/15] nvme-fc: fold t fc_update_appid into fc_appid_store
        commit: c814153c83a892dfd42026eaa661ae2c1f298792
[04/15] blk-cgroup: move blkcg_{get,set}_fc_appid out of line
        commit: db05628435aa761d30b4eae481a82befe7a8492a
[05/15] blk-cgroup: move blk_cgroup_congested out line
        commit: 216889aad362b5b7e998a5371348b5e95d485dd1
[06/15] blk-cgroup: move blkcg_{pin,unpin}_online out of line
        commit: 397c9f46ee4d99024c64954b007c1b5762d01cb4
[07/15] blk-cgroup: move struct blkcg to block/blk-cgroup.h
        commit: dec223c92a4688f6c9642d640cfe15a99d289dd4
[08/15] blktrace: cleanup the __trace_note_message interface
        commit: f4a6a61cb6d40d9ae63e47743d33200f3efe3fe7
[09/15] blk-cgroup: replace bio_blkcg with bio_blkcg_css
        commit: bbb1ebe7a909db4de49777fb7676d5bf293f34c9
[10/15] blk-cgroup: remove pointless CONFIG_BLOCK ifdefs
        commit: 7f20ba7c42fd899557cef7d001f48711c3066ba5
[11/15] blk-cgroup: remove unneeded includes from <linux/blk-cgroup.h>
        commit: c97ab271576dec2170e7b804cb05f7617b30fed9
[12/15] blk-cgroup: move blkcg_css to blk-cgroup.c
        commit: bc5fee91f26d8d1428fb744e5ad04b1417a85197
[13/15] blk-cgroup: cleanup blk_cgroup_congested
        commit: d200ca143ac6d0b4391b4e811e67e1a36461d501
[14/15] blk-cgroup: cleanup blkcg_maybe_throttle_current
        commit: 82778259eb201870d6d4f95ca4162de60a682343
[15/15] kthread: unexport kthread_blkcg
        commit: f624506f98b198e65b44da303f44974590fb16c0

Best regards,
-- 
Jens Axboe