dax_supported() related cleanups v2

dax_supported() related cleanups v2

[Christoph Hellwig]

Hi all,

this series first clarifies how to use fsdax in the Kconfig help a bit,
and then untangles the code path that checks if fsdax is supported.

Changes since v1:
 - improve the FS_DAX Kconfig help text further
 - write a proper commit log for a patch missing it

Diffstat
 drivers/dax/super.c   |  191 +++++++++++++++++++-------------------------------
 drivers/md/dm-table.c |    9 --
 drivers/md/dm.c       |    2 
 fs/Kconfig            |   21 ++++-
 fs/ext2/super.c       |    3 
 fs/ext4/super.c       |    3 
 fs/xfs/xfs_super.c    |   16 +++-
 include/linux/dax.h   |   41 +---------
 8 files changed, 117 insertions(+), 169 deletions(-)

[PATCH 1/3] nvdimm/pmem: fix creating the dax group

[Christoph Hellwig]

The recent block layer refactoring broke the way how the pmem driver
abused device_add_disk.  Fix this by properly passing the attribute groups
to device_add_disk.

Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/nvdimm/pmem.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 72de88ff0d30d..ef4950f808326 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -380,7 +380,6 @@ static int pmem_attach_disk(struct device *dev,
 	struct nd_pfn_sb *pfn_sb;
 	struct pmem_device *pmem;
 	struct request_queue *q;
-	struct device *gendev;
 	struct gendisk *disk;
 	void *addr;
 	int rc;
@@ -489,10 +488,8 @@ static int pmem_attach_disk(struct device *dev,
 	}
 	dax_write_cache(dax_dev, nvdimm_has_cache(nd_region));
 	pmem->dax_dev = dax_dev;
-	gendev = disk_to_dev(disk);
-	gendev->groups = pmem_attribute_groups;
 
-	device_add_disk(dev, disk, NULL);
+	device_add_disk(dev, disk, pmem_attribute_groups);
 	if (devm_add_action_or_reset(dev, pmem_release_disk, pmem))
 		return -ENOMEM;
 
-- 
2.30.2

[PATCH 2/3] nvdimm/pmem: move dax_attribute_group from dax to pmem

[Christoph Hellwig]

dax_attribute_group is only used by the pmem driver, and can avoid the
completely pointless lookup by the disk name if moved there.  This
leaves just a single caller of dax_get_by_host, so move dax_get_by_host
into the same ifdef block as that caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/dax/super.c   | 100 ++++++++----------------------------------
 drivers/nvdimm/pmem.c |  43 ++++++++++++++++++
 include/linux/dax.h   |   2 -
 3 files changed, 61 insertions(+), 84 deletions(-)

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index fc89e91beea7c..b882cf8106ea3 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -63,6 +63,24 @@ static int dax_host_hash(const char *host)
 	return hashlen_hash(hashlen_string("DAX", host)) % DAX_HASH_SIZE;
 }
 
+#ifdef CONFIG_BLOCK
+#include <linux/blkdev.h>
+
+int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
+		pgoff_t *pgoff)
+{
+	sector_t start_sect = bdev ? get_start_sect(bdev) : 0;
+	phys_addr_t phys_off = (start_sect + sector) * 512;
+
+	if (pgoff)
+		*pgoff = PHYS_PFN(phys_off);
+	if (phys_off % PAGE_SIZE || size % PAGE_SIZE)
+		return -EINVAL;
+	return 0;
+}
+EXPORT_SYMBOL(bdev_dax_pgoff);
+
+#if IS_ENABLED(CONFIG_FS_DAX)
 /**
  * dax_get_by_host() - temporary lookup mechanism for filesystem-dax
  * @host: alternate name for the device registered by a dax driver
@@ -94,24 +112,6 @@ static struct dax_device *dax_get_by_host(const char *host)
 	return found;
 }
 
