[PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

[PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

[Sean Nyekjaer]

Follow-up on discussion in:
https://lkml.org/lkml/2021/10/4/41
https://lkml.org/lkml/2021/10/11/435

Changes since v3:
 - edited commit msg and author for mtdconcat patch

Changes since v2:
 - added signoff's to patch from Boris
 - removed accidential line break
 - kept tests consistent: master->master.suspended == 0 -> !master->master.suspended
 - added comments to mtdconcat patch
 - moved mtdconcat before ('mtd: core: protect access to MTD devices while in suspend')

Changes since v1:
 - removed __mtd_suspend/__mtd_resume functions as they are not used by
   mtdconcat anymore.
 - only master mtd_info is used for mtd_{start,end}_access(). Warn if we
   got mtd's.
 - added Boris patch for using uninitialized _suspend/_resume hooks when
   bbt scanning
 - mtdconcat uses device _suspend/_resume hooks
 - I don't really like the macro proposal from Boris
   mtd_no_suspend_void_call()/mtd_no_suspend_ret_call() I think they
   make the code complex to read and the macro's doesn't fit every
   where anyway...

Changes since from rfc v1/v2:
 - added access protection for all device access hooks in mtd_info.
 - added Suggested-by to [1/3] patch.
 - removed refereces to commit ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
   from commit msg as commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") is 
   to be blamed.
 - tested on a kernel with LOCKDEP enabled.

Boris Brezillon (2):
  mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt
  mtd: mtdconcat: don't use mtd_{suspend,resume}()

Sean Nyekjaer (2):
  mtd: core: protect access to MTD devices while in suspend
  mtd: rawnand: remove suspended check

 drivers/mtd/mtdconcat.c          |  15 +++-
 drivers/mtd/mtdcore.c            | 124 +++++++++++++++++++++++++++----
 drivers/mtd/nand/raw/nand_base.c |  52 ++++---------
 drivers/mtd/nand/raw/nand_bbt.c  |  28 ++++++-
 include/linux/mtd/mtd.h          |  81 ++++++++++++++++----
 include/linux/mtd/rawnand.h      |   5 +-
 6 files changed, 230 insertions(+), 75 deletions(-)

-- 
2.33.0

[PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

[Sean Nyekjaer]

Follow-up on discussion in:
https://lkml.org/lkml/2021/10/4/41
https://lkml.org/lkml/2021/10/11/435

Changes since v3:
 - edited commit msg and author for mtdconcat patch

Changes since v2:
 - added signoff's to patch from Boris
 - removed accidential line break
 - kept tests consistent: master->master.suspended == 0 -> !master->master.suspended
 - added comments to mtdconcat patch
 - moved mtdconcat before ('mtd: core: protect access to MTD devices while in suspend')

Changes since v1:
 - removed __mtd_suspend/__mtd_resume functions as they are not used by
   mtdconcat anymore.
 - only master mtd_info is used for mtd_{start,end}_access(). Warn if we
   got mtd's.
 - added Boris patch for using uninitialized _suspend/_resume hooks when
   bbt scanning
 - mtdconcat uses device _suspend/_resume hooks
 - I don't really like the macro proposal from Boris
   mtd_no_suspend_void_call()/mtd_no_suspend_ret_call() I think they
   make the code complex to read and the macro's doesn't fit every
   where anyway...

Changes since from rfc v1/v2:
 - added access protection for all device access hooks in mtd_info.
 - added Suggested-by to [1/3] patch.
 - removed refereces to commit ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
   from commit msg as commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") is 
   to be blamed.
 - tested on a kernel with LOCKDEP enabled.

Boris Brezillon (2):
  mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt
  mtd: mtdconcat: don't use mtd_{suspend,resume}()

Sean Nyekjaer (2):
  mtd: core: protect access to MTD devices while in suspend
  mtd: rawnand: remove suspended check

 drivers/mtd/mtdconcat.c          |  15 +++-
 drivers/mtd/mtdcore.c            | 124 +++++++++++++++++++++++++++----
 drivers/mtd/nand/raw/nand_base.c |  52 ++++---------
 drivers/mtd/nand/raw/nand_bbt.c  |  28 ++++++-
 include/linux/mtd/mtd.h          |  81 ++++++++++++++++----
 include/linux/mtd/rawnand.h      |   5 +-
 6 files changed, 230 insertions(+), 75 deletions(-)

-- 
2.33.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Sean Nyekjaer]

From: Boris Brezillon <boris.brezillon@collabora.com>

The BBT scan logic use the MTD helpers before the MTD layer had a
chance to initialize the device, and that leads to issues when
accessing the uninitialized suspend lock. Let's temporarily set the
suspend/resume hooks to NULL to skip the lock acquire/release step.

Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/nand/raw/nand_bbt.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
index b7ad030225f8..93d385703469 100644
--- a/drivers/mtd/nand/raw/nand_bbt.c
+++ b/drivers/mtd/nand/raw/nand_bbt.c
@@ -1397,8 +1397,28 @@ static int nand_create_badblock_pattern(struct nand_chip *this)
  */
 int nand_create_bbt(struct nand_chip *this)
 {
+	struct mtd_info *mtd = nand_to_mtd(this);
+	int (*suspend) (struct mtd_info *) = mtd->_suspend;
+	void (*resume) (struct mtd_info *) = mtd->_resume;
 	int ret;
 
+	/*
+	 * The BBT scan logic use the MTD helpers before the MTD layer had a
+	 * chance to initialize the device, and that leads to issues when
+	 * accessing the uninitialized suspend lock. Let's temporarily set the
+	 * suspend/resume hooks to NULL to skip the lock acquire/release step.
+	 *
+	 * FIXME: This is an ugly hack, so please don't copy this pattern to
+	 * other MTD implementations. The proper fix would be to implement a
+	 * generic BBT scan logic at the NAND level that's not using any of the
+	 * MTD helpers to access pages. We also might consider doing a two
+	 * step initialization at the MTD level (mtd_device_init() +
+	 * mtd_device_register()) so some of the fields are initialized
+	 * early.
+	 */
+	mtd->_suspend = NULL;
+	mtd->_resume = NULL;
+
 	/* Is a flash based bad block table requested? */
 	if (this->bbt_options & NAND_BBT_USE_FLASH) {
 		/* Use the default pattern descriptors */
@@ -1422,7 +1442,13 @@ int nand_create_bbt(struct nand_chip *this)
 			return ret;
 	}
 
-	return nand_scan_bbt(this, this->badblock_pattern);
+	ret = nand_scan_bbt(this, this->badblock_pattern);
+
+	/* Restore the suspend/resume hooks. */
+	mtd->_suspend = suspend;
+	mtd->_resume = resume;
+
+	return ret;
 }
 EXPORT_SYMBOL(nand_create_bbt);
 
-- 
2.33.0

[PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Sean Nyekjaer]

From: Boris Brezillon <boris.brezillon@collabora.com>

The BBT scan logic use the MTD helpers before the MTD layer had a
chance to initialize the device, and that leads to issues when
accessing the uninitialized suspend lock. Let's temporarily set the
suspend/resume hooks to NULL to skip the lock acquire/release step.

Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/nand/raw/nand_bbt.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
index b7ad030225f8..93d385703469 100644
--- a/drivers/mtd/nand/raw/nand_bbt.c
+++ b/drivers/mtd/nand/raw/nand_bbt.c
@@ -1397,8 +1397,28 @@ static int nand_create_badblock_pattern(struct nand_chip *this)
  */
 int nand_create_bbt(struct nand_chip *this)
 {
+	struct mtd_info *mtd = nand_to_mtd(this);
+	int (*suspend) (struct mtd_info *) = mtd->_suspend;
+	void (*resume) (struct mtd_info *) = mtd->_resume;
 	int ret;
 
+	/*
+	 * The BBT scan logic use the MTD helpers before the MTD layer had a
+	 * chance to initialize the device, and that leads to issues when
+	 * accessing the uninitialized suspend lock. Let's temporarily set the
+	 * suspend/resume hooks to NULL to skip the lock acquire/release step.
+	 *
+	 * FIXME: This is an ugly hack, so please don't copy this pattern to
+	 * other MTD implementations. The proper fix would be to implement a
+	 * generic BBT scan logic at the NAND level that's not using any of the
+	 * MTD helpers to access pages. We also might consider doing a two
+	 * step initialization at the MTD level (mtd_device_init() +
+	 * mtd_device_register()) so some of the fields are initialized
+	 * early.
+	 */
+	mtd->_suspend = NULL;
+	mtd->_resume = NULL;
+
 	/* Is a flash based bad block table requested? */
 	if (this->bbt_options & NAND_BBT_USE_FLASH) {
 		/* Use the default pattern descriptors */
@@ -1422,7 +1442,13 @@ int nand_create_bbt(struct nand_chip *this)
 			return ret;
 	}
 
-	return nand_scan_bbt(this, this->badblock_pattern);
+	ret = nand_scan_bbt(this, this->badblock_pattern);
+
+	/* Restore the suspend/resume hooks. */
+	mtd->_suspend = suspend;
+	mtd->_resume = resume;
+
+	return ret;
 }
 EXPORT_SYMBOL(nand_create_bbt);
 
-- 
2.33.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 2/4] mtd: mtdconcat: don't use mtd_{suspend,resume}()

[Sean Nyekjaer]

From: Boris Brezillon <boris.brezillon@collabora.com>

The MTD suspend logic will soon be adjusted to automatically wait for
device wake-up before issuing IOs. In order to do that a new read-write
lock will be added and taken in write-mode in the
mtd_{suspend,resume}() path. Since mtdconcat.c itself is an MTD device,
calling mtd_suspend/resume() on subdevices from the mtdconcat
->_{suspend,resume}() hook will lead to a nested lock, which lockdep
will complain about if we don't add a proper annotation. Let's keep
things simple and replace those mtd_{suspend,resume}(subdev) calls by
subdev->_{suspend,resume}() ones to avoid this situation.

Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/mtdconcat.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index f685a581df48..f4a4274489b4 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -566,9 +566,15 @@ static int concat_suspend(struct mtd_info *mtd)
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
-		if ((rc = mtd_suspend(subdev)) < 0)
+		/*
+		 * Call the MTD hook directly to avoid a nested lock
+		 * on ->suspend_lock.
+		 */
+		rc = subdev->_suspend ? subdev->_suspend(subdev) : 0;
+		if (rc < 0)
 			return rc;
 	}
+
 	return rc;
 }
 
@@ -579,7 +585,12 @@ static void concat_resume(struct mtd_info *mtd)
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
-		mtd_resume(subdev);
+		/*
+		 * Call the MTD hook directly to avoid a nested lock
+		 * on ->resume_lock.
+		 */
+		if (subdev->_resume)
+			subdev->_resume(subdev);
 	}
 }
 
-- 
2.33.0

[PATCH v4 2/4] mtd: mtdconcat: don't use mtd_{suspend,resume}()

[Sean Nyekjaer]

From: Boris Brezillon <boris.brezillon@collabora.com>

The MTD suspend logic will soon be adjusted to automatically wait for
device wake-up before issuing IOs. In order to do that a new read-write
lock will be added and taken in write-mode in the
mtd_{suspend,resume}() path. Since mtdconcat.c itself is an MTD device,
calling mtd_suspend/resume() on subdevices from the mtdconcat
->_{suspend,resume}() hook will lead to a nested lock, which lockdep
will complain about if we don't add a proper annotation. Let's keep
things simple and replace those mtd_{suspend,resume}(subdev) calls by
subdev->_{suspend,resume}() ones to avoid this situation.

Tested-by: Sean Nyekjaer <sean@geanix.com>
Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/mtdconcat.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/mtd/mtdconcat.c b/drivers/mtd/mtdconcat.c
index f685a581df48..f4a4274489b4 100644
--- a/drivers/mtd/mtdconcat.c
+++ b/drivers/mtd/mtdconcat.c
@@ -566,9 +566,15 @@ static int concat_suspend(struct mtd_info *mtd)
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
-		if ((rc = mtd_suspend(subdev)) < 0)
+		/*
+		 * Call the MTD hook directly to avoid a nested lock
+		 * on ->suspend_lock.
+		 */
+		rc = subdev->_suspend ? subdev->_suspend(subdev) : 0;
+		if (rc < 0)
 			return rc;
 	}
+
 	return rc;
 }
 
@@ -579,7 +585,12 @@ static void concat_resume(struct mtd_info *mtd)
 
 	for (i = 0; i < concat->num_subdev; i++) {
 		struct mtd_info *subdev = concat->subdev[i];
-		mtd_resume(subdev);
+		/*
+		 * Call the MTD hook directly to avoid a nested lock
+		 * on ->resume_lock.
+		 */
+		if (subdev->_resume)
+			subdev->_resume(subdev);
 	}
 }
 
-- 
2.33.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 3/4] mtd: core: protect access to MTD devices while in suspend

[Sean Nyekjaer]

Prevent MTD access while in a suspended state. Also
prevent suspending a device which is still currently in use.

Commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") allows the
rawnand layer to return errors rather than waiting in a blocking wait.

Tested on a iMX6ULL.

Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/mtdcore.c   | 124 +++++++++++++++++++++++++++++++++++-----
 include/linux/mtd/mtd.h |  81 +++++++++++++++++++++-----
 2 files changed, 176 insertions(+), 29 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 153229198947..8e6b7e858ada 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -777,6 +777,8 @@ static void mtd_set_dev_defaults(struct mtd_info *mtd)
 	INIT_LIST_HEAD(&mtd->partitions);
 	mutex_init(&mtd->master.partitions_lock);
 	mutex_init(&mtd->master.chrdev_lock);
+	init_waitqueue_head(&mtd->master.resume_wq);
+	init_rwsem(&mtd->master.suspend_lock);
 }
 
 static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
@@ -1267,7 +1269,9 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
 
 	adjinstr.addr += mst_ofs;
 
+	mtd_start_access(master);
 	ret = master->_erase(master, &adjinstr);
+	mtd_end_access(master);
 
 	if (adjinstr.fail_addr != MTD_FAIL_ADDR_UNKNOWN) {
 		instr->fail_addr = adjinstr.fail_addr - mst_ofs;
@@ -1289,6 +1293,7 @@ int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	      void **virt, resource_size_t *phys)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	*virt = NULL;
@@ -1301,8 +1306,12 @@ int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	if (!len)
 		return 0;
 
+	mtd_start_access(master);
 	from = mtd_get_master_ofs(mtd, from);
-	return master->_point(master, from, len, retlen, virt, phys);
+	ret = master->_point(master, from, len, retlen, virt, phys);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_point);
 
@@ -1310,6 +1319,7 @@ EXPORT_SYMBOL_GPL(mtd_point);
 int mtd_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_unpoint)
 		return -EOPNOTSUPP;
@@ -1317,7 +1327,12 @@ int mtd_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 		return -EINVAL;
 	if (!len)
 		return 0;
-	return master->_unpoint(master, mtd_get_master_ofs(mtd, from), len);
+
+	mtd_start_access(master);
+	ret =  master->_unpoint(master, mtd_get_master_ofs(mtd, from), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_unpoint);
 
@@ -1372,6 +1387,7 @@ int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	};
 	int ret;
 
+	/* mtd_read_oob_std handles mtd access protection */
 	ret = mtd_read_oob(mtd, from, &ops);
 	*retlen = ops.retlen;
 
@@ -1388,6 +1404,7 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	};
 	int ret;
 