-#ifdef CONFIG_BLOCK
-#include <linux/blkdev.h>
-
-int bdev_dax_pgoff(struct block_device *bdev, sector_t sector, size_t size,
-		pgoff_t *pgoff)
-{
-	sector_t start_sect = bdev ? get_start_sect(bdev) : 0;
-	phys_addr_t phys_off = (start_sect + sector) * 512;
-
-	if (pgoff)
-		*pgoff = PHYS_PFN(phys_off);
-	if (phys_off % PAGE_SIZE || size % PAGE_SIZE)
-		return -EINVAL;
-	return 0;
-}
-EXPORT_SYMBOL(bdev_dax_pgoff);
-
-#if IS_ENABLED(CONFIG_FS_DAX)
 struct dax_device *fs_dax_get_by_bdev(struct block_device *bdev)
 {
 	if (!blk_queue_dax(bdev->bd_disk->queue))
@@ -231,70 +231,6 @@ enum dax_device_flags {
 	DAXDEV_SYNC,
 };
 
-static ssize_t write_cache_show(struct device *dev,
-		struct device_attribute *attr, char *buf)
-{
-	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
-	ssize_t rc;
-
-	WARN_ON_ONCE(!dax_dev);
-	if (!dax_dev)
-		return -ENXIO;
-
-	rc = sprintf(buf, "%d\n", !!dax_write_cache_enabled(dax_dev));
-	put_dax(dax_dev);
-	return rc;
-}
-
-static ssize_t write_cache_store(struct device *dev,
-		struct device_attribute *attr, const char *buf, size_t len)
-{
-	bool write_cache;
-	int rc = strtobool(buf, &write_cache);
-	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
-
-	WARN_ON_ONCE(!dax_dev);
-	if (!dax_dev)
-		return -ENXIO;
-
-	if (rc)
-		len = rc;
-	else
-		dax_write_cache(dax_dev, write_cache);
-
-	put_dax(dax_dev);
-	return len;
-}
-static DEVICE_ATTR_RW(write_cache);
-
-static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n)
-{
-	struct device *dev = container_of(kobj, typeof(*dev), kobj);
-	struct dax_device *dax_dev = dax_get_by_host(dev_name(dev));
-
-	WARN_ON_ONCE(!dax_dev);
-	if (!dax_dev)
-		return 0;
-
-#ifndef CONFIG_ARCH_HAS_PMEM_API
-	if (a == &dev_attr_write_cache.attr)
-		return 0;
-#endif
-	return a->mode;
-}
-
-static struct attribute *dax_attributes[] = {
-	&dev_attr_write_cache.attr,
-	NULL,
-};
-
-struct attribute_group dax_attribute_group = {
-	.name = "dax",
-	.attrs = dax_attributes,
-	.is_visible = dax_visible,
-};
-EXPORT_SYMBOL_GPL(dax_attribute_group);
-
 /**
  * dax_direct_access() - translate a device pgoff to an absolute pfn
  * @dax_dev: a dax_device instance representing the logical memory range
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index ef4950f808326..bbeb3f46db157 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -328,6 +328,49 @@ static const struct dax_operations pmem_dax_ops = {
 	.zero_page_range = pmem_dax_zero_page_range,
 };
 
+static ssize_t write_cache_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct pmem_device *pmem = dev_to_disk(dev)->private_data;
+
+	return sprintf(buf, "%d\n", !!dax_write_cache_enabled(pmem->dax_dev));
+}
+
+static ssize_t write_cache_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t len)
+{
+	struct pmem_device *pmem = dev_to_disk(dev)->private_data;
+	bool write_cache;
+	int rc;
+
+	rc = strtobool(buf, &write_cache);
+	if (rc)
+		return rc;
+	dax_write_cache(pmem->dax_dev, write_cache);
+	return len;
+}
+static DEVICE_ATTR_RW(write_cache);
+
+static umode_t dax_visible(struct kobject *kobj, struct attribute *a, int n)
+{
+#ifndef CONFIG_ARCH_HAS_PMEM_API
+	if (a == &dev_attr_write_cache.attr)
+		return 0;
+#endif
+	return a->mode;
+}
+
+static struct attribute *dax_attributes[] = {
+	&dev_attr_write_cache.attr,
+	NULL,
+};
+
+static const struct attribute_group dax_attribute_group = {
+	.name		= "dax",
+	.attrs		= dax_attributes,
+	.is_visible	= dax_visible,
+};
+
 static const struct attribute_group *pmem_attribute_groups[] = {
 	&dax_attribute_group,
 	NULL,
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 2619d94c308d4..8623caa673889 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -38,8 +38,6 @@ struct dax_operations {
 	int (*zero_page_range)(struct dax_device *, pgoff_t, size_t);
 };
 
-extern struct attribute_group dax_attribute_group;
-
 #if IS_ENABLED(CONFIG_DAX)
 struct dax_device *alloc_dax(void *private, const char *host,
 		const struct dax_operations *ops, unsigned long flags);
-- 
2.30.2

[PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Christoph Hellwig]

The proper API is to pass the groups to device_add_disk, but the code
used to also allow groups being set before calling *add_disk.  Warn
about that but keep the group pointer intact for now so that it can
be removed again after a grace period.

Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
---
 block/genhd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 7b6e5e1cf9564..409cf608cc5bd 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -439,7 +439,8 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
 	dev_set_uevent_suppress(ddev, 1);
 
 	ddev->parent = parent;
-	ddev->groups = groups;
+	if (!WARN_ON_ONCE(ddev->groups))
+		ddev->groups = groups;
 	dev_set_name(ddev, "%s", disk->disk_name);
 	if (!(disk->flags & GENHD_FL_HIDDEN))
 		ddev->devt = MKDEV(disk->major, disk->first_minor);
-- 
2.30.2

Re: dax_supported() related cleanups v2

[Dan Williams]

On Wed, Sep 22, 2021 at 10:37 AM Christoph Hellwig <hch@lst.de> wrote:
>
> Hi all,
>
> this series first clarifies how to use fsdax in the Kconfig help a bit,
> and then untangles the code path that checks if fsdax is supported.
>
> Changes since v1:
>  - improve the FS_DAX Kconfig help text further
>  - write a proper commit log for a patch missing it
>

This looks like your send script picked up the wrong cover letter?

> Diffstat
>  drivers/dax/super.c   |  191 +++++++++++++++++++-------------------------------
>  drivers/md/dm-table.c |    9 --
>  drivers/md/dm.c       |    2
>  fs/Kconfig            |   21 ++++-
>  fs/ext2/super.c       |    3
>  fs/ext4/super.c       |    3
>  fs/xfs/xfs_super.c    |   16 +++-
>  include/linux/dax.h   |   41 +---------
>  8 files changed, 117 insertions(+), 169 deletions(-)

Re: dax_supported() related cleanups v2

[Christoph Hellwig]

On Wed, Sep 22, 2021 at 10:55:01AM -0700, Dan Williams wrote:
> This looks like your send script picked up the wrong cover letter?

Yes.  Or the human running the script to be exact :)

fix a dax/block device attribute registration regression

[Christoph Hellwig]

Hi Dan and Jens,

this series fixed a regression in how the dax/write_cache attribute of the
pmem devices was registere.  It does so by both fixing the API abuse in the
driver and (temporarily) the behavior change in the block layer that made
this API abuse not work anymore.

Diffstat:
 block/genhd.c         |    3 +-
 drivers/dax/super.c   |   64 --------------------------------------------------
 drivers/nvdimm/pmem.c |   48 ++++++++++++++++++++++++++++++++++---
 include/linux/dax.h   |    2 -
 4 files changed, 46 insertions(+), 71 deletions(-)

[PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Christoph Hellwig]

The proper API is to pass the groups to device_add_disk, but the code
used to also allow groups being set before calling *add_disk.  Warn
about that but keep the group pointer intact for now so that it can
be removed again after a grace period.

Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
---
 block/genhd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 7b6e5e1cf9564..409cf608cc5bd 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -439,7 +439,8 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
 	dev_set_uevent_suppress(ddev, 1);
 
 	ddev->parent = parent;
-	ddev->groups = groups;
+	if (!WARN_ON_ONCE(ddev->groups))
+		ddev->groups = groups;
 	dev_set_name(ddev, "%s", disk->disk_name);
 	if (!(disk->flags & GENHD_FL_HIDDEN))
 		ddev->devt = MKDEV(disk->major, disk->first_minor);
-- 
2.30.2

fix a dax/block device attribute registration regression

[Christoph Hellwig]

Hi Dan and Jens,

this series fixed a regression in how the dax/write_cache attribute of the
pmem devices was registere.  It does so by both fixing the API abuse in the
driver and (temporarily) the behavior change in the block layer that made
this API abuse not work anymore.