+	/* mtd_write_oob_std handles mtd access protection */
 	ret = mtd_write_oob(mtd, to, &ops);
 	*retlen = ops.retlen;
 
@@ -1406,6 +1423,7 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 		    const u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_panic_write)
@@ -1419,8 +1437,12 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	if (!master->oops_panic_write)
 		master->oops_panic_write = true;
 
-	return master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
-				    retlen, buf);
+	mtd_start_access(master);
+	ret = master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
+				   retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_panic_write);
 
@@ -1464,11 +1486,13 @@ static int mtd_read_oob_std(struct mtd_info *mtd, loff_t from,
 	int ret;
 
 	from = mtd_get_master_ofs(mtd, from);
+	mtd_start_access(master);
 	if (master->_read_oob)
 		ret = master->_read_oob(master, from, ops);
 	else
 		ret = master->_read(master, from, ops->len, &ops->retlen,
 				    ops->datbuf);
+	mtd_end_access(master);
 
 	return ret;
 }
@@ -1480,11 +1504,13 @@ static int mtd_write_oob_std(struct mtd_info *mtd, loff_t to,
 	int ret;
 
 	to = mtd_get_master_ofs(mtd, to);
+	mtd_start_access(master);
 	if (master->_write_oob)
 		ret = master->_write_oob(master, to, ops);
 	else
 		ret = master->_write(master, to, ops->len, &ops->retlen,
 				     ops->datbuf);
+	mtd_end_access(master);
 
 	return ret;
 }
@@ -1992,12 +2018,18 @@ int mtd_get_fact_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
 			   struct otp_info *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_get_fact_prot_info)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_get_fact_prot_info(master, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_get_fact_prot_info(master, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_get_fact_prot_info);
 
@@ -2005,13 +2037,19 @@ int mtd_read_fact_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
 			   size_t *retlen, u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_read_fact_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_read_fact_prot_reg(master, from, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_read_fact_prot_reg(master, from, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_read_fact_prot_reg);
 
@@ -2019,12 +2057,18 @@ int mtd_get_user_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
 			   struct otp_info *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_get_user_prot_info)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_get_user_prot_info(master, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret =  master->_get_user_prot_info(master, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_get_user_prot_info);
 
@@ -2032,13 +2076,19 @@ int mtd_read_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
 			   size_t *retlen, u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_read_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_read_user_prot_reg(master, from, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_read_user_prot_reg(master, from, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_read_user_prot_reg);
 
@@ -2053,7 +2103,11 @@ int mtd_write_user_prot_reg(struct mtd_info *mtd, loff_t to, size_t len,
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
+
+	mtd_start_access(master);
 	ret = master->_write_user_prot_reg(master, to, len, retlen, buf);
+	mtd_end_access(master);
+
 	if (ret)
 		return ret;
 
@@ -2068,24 +2122,36 @@ EXPORT_SYMBOL_GPL(mtd_write_user_prot_reg);
 int mtd_lock_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_lock_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_lock_user_prot_reg(master, from, len);
+
+	mtd_start_access(master);
+	ret = master->_lock_user_prot_reg(master, from, len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg);
 
 int mtd_erase_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_erase_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_erase_user_prot_reg(master, from, len);
+
+	mtd_start_access(master);
+	ret = master->_erase_user_prot_reg(master, from, len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg);
 
@@ -2093,6 +2159,7 @@ EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg);
 int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_lock)
 		return -EOPNOTSUPP;
@@ -2106,13 +2173,18 @@ int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_lock);
 
 int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_unlock)
 		return -EOPNOTSUPP;
@@ -2126,13 +2198,18 @@ int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_unlock);
 
 int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_is_locked)
 		return -EOPNOTSUPP;
@@ -2146,13 +2223,18 @@ int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_is_locked);
 
 int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (ofs < 0 || ofs >= mtd->size)
 		return -EINVAL;
@@ -2162,13 +2244,18 @@ int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
-	return master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_start_access(master);
+	ret = master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_block_isreserved);
 
 int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (ofs < 0 || ofs >= mtd->size)
 		return -EINVAL;
@@ -2178,7 +2265,11 @@ int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
-	return master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_start_access(master);
+	ret = master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_block_isbad);
 
@@ -2197,7 +2288,10 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
+	mtd_start_access(master);
 	ret = master->_block_markbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
 	if (ret)
 		return ret;
 
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 88227044fc86..b074106e2d8e 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -231,6 +231,8 @@ struct mtd_master {
 	struct mutex partitions_lock;
 	struct mutex chrdev_lock;
 	unsigned int suspended : 1;
+	wait_queue_head_t resume_wq;
+	struct rw_semaphore suspend_lock;
 };
 
 struct mtd_info {
@@ -476,10 +478,47 @@ static inline u32 mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)
 	return ops->mode == MTD_OPS_AUTO_OOB ? mtd->oobavail : mtd->oobsize;
 }
 
+static inline void mtd_start_access(struct mtd_info *master)
+{
+	WARN_ON_ONCE(master != mtd_get_master(master));
+
+	/*
+	 * Don't take the suspend_lock on devices that don't
+	 * implement the suspend hook. Otherwise, lockdep will
+	 * complain about nested locks when trying to suspend MTD
+	 * partitions or MTD devices created by gluebi which are
+	 * backed by real devices.
+	 */
+	if (!master->_suspend)
+		return;
+
+	/*
+	 * Wait until the device is resumed. Should we have a
+	 * non-blocking mode here?
+	 */
+	while (1) {
+		down_read(&master->master.suspend_lock);
+		if (!master->master.suspended)
+			return;
+
+		up_read(&master->master.suspend_lock);
+		wait_event(master->master.resume_wq, !master->master.suspended);
+	}
+}
+
+static inline void mtd_end_access(struct mtd_info *master)
+{
+	if (!master->_suspend)
+		return;
+
+	up_read(&master->master.suspend_lock);
+}
+
 static inline int mtd_max_bad_blocks(struct mtd_info *mtd,
 				     loff_t ofs, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_max_bad_blocks)
 		return -ENOTSUPP;
@@ -487,8 +526,12 @@ static inline int mtd_max_bad_blocks(struct mtd_info *mtd,
 	if (mtd->size < (len + ofs) || ofs < 0)
 		return -EINVAL;
 
-	return master->_max_bad_blocks(master, mtd_get_master_ofs(mtd, ofs),
-				       len);
+	mtd_start_access(master);
+	ret = master->_max_bad_blocks(master, mtd_get_master_ofs(mtd, ofs),
+				      len);
+	mtd_end_access(master);
+
+	return ret;
 }
 
 int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
@@ -546,30 +589,40 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs);
 static inline int mtd_suspend(struct mtd_info *mtd)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
-	int ret;
-
-	if (master->master.suspended)
-		return 0;
+	int ret = 0;
 
-	ret = master->_suspend ? master->_suspend(master) : 0;
-	if (ret)
+	if (!master->_suspend)
 		return ret;
 
-	master->master.suspended = 1;
-	return 0;
+	down_write(&master->master.suspend_lock);
+	if (!master->master.suspended) {
+		ret = master->_suspend(master);
+		if (!ret)
+			master->master.suspended = 1;
+	}
+	up_write(&master->master.suspend_lock);
+
+	return ret;
 }
 
 static inline void mtd_resume(struct mtd_info *mtd)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
 
-	if (!master->master.suspended)
+	if (!master->_suspend)
 		return;
 
-	if (master->_resume)
-		master->_resume(master);
+	down_write(&master->master.suspend_lock);
+	if (master->master.suspended) {
+		if (master->_resume)
+			master->_resume(master);
+
+		master->master.suspended = 0;
 
-	master->master.suspended = 0;
+		/* The MTD dev has been resumed, wake up all waiters. */
+		wake_up_all(&master->master.resume_wq);
+	}
+	up_write(&master->master.suspend_lock);
 }
 
 static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info *mtd)
-- 
2.33.0

[PATCH v4 3/4] mtd: core: protect access to MTD devices while in suspend

[Sean Nyekjaer]

Prevent MTD access while in a suspended state. Also
prevent suspending a device which is still currently in use.

Commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") allows the
rawnand layer to return errors rather than waiting in a blocking wait.

Tested on a iMX6ULL.

Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
Suggested-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/mtdcore.c   | 124 +++++++++++++++++++++++++++++++++++-----
 include/linux/mtd/mtd.h |  81 +++++++++++++++++++++-----
 2 files changed, 176 insertions(+), 29 deletions(-)

diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
index 153229198947..8e6b7e858ada 100644
--- a/drivers/mtd/mtdcore.c
+++ b/drivers/mtd/mtdcore.c
@@ -777,6 +777,8 @@ static void mtd_set_dev_defaults(struct mtd_info *mtd)
 	INIT_LIST_HEAD(&mtd->partitions);
 	mutex_init(&mtd->master.partitions_lock);
 	mutex_init(&mtd->master.chrdev_lock);
+	init_waitqueue_head(&mtd->master.resume_wq);
+	init_rwsem(&mtd->master.suspend_lock);
 }
 
 static ssize_t mtd_otp_size(struct mtd_info *mtd, bool is_user)
@@ -1267,7 +1269,9 @@ int mtd_erase(struct mtd_info *mtd, struct erase_info *instr)
 
 	adjinstr.addr += mst_ofs;
 
+	mtd_start_access(master);
 	ret = master->_erase(master, &adjinstr);
+	mtd_end_access(master);
 
 	if (adjinstr.fail_addr != MTD_FAIL_ADDR_UNKNOWN) {
 		instr->fail_addr = adjinstr.fail_addr - mst_ofs;
@@ -1289,6 +1293,7 @@ int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	      void **virt, resource_size_t *phys)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	*virt = NULL;
@@ -1301,8 +1306,12 @@ int mtd_point(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	if (!len)
 		return 0;
 
+	mtd_start_access(master);
 	from = mtd_get_master_ofs(mtd, from);
-	return master->_point(master, from, len, retlen, virt, phys);
+	ret = master->_point(master, from, len, retlen, virt, phys);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_point);
 
@@ -1310,6 +1319,7 @@ EXPORT_SYMBOL_GPL(mtd_point);
 int mtd_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_unpoint)
 		return -EOPNOTSUPP;
@@ -1317,7 +1327,12 @@ int mtd_unpoint(struct mtd_info *mtd, loff_t from, size_t len)
 		return -EINVAL;
 	if (!len)
 		return 0;
-	return master->_unpoint(master, mtd_get_master_ofs(mtd, from), len);
+
+	mtd_start_access(master);
+	ret =  master->_unpoint(master, mtd_get_master_ofs(mtd, from), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_unpoint);
 
@@ -1372,6 +1387,7 @@ int mtd_read(struct mtd_info *mtd, loff_t from, size_t len, size_t *retlen,
 	};
 	int ret;
 
+	/* mtd_read_oob_std handles mtd access protection */
 	ret = mtd_read_oob(mtd, from, &ops);
 	*retlen = ops.retlen;
 
@@ -1388,6 +1404,7 @@ int mtd_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	};
 	int ret;
 
+	/* mtd_write_oob_std handles mtd access protection */
 	ret = mtd_write_oob(mtd, to, &ops);
 	*retlen = ops.retlen;
 
@@ -1406,6 +1423,7 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 		    const u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_panic_write)
@@ -1419,8 +1437,12 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
 	if (!master->oops_panic_write)
 		master->oops_panic_write = true;
 
-	return master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
-				    retlen, buf);
+	mtd_start_access(master);
+	ret = master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
+				   retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_panic_write);
 
@@ -1464,11 +1486,13 @@ static int mtd_read_oob_std(struct mtd_info *mtd, loff_t from,
 	int ret;
 
 	from = mtd_get_master_ofs(mtd, from);
+	mtd_start_access(master);
 	if (master->_read_oob)
 		ret = master->_read_oob(master, from, ops);
 	else
 		ret = master->_read(master, from, ops->len, &ops->retlen,
 				    ops->datbuf);
+	mtd_end_access(master);
 
 	return ret;
 }
@@ -1480,11 +1504,13 @@ static int mtd_write_oob_std(struct mtd_info *mtd, loff_t to,
 	int ret;
 
 	to = mtd_get_master_ofs(mtd, to);
+	mtd_start_access(master);
 	if (master->_write_oob)
 		ret = master->_write_oob(master, to, ops);
 	else
 		ret = master->_write(master, to, ops->len, &ops->retlen,
 				     ops->datbuf);
+	mtd_end_access(master);
 
 	return ret;
 }
@@ -1992,12 +2018,18 @@ int mtd_get_fact_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
 			   struct otp_info *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_get_fact_prot_info)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_get_fact_prot_info(master, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_get_fact_prot_info(master, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_get_fact_prot_info);
 
@@ -2005,13 +2037,19 @@ int mtd_read_fact_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
 			   size_t *retlen, u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_read_fact_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_read_fact_prot_reg(master, from, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_read_fact_prot_reg(master, from, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_read_fact_prot_reg);
 
@@ -2019,12 +2057,18 @@ int mtd_get_user_prot_info(struct mtd_info *mtd, size_t len, size_t *retlen,
 			   struct otp_info *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_get_user_prot_info)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_get_user_prot_info(master, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret =  master->_get_user_prot_info(master, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_get_user_prot_info);
 
@@ -2032,13 +2076,19 @@ int mtd_read_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len,
 			   size_t *retlen, u_char *buf)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	*retlen = 0;
 	if (!master->_read_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_read_user_prot_reg(master, from, len, retlen, buf);
+
+	mtd_start_access(master);
+	ret = master->_read_user_prot_reg(master, from, len, retlen, buf);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_read_user_prot_reg);
 
@@ -2053,7 +2103,11 @@ int mtd_write_user_prot_reg(struct mtd_info *mtd, loff_t to, size_t len,
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
+
+	mtd_start_access(master);
 	ret = master->_write_user_prot_reg(master, to, len, retlen, buf);
+	mtd_end_access(master);
+
 	if (ret)
 		return ret;
 
@@ -2068,24 +2122,36 @@ EXPORT_SYMBOL_GPL(mtd_write_user_prot_reg);
 int mtd_lock_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_lock_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_lock_user_prot_reg(master, from, len);
+
+	mtd_start_access(master);
+	ret = master->_lock_user_prot_reg(master, from, len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_lock_user_prot_reg);
 
 int mtd_erase_user_prot_reg(struct mtd_info *mtd, loff_t from, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_erase_user_prot_reg)
 		return -EOPNOTSUPP;
 	if (!len)
 		return 0;
-	return master->_erase_user_prot_reg(master, from, len);
+
+	mtd_start_access(master);
+	ret = master->_erase_user_prot_reg(master, from, len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg);
 
@@ -2093,6 +2159,7 @@ EXPORT_SYMBOL_GPL(mtd_erase_user_prot_reg);
 int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_lock)
 		return -EOPNOTSUPP;
@@ -2106,13 +2173,18 @@ int mtd_lock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_lock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_lock);
 
 int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_unlock)
 		return -EOPNOTSUPP;
@@ -2126,13 +2198,18 @@ int mtd_unlock(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_unlock(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_unlock);
 
 int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_is_locked)
 		return -EOPNOTSUPP;
@@ -2146,13 +2223,18 @@ int mtd_is_locked(struct mtd_info *mtd, loff_t ofs, uint64_t len)
 		len = (u64)mtd_div_by_eb(len, mtd) * master->erasesize;
 	}
 
-	return master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_start_access(master);
+	ret = master->_is_locked(master, mtd_get_master_ofs(mtd, ofs), len);
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_is_locked);
 
 int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (ofs < 0 || ofs >= mtd->size)
 		return -EINVAL;
@@ -2162,13 +2244,18 @@ int mtd_block_isreserved(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
-	return master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_start_access(master);
+	ret = master->_block_isreserved(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_block_isreserved);
 
 int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (ofs < 0 || ofs >= mtd->size)
 		return -EINVAL;
@@ -2178,7 +2265,11 @@ int mtd_block_isbad(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
-	return master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_start_access(master);
+	ret = master->_block_isbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(mtd_block_isbad);
 
@@ -2197,7 +2288,10 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs)
 	if (mtd->flags & MTD_SLC_ON_MLC_EMULATION)
 		ofs = (loff_t)mtd_div_by_eb(ofs, mtd) * master->erasesize;
 
+	mtd_start_access(master);
 	ret = master->_block_markbad(master, mtd_get_master_ofs(mtd, ofs));
+	mtd_end_access(master);
+
 	if (ret)
 		return ret;
 
diff --git a/include/linux/mtd/mtd.h b/include/linux/mtd/mtd.h
index 88227044fc86..b074106e2d8e 100644
--- a/include/linux/mtd/mtd.h
+++ b/include/linux/mtd/mtd.h
@@ -231,6 +231,8 @@ struct mtd_master {
 	struct mutex partitions_lock;
 	struct mutex chrdev_lock;
 	unsigned int suspended : 1;
+	wait_queue_head_t resume_wq;
+	struct rw_semaphore suspend_lock;
 };
 
 struct mtd_info {
@@ -476,10 +478,47 @@ static inline u32 mtd_oobavail(struct mtd_info *mtd, struct mtd_oob_ops *ops)
 	return ops->mode == MTD_OPS_AUTO_OOB ? mtd->oobavail : mtd->oobsize;
 }
 
+static inline void mtd_start_access(struct mtd_info *master)
+{
+	WARN_ON_ONCE(master != mtd_get_master(master));
+
+	/*
+	 * Don't take the suspend_lock on devices that don't
+	 * implement the suspend hook. Otherwise, lockdep will
+	 * complain about nested locks when trying to suspend MTD
+	 * partitions or MTD devices created by gluebi which are
+	 * backed by real devices.
+	 */
+	if (!master->_suspend)
+		return;
+
+	/*
+	 * Wait until the device is resumed. Should we have a
+	 * non-blocking mode here?
+	 */
+	while (1) {
+		down_read(&master->master.suspend_lock);
+		if (!master->master.suspended)
+			return;
+
+		up_read(&master->master.suspend_lock);
+		wait_event(master->master.resume_wq, !master->master.suspended);
+	}
+}
+
+static inline void mtd_end_access(struct mtd_info *master)
+{
+	if (!master->_suspend)
+		return;
+
+	up_read(&master->master.suspend_lock);
+}
+
 static inline int mtd_max_bad_blocks(struct mtd_info *mtd,
 				     loff_t ofs, size_t len)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
+	int ret;
 
 	if (!master->_max_bad_blocks)
 		return -ENOTSUPP;
@@ -487,8 +526,12 @@ static inline int mtd_max_bad_blocks(struct mtd_info *mtd,
 	if (mtd->size < (len + ofs) || ofs < 0)
 		return -EINVAL;
 
-	return master->_max_bad_blocks(master, mtd_get_master_ofs(mtd, ofs),
-				       len);
+	mtd_start_access(master);
+	ret = master->_max_bad_blocks(master, mtd_get_master_ofs(mtd, ofs),
+				      len);
+	mtd_end_access(master);
+
+	return ret;
 }
 
 int mtd_wunit_to_pairing_info(struct mtd_info *mtd, int wunit,
@@ -546,30 +589,40 @@ int mtd_block_markbad(struct mtd_info *mtd, loff_t ofs);
 static inline int mtd_suspend(struct mtd_info *mtd)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
-	int ret;
-
-	if (master->master.suspended)
-		return 0;
+	int ret = 0;
 
-	ret = master->_suspend ? master->_suspend(master) : 0;
-	if (ret)
+	if (!master->_suspend)
 		return ret;
 
-	master->master.suspended = 1;
-	return 0;
+	down_write(&master->master.suspend_lock);
+	if (!master->master.suspended) {
+		ret = master->_suspend(master);
+		if (!ret)
+			master->master.suspended = 1;
+	}
+	up_write(&master->master.suspend_lock);
+
+	return ret;
 }
 
 static inline void mtd_resume(struct mtd_info *mtd)
 {
 	struct mtd_info *master = mtd_get_master(mtd);
 
-	if (!master->master.suspended)
+	if (!master->_suspend)
 		return;
 
-	if (master->_resume)
-		master->_resume(master);
+	down_write(&master->master.suspend_lock);
+	if (master->master.suspended) {
+		if (master->_resume)
+			master->_resume(master);
+
+		master->master.suspended = 0;
 
-	master->master.suspended = 0;
+		/* The MTD dev has been resumed, wake up all waiters. */
+		wake_up_all(&master->master.resume_wq);
+	}
+	up_write(&master->master.suspend_lock);
 }
 
 static inline uint32_t mtd_div_by_eb(uint64_t sz, struct mtd_info *mtd)
-- 
2.33.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

[PATCH v4 4/4] mtd: rawnand: remove suspended check

[Sean Nyekjaer]

Access is protected in upper MTD layer when MTD devices are suspended.

Commit ("mtd: core: protect access to MTD devices while in suspend")
introduces access protection, so it's safe to remove suspended checks.

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/nand/raw/nand_base.c | 52 ++++++++------------------------
 include/linux/mtd/rawnand.h      |  5 +--
 2 files changed, 14 insertions(+), 43 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 3d6c6e880520..aa2874ae3c4a 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -332,19 +332,11 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
  * @chip: NAND chip structure
  *
  * Lock the device and its controller for exclusive access
- *
- * Return: -EBUSY if the chip has been suspended, 0 otherwise
  */
-static int nand_get_device(struct nand_chip *chip)
+static void nand_get_device(struct nand_chip *chip)
 {
 	mutex_lock(&chip->lock);
-	if (chip->suspended) {
-		mutex_unlock(&chip->lock);
-		return -EBUSY;
-	}
 	mutex_lock(&chip->controller->lock);
-
-	return 0;
 }
 
 /**
@@ -573,10 +565,7 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
 		nand_erase_nand(chip, &einfo, 0);
 
 		/* Write bad block marker to OOB */
-		ret = nand_get_device(chip);
-		if (ret)
-			return ret;
-
+		nand_get_device(chip);
 		ret = nand_markbad_bbm(chip, ofs);
 		nand_release_device(chip);
 	}
@@ -3756,9 +3745,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 	    ops->mode != MTD_OPS_RAW)
 		return -ENOTSUPP;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	if (!ops->datbuf)
 		ret = nand_do_read_oob(chip, from, ops);
@@ -4345,13 +4332,11 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
 			  struct mtd_oob_ops *ops)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
-	int ret;
+	int ret = 0;
 
 	ops->retlen = 0;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	switch (ops->mode) {
 	case MTD_OPS_PLACE_OOB:
@@ -4410,10 +4395,8 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
 	if (nand_region_is_secured(chip, instr->addr, instr->len))
 		return -EIO;
 
-	/* Grab the lock and see if the device is available */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	/* Grab the lock */
+	nand_get_device(chip);
 
 	/* Shift to get first page */
 	page = (int)(instr->addr >> chip->page_shift);
@@ -4499,8 +4482,8 @@ static void nand_sync(struct mtd_info *mtd)
 
 	pr_debug("%s: called\n", __func__);
 
-	/* Grab the lock and see if the device is available */
-	WARN_ON(nand_get_device(chip));
+	/* Grab the lock */
+	nand_get_device(chip);
 	/* Release it and go back */
 	nand_release_device(chip);
 }
@@ -4517,9 +4500,7 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
 	int ret;
 
 	/* Select the NAND device */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	nand_select_target(chip, chipnr);
 
@@ -4565,8 +4546,6 @@ static int nand_suspend(struct mtd_info *mtd)
 	mutex_lock(&chip->lock);
 	if (chip->ops.suspend)
 		ret = chip->ops.suspend(chip);
-	if (!ret)
-		chip->suspended = 1;
 	mutex_unlock(&chip->lock);
 
 	return ret;
@@ -4580,15 +4559,10 @@ static void nand_resume(struct mtd_info *mtd)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 
+
 	mutex_lock(&chip->lock);
-	if (chip->suspended) {
-		if (chip->ops.resume)
-			chip->ops.resume(chip);
-		chip->suspended = 0;
-	} else {
-		pr_err("%s called for a chip which is not in suspended state\n",
-			__func__);
-	}
+	if (chip->ops.resume)
+		chip->ops.resume(chip);
 	mutex_unlock(&chip->lock);
 }
 
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index b2f9dd3cbd69..1198a6548912 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1237,9 +1237,7 @@ struct nand_secure_region {
  * @pagecache.page: Page number currently in the cache. -1 means no page is
  *                  currently cached
  * @buf_align: Minimum buffer alignment required by a platform
- * @lock: Lock protecting the suspended field. Also used to serialize accesses
- *        to the NAND device
- * @suspended: Set to 1 when the device is suspended, 0 when it's not
+ * @lock: Lock to serialize accesses to the NAND device
  * @cur_cs: Currently selected target. -1 means no target selected, otherwise we
  *          should always have cur_cs >= 0 && cur_cs < nanddev_ntargets().
  *          NAND Controller drivers should not modify this value, but they're
@@ -1293,7 +1291,6 @@ struct nand_chip {
 
 	/* Internals */
 	struct mutex lock;
-	unsigned int suspended : 1;
 	int cur_cs;
 	int read_retries;
 	struct nand_secure_region *secure_regions;
-- 
2.33.0

[PATCH v4 4/4] mtd: rawnand: remove suspended check

[Sean Nyekjaer]

Access is protected in upper MTD layer when MTD devices are suspended.

Commit ("mtd: core: protect access to MTD devices while in suspend")
introduces access protection, so it's safe to remove suspended checks.

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Sean Nyekjaer <sean@geanix.com>
---
 drivers/mtd/nand/raw/nand_base.c | 52 ++++++++------------------------
 include/linux/mtd/rawnand.h      |  5 +--
 2 files changed, 14 insertions(+), 43 deletions(-)

diff --git a/drivers/mtd/nand/raw/nand_base.c b/drivers/mtd/nand/raw/nand_base.c
index 3d6c6e880520..aa2874ae3c4a 100644
--- a/drivers/mtd/nand/raw/nand_base.c
+++ b/drivers/mtd/nand/raw/nand_base.c
@@ -332,19 +332,11 @@ static int nand_isbad_bbm(struct nand_chip *chip, loff_t ofs)
  * @chip: NAND chip structure
  *
  * Lock the device and its controller for exclusive access
- *
- * Return: -EBUSY if the chip has been suspended, 0 otherwise
  */
-static int nand_get_device(struct nand_chip *chip)
+static void nand_get_device(struct nand_chip *chip)
 {
 	mutex_lock(&chip->lock);
-	if (chip->suspended) {
-		mutex_unlock(&chip->lock);
-		return -EBUSY;
-	}
 	mutex_lock(&chip->controller->lock);
-
-	return 0;
 }
 
 /**
@@ -573,10 +565,7 @@ static int nand_block_markbad_lowlevel(struct nand_chip *chip, loff_t ofs)
 		nand_erase_nand(chip, &einfo, 0);
 
 		/* Write bad block marker to OOB */
-		ret = nand_get_device(chip);
-		if (ret)
-			return ret;
-
+		nand_get_device(chip);
 		ret = nand_markbad_bbm(chip, ofs);
 		nand_release_device(chip);
 	}
@@ -3756,9 +3745,7 @@ static int nand_read_oob(struct mtd_info *mtd, loff_t from,
 	    ops->mode != MTD_OPS_RAW)
 		return -ENOTSUPP;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	if (!ops->datbuf)
 		ret = nand_do_read_oob(chip, from, ops);
@@ -4345,13 +4332,11 @@ static int nand_write_oob(struct mtd_info *mtd, loff_t to,
 			  struct mtd_oob_ops *ops)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
-	int ret;
+	int ret = 0;
 
 	ops->retlen = 0;
 
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	switch (ops->mode) {
 	case MTD_OPS_PLACE_OOB:
@@ -4410,10 +4395,8 @@ int nand_erase_nand(struct nand_chip *chip, struct erase_info *instr,
 	if (nand_region_is_secured(chip, instr->addr, instr->len))
 		return -EIO;
 
-	/* Grab the lock and see if the device is available */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	/* Grab the lock */
+	nand_get_device(chip);
 
 	/* Shift to get first page */
 	page = (int)(instr->addr >> chip->page_shift);
@@ -4499,8 +4482,8 @@ static void nand_sync(struct mtd_info *mtd)
 
 	pr_debug("%s: called\n", __func__);
 
-	/* Grab the lock and see if the device is available */
-	WARN_ON(nand_get_device(chip));
+	/* Grab the lock */
+	nand_get_device(chip);
 	/* Release it and go back */
 	nand_release_device(chip);
 }
@@ -4517,9 +4500,7 @@ static int nand_block_isbad(struct mtd_info *mtd, loff_t offs)
 	int ret;
 
 	/* Select the NAND device */
-	ret = nand_get_device(chip);
-	if (ret)
-		return ret;
+	nand_get_device(chip);
 
 	nand_select_target(chip, chipnr);
 
@@ -4565,8 +4546,6 @@ static int nand_suspend(struct mtd_info *mtd)
 	mutex_lock(&chip->lock);
 	if (chip->ops.suspend)
 		ret = chip->ops.suspend(chip);
-	if (!ret)
-		chip->suspended = 1;
 	mutex_unlock(&chip->lock);
 
 	return ret;
@@ -4580,15 +4559,10 @@ static void nand_resume(struct mtd_info *mtd)
 {
 	struct nand_chip *chip = mtd_to_nand(mtd);
 
+
 	mutex_lock(&chip->lock);
-	if (chip->suspended) {
-		if (chip->ops.resume)
-			chip->ops.resume(chip);
-		chip->suspended = 0;
-	} else {
-		pr_err("%s called for a chip which is not in suspended state\n",
-			__func__);
-	}
+	if (chip->ops.resume)
+		chip->ops.resume(chip);
 	mutex_unlock(&chip->lock);
 }
 
diff --git a/include/linux/mtd/rawnand.h b/include/linux/mtd/rawnand.h
index b2f9dd3cbd69..1198a6548912 100644
--- a/include/linux/mtd/rawnand.h
+++ b/include/linux/mtd/rawnand.h
@@ -1237,9 +1237,7 @@ struct nand_secure_region {
  * @pagecache.page: Page number currently in the cache. -1 means no page is
  *                  currently cached
  * @buf_align: Minimum buffer alignment required by a platform
- * @lock: Lock protecting the suspended field. Also used to serialize accesses
- *        to the NAND device
- * @suspended: Set to 1 when the device is suspended, 0 when it's not
+ * @lock: Lock to serialize accesses to the NAND device
  * @cur_cs: Currently selected target. -1 means no target selected, otherwise we
  *          should always have cur_cs >= 0 && cur_cs < nanddev_ntargets().
  *          NAND Controller drivers should not modify this value, but they're
@@ -1293,7 +1291,6 @@ struct nand_chip {
 
 	/* Internals */
 	struct mutex lock;
-	unsigned int suspended : 1;
 	int cur_cs;
 	int read_retries;
 	struct nand_secure_region *secure_regions;
-- 
2.33.0


______________________________________________________
Linux MTD discussion mailing list
http://lists.infradead.org/mailman/listinfo/linux-mtd/

Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:48 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> From: Boris Brezillon <boris.brezillon@collabora.com>
> 
> The BBT scan logic use the MTD helpers before the MTD layer had a
> chance to initialize the device, and that leads to issues when
> accessing the uninitialized suspend lock. Let's temporarily set the
> suspend/resume hooks to NULL to skip the lock acquire/release step.
> 
> Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")

I think I already mentioned this Fixes tag should not be there.

> Tested-by: Sean Nyekjaer <sean@geanix.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>
> ---
>  drivers/mtd/nand/raw/nand_bbt.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
> index b7ad030225f8..93d385703469 100644
> --- a/drivers/mtd/nand/raw/nand_bbt.c
> +++ b/drivers/mtd/nand/raw/nand_bbt.c
> @@ -1397,8 +1397,28 @@ static int nand_create_badblock_pattern(struct nand_chip *this)
>   */
>  int nand_create_bbt(struct nand_chip *this)
>  {
> +	struct mtd_info *mtd = nand_to_mtd(this);
> +	int (*suspend) (struct mtd_info *) = mtd->_suspend;
> +	void (*resume) (struct mtd_info *) = mtd->_resume;
>  	int ret;
>  
> +	/*
> +	 * The BBT scan logic use the MTD helpers before the MTD layer had a
> +	 * chance to initialize the device, and that leads to issues when
> +	 * accessing the uninitialized suspend lock. Let's temporarily set the
> +	 * suspend/resume hooks to NULL to skip the lock acquire/release step.
> +	 *
> +	 * FIXME: This is an ugly hack, so please don't copy this pattern to
> +	 * other MTD implementations. The proper fix would be to implement a
> +	 * generic BBT scan logic at the NAND level that's not using any of the
> +	 * MTD helpers to access pages. We also might consider doing a two
> +	 * step initialization at the MTD level (mtd_device_init() +
> +	 * mtd_device_register()) so some of the fields are initialized
> +	 * early.
> +	 */
> +	mtd->_suspend = NULL;
> +	mtd->_resume = NULL;
> +
>  	/* Is a flash based bad block table requested? */
>  	if (this->bbt_options & NAND_BBT_USE_FLASH) {
>  		/* Use the default pattern descriptors */
> @@ -1422,7 +1442,13 @@ int nand_create_bbt(struct nand_chip *this)
>  			return ret;
>  	}
>  
> -	return nand_scan_bbt(this, this->badblock_pattern);
> +	ret = nand_scan_bbt(this, this->badblock_pattern);
> +
> +	/* Restore the suspend/resume hooks. */
> +	mtd->_suspend = suspend;
> +	mtd->_resume = resume;
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(nand_create_bbt);
>  

Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:48 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> From: Boris Brezillon <boris.brezillon@collabora.com>
> 
> The BBT scan logic use the MTD helpers before the MTD layer had a
> chance to initialize the device, and that leads to issues when
> accessing the uninitialized suspend lock. Let's temporarily set the
> suspend/resume hooks to NULL to skip the lock acquire/release step.
> 
> Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")

I think I already mentioned this Fixes tag should not be there.

> Tested-by: Sean Nyekjaer <sean@geanix.com>
> Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
> Signed-off-by: Sean Nyekjaer <sean@geanix.com>
> ---
>  drivers/mtd/nand/raw/nand_bbt.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/mtd/nand/raw/nand_bbt.c b/drivers/mtd/nand/raw/nand_bbt.c
> index b7ad030225f8..93d385703469 100644
> --- a/drivers/mtd/nand/raw/nand_bbt.c
> +++ b/drivers/mtd/nand/raw/nand_bbt.c
> @@ -1397,8 +1397,28 @@ static int nand_create_badblock_pattern(struct nand_chip *this)
>   */
>  int nand_create_bbt(struct nand_chip *this)
>  {
> +	struct mtd_info *mtd = nand_to_mtd(this);
> +	int (*suspend) (struct mtd_info *) = mtd->_suspend;
> +	void (*resume) (struct mtd_info *) = mtd->_resume;
>  	int ret;
>  
> +	/*
> +	 * The BBT scan logic use the MTD helpers before the MTD layer had a
> +	 * chance to initialize the device, and that leads to issues when
> +	 * accessing the uninitialized suspend lock. Let's temporarily set the
> +	 * suspend/resume hooks to NULL to skip the lock acquire/release step.
> +	 *
> +	 * FIXME: This is an ugly hack, so please don't copy this pattern to
> +	 * other MTD implementations. The proper fix would be to implement a
> +	 * generic BBT scan logic at the NAND level that's not using any of the
> +	 * MTD helpers to access pages. We also might consider doing a two
> +	 * step initialization at the MTD level (mtd_device_init() +
> +	 * mtd_device_register()) so some of the fields are initialized
> +	 * early.
> +	 */
> +	mtd->_suspend = NULL;
> +	mtd->_resume = NULL;
> +
>  	/* Is a flash based bad block table requested? */
>  	if (this->bbt_options & NAND_BBT_USE_FLASH) {
>  		/* Use the default pattern descriptors */
> @@ -1422,7 +1442,13 @@ int nand_create_bbt(struct nand_chip *this)
>  			return ret;
>  	}
>  
> -	return nand_scan_bbt(this, this->badblock_pattern);
> +	ret = nand_scan_bbt(this, this->badblock_pattern);
> +
> +	/* Restore the suspend/resume hooks. */
> +	mtd->_suspend = suspend;
> +	mtd->_resume = resume;
> +
> +	return ret;
>  }
>  EXPORT_SYMBOL(nand_create_bbt);
>  


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Re: [PATCH v4 3/4] mtd: core: protect access to MTD devices while in suspend

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:50 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> @@ -1406,6 +1423,7 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  		    const u_char *buf)
>  {
>  	struct mtd_info *master = mtd_get_master(mtd);
> +	int ret;
>  
>  	*retlen = 0;
>  	if (!master->_panic_write)
> @@ -1419,8 +1437,12 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  	if (!master->oops_panic_write)
>  		master->oops_panic_write = true;
>  
> -	return master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> -				    retlen, buf);
> +	mtd_start_access(master);
> +	ret = master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> +				   retlen, buf);
> +	mtd_end_access(master);
> +
> +	return ret;
>  }

I suspect panic_write should be an exception, otherwise a panic in the
suspend path would never be able to write its data to the flash.

Re: [PATCH v4 3/4] mtd: core: protect access to MTD devices while in suspend

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:50 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> @@ -1406,6 +1423,7 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  		    const u_char *buf)
>  {
>  	struct mtd_info *master = mtd_get_master(mtd);
> +	int ret;
>  
>  	*retlen = 0;
>  	if (!master->_panic_write)
> @@ -1419,8 +1437,12 @@ int mtd_panic_write(struct mtd_info *mtd, loff_t to, size_t len, size_t *retlen,
>  	if (!master->oops_panic_write)
>  		master->oops_panic_write = true;
>  
> -	return master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> -				    retlen, buf);
> +	mtd_start_access(master);
> +	ret = master->_panic_write(master, mtd_get_master_ofs(mtd, to), len,
> +				   retlen, buf);
> +	mtd_end_access(master);
> +
> +	return ret;
>  }

I suspect panic_write should be an exception, otherwise a panic in the
suspend path would never be able to write its data to the flash.

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Re: [PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:47 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> Follow-up on discussion in:
> https://lkml.org/lkml/2021/10/4/41
> https://lkml.org/lkml/2021/10/11/435
> 
> Changes since v3:
>  - edited commit msg and author for mtdconcat patch
> 
> Changes since v2:
>  - added signoff's to patch from Boris
>  - removed accidential line break
>  - kept tests consistent: master->master.suspended == 0 -> !master->master.suspended
>  - added comments to mtdconcat patch
>  - moved mtdconcat before ('mtd: core: protect access to MTD devices while in suspend')
> 
> Changes since v1:
>  - removed __mtd_suspend/__mtd_resume functions as they are not used by
>    mtdconcat anymore.
>  - only master mtd_info is used for mtd_{start,end}_access(). Warn if we
>    got mtd's.
>  - added Boris patch for using uninitialized _suspend/_resume hooks when
>    bbt scanning
>  - mtdconcat uses device _suspend/_resume hooks
>  - I don't really like the macro proposal from Boris
>    mtd_no_suspend_void_call()/mtd_no_suspend_ret_call() I think they
>    make the code complex to read and the macro's doesn't fit every
>    where anyway...
> 
> Changes since from rfc v1/v2:
>  - added access protection for all device access hooks in mtd_info.
>  - added Suggested-by to [1/3] patch.
>  - removed refereces to commit ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
>    from commit msg as commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") is 
>    to be blamed.
>  - tested on a kernel with LOCKDEP enabled.
> 
> Boris Brezillon (2):
>   mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt
>   mtd: mtdconcat: don't use mtd_{suspend,resume}()
> 
> Sean Nyekjaer (2):
>   mtd: core: protect access to MTD devices while in suspend
>   mtd: rawnand: remove suspended check

Looks good overall (after fixing the minor things I pointed out, of
course), but I'd recommend applying this series to mtd-next just after
-rc1 is out so you get a chance to detect regressions before it's
merged in Linus' tree. I fear this unconditional blocking on suspended
device will lead to unexpected deadlocks (see my comment on panic
writes)...

> 
>  drivers/mtd/mtdconcat.c          |  15 +++-
>  drivers/mtd/mtdcore.c            | 124 +++++++++++++++++++++++++++----
>  drivers/mtd/nand/raw/nand_base.c |  52 ++++---------
>  drivers/mtd/nand/raw/nand_bbt.c  |  28 ++++++-
>  include/linux/mtd/mtd.h          |  81 ++++++++++++++++----
>  include/linux/mtd/rawnand.h      |   5 +-
>  6 files changed, 230 insertions(+), 75 deletions(-)
> 

Re: [PATCH v4 0/4] mtd: core: protect access to mtd devices while in suspend

[Boris Brezillon]

On Tue, 26 Oct 2021 07:55:47 +0200
Sean Nyekjaer <sean@geanix.com> wrote:

> Follow-up on discussion in:
> https://lkml.org/lkml/2021/10/4/41
> https://lkml.org/lkml/2021/10/11/435
> 
> Changes since v3:
>  - edited commit msg and author for mtdconcat patch
> 
> Changes since v2:
>  - added signoff's to patch from Boris
>  - removed accidential line break
>  - kept tests consistent: master->master.suspended == 0 -> !master->master.suspended
>  - added comments to mtdconcat patch
>  - moved mtdconcat before ('mtd: core: protect access to MTD devices while in suspend')
> 
> Changes since v1:
>  - removed __mtd_suspend/__mtd_resume functions as they are not used by
>    mtdconcat anymore.
>  - only master mtd_info is used for mtd_{start,end}_access(). Warn if we
>    got mtd's.
>  - added Boris patch for using uninitialized _suspend/_resume hooks when
>    bbt scanning
>  - mtdconcat uses device _suspend/_resume hooks
>  - I don't really like the macro proposal from Boris
>    mtd_no_suspend_void_call()/mtd_no_suspend_ret_call() I think they
>    make the code complex to read and the macro's doesn't fit every
>    where anyway...
> 
> Changes since from rfc v1/v2:
>  - added access protection for all device access hooks in mtd_info.
>  - added Suggested-by to [1/3] patch.
>  - removed refereces to commit ef347c0cfd61 ("mtd: rawnand: gpmi: Implement exec_op")
>    from commit msg as commit 013e6292aaf5 ("mtd: rawnand: Simplify the locking") is 
>    to be blamed.
>  - tested on a kernel with LOCKDEP enabled.
> 
> Boris Brezillon (2):
>   mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt
>   mtd: mtdconcat: don't use mtd_{suspend,resume}()
> 
> Sean Nyekjaer (2):
>   mtd: core: protect access to MTD devices while in suspend
>   mtd: rawnand: remove suspended check

Looks good overall (after fixing the minor things I pointed out, of
course), but I'd recommend applying this series to mtd-next just after
-rc1 is out so you get a chance to detect regressions before it's
merged in Linus' tree. I fear this unconditional blocking on suspended
device will lead to unexpected deadlocks (see my comment on panic
writes)...

> 
>  drivers/mtd/mtdconcat.c          |  15 +++-
>  drivers/mtd/mtdcore.c            | 124 +++++++++++++++++++++++++++----
>  drivers/mtd/nand/raw/nand_base.c |  52 ++++---------
>  drivers/mtd/nand/raw/nand_bbt.c  |  28 ++++++-
>  include/linux/mtd/mtd.h          |  81 ++++++++++++++++----
>  include/linux/mtd/rawnand.h      |   5 +-
>  6 files changed, 230 insertions(+), 75 deletions(-)
> 


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Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Sean Nyekjaer]

On Mon, Nov 01, 2021 at 08:38:24AM +0100, Boris Brezillon wrote:
> On Tue, 26 Oct 2021 07:55:48 +0200
> Sean Nyekjaer <sean@geanix.com> wrote:
> 
> > From: Boris Brezillon <boris.brezillon@collabora.com>
> > 
> > The BBT scan logic use the MTD helpers before the MTD layer had a
> > chance to initialize the device, and that leads to issues when
> > accessing the uninitialized suspend lock. Let's temporarily set the
> > suspend/resume hooks to NULL to skip the lock acquire/release step.
> > 
> > Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
> 
> I think I already mentioned this Fixes tag should not be there.
> 

No, I didn't recall that, but nevermind :)

Hmm when ('mtd: core: protect access to MTD devices while in suspend')
is backported we want to live with the use before init of the rwsem?

/Sean

Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Sean Nyekjaer]

On Mon, Nov 01, 2021 at 08:38:24AM +0100, Boris Brezillon wrote:
> On Tue, 26 Oct 2021 07:55:48 +0200
> Sean Nyekjaer <sean@geanix.com> wrote:
> 
> > From: Boris Brezillon <boris.brezillon@collabora.com>
> > 
> > The BBT scan logic use the MTD helpers before the MTD layer had a
> > chance to initialize the device, and that leads to issues when
> > accessing the uninitialized suspend lock. Let's temporarily set the
> > suspend/resume hooks to NULL to skip the lock acquire/release step.
> > 
> > Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")
> 
> I think I already mentioned this Fixes tag should not be there.
> 

No, I didn't recall that, but nevermind :)

Hmm when ('mtd: core: protect access to MTD devices while in suspend')
is backported we want to live with the use before init of the rwsem?

/Sean

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Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Boris Brezillon]

On Mon, 1 Nov 2021 09:46:23 +0100
Sean Nyekjaer <sean@geanix.com> wrote:

> On Mon, Nov 01, 2021 at 08:38:24AM +0100, Boris Brezillon wrote:
> > On Tue, 26 Oct 2021 07:55:48 +0200
> > Sean Nyekjaer <sean@geanix.com> wrote:
> >   
> > > From: Boris Brezillon <boris.brezillon@collabora.com>
> > > 
> > > The BBT scan logic use the MTD helpers before the MTD layer had a
> > > chance to initialize the device, and that leads to issues when
> > > accessing the uninitialized suspend lock. Let's temporarily set the
> > > suspend/resume hooks to NULL to skip the lock acquire/release step.
> > > 
> > > Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")  
> > 
> > I think I already mentioned this Fixes tag should not be there.
> >   
> 
> No, I