Diffstat:
 block/genhd.c         |    3 +-
 drivers/dax/super.c   |   64 --------------------------------------------------
 drivers/nvdimm/pmem.c |   48 ++++++++++++++++++++++++++++++++++---
 include/linux/dax.h   |    2 -
 4 files changed, 46 insertions(+), 71 deletions(-)

[PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Christoph Hellwig]

The proper API is to pass the groups to device_add_disk, but the code
used to also allow groups being set before calling *add_disk.  Warn
about that but keep the group pointer intact for now so that it can
be removed again after a grace period.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")
---
 block/genhd.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/genhd.c b/block/genhd.c
index 7b6e5e1cf9564..409cf608cc5bd 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -439,7 +439,8 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
 	dev_set_uevent_suppress(ddev, 1);
 
 	ddev->parent = parent;
-	ddev->groups = groups;
+	if (!WARN_ON_ONCE(ddev->groups))
+		ddev->groups = groups;
 	dev_set_name(ddev, "%s", disk->disk_name);
 	if (!(disk->flags & GENHD_FL_HIDDEN))
 		ddev->devt = MKDEV(disk->major, disk->first_minor);
-- 
2.30.2

Re: [PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Ira Weiny]

On Mon, Sep 20, 2021 at 09:27:26AM +0200, Christoph Hellwig wrote:
> The proper API is to pass the groups to device_add_disk, but the code
> used to also allow groups being set before calling *add_disk.  Warn
> about that but keep the group pointer intact for now so that it can
> be removed again after a grace period.
> 
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")

Reviewed-by: Ira Weiny <ira.weiny@intel.com>

> ---
>  block/genhd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/block/genhd.c b/block/genhd.c
> index 7b6e5e1cf9564..409cf608cc5bd 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -439,7 +439,8 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
>  	dev_set_uevent_suppress(ddev, 1);
>  
>  	ddev->parent = parent;
> -	ddev->groups = groups;
> +	if (!WARN_ON_ONCE(ddev->groups))
> +		ddev->groups = groups;
>  	dev_set_name(ddev, "%s", disk->disk_name);
>  	if (!(disk->flags & GENHD_FL_HIDDEN))
>  		ddev->devt = MKDEV(disk->major, disk->first_minor);
> -- 
> 2.30.2
> 

Re: [PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Dan Williams]

On Mon, Sep 20, 2021 at 12:30 AM Christoph Hellwig <hch@lst.de> wrote:
>
> The proper API is to pass the groups to device_add_disk, but the code
> used to also allow groups being set before calling *add_disk.  Warn
> about that but keep the group pointer intact for now so that it can
> be removed again after a grace period.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>
> Fixes: 52b85909f85d ("block: fold register_disk into device_add_disk")
> ---
>  block/genhd.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 7b6e5e1cf9564..409cf608cc5bd 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -439,7 +439,8 @@ int device_add_disk(struct device *parent, struct gendisk *disk,
>         dev_set_uevent_suppress(ddev, 1);
>
>         ddev->parent = parent;
> -       ddev->groups = groups;
> +       if (!WARN_ON_ONCE(ddev->groups))
> +               ddev->groups = groups;

That feels too compact to me, and dev_WARN_ONCE() might save someone a
git blame to look up the reason for the warning:

    dev_WARN_ONCE(parent, ddev->groups, "unexpected pre-populated
attribute group\n");
    if (!ddev->groups)
        ddev->groups = groups;

...but not a deal breaker. Either way you can add:

Reviewed-by: Dan Williams <dan.j.williams@intel.com>

Jens, I'm ok for the final spin of this series to go through block.git
since the referenced commits in Fixes: went that route, just let me
know if you want me to take them.

Re: [PATCH 3/3] block: warn if ->groups is set when calling add_disk

[Christoph Hellwig]

On Mon, Sep 20, 2021 at 04:50:03PM -0700, Dan Williams wrote:
> >
> >         ddev->parent = parent;
> > -       ddev->groups = groups;
> > +       if (!WARN_ON_ONCE(ddev->groups))
> > +               ddev->groups = groups;
> 
> That feels too compact to me, and dev_WARN_ONCE() might save someone a
> git blame to look up the reason for the warning:
> 
>     dev_WARN_ONCE(parent, ddev->groups, "unexpected pre-populated
> attribute group\n");
>     if (!ddev->groups)
>         ddev->groups = groups;
> 
> ...but not a deal breaker. Either way you can add:
> 

I'd rather keep it simple and optmize for the normal case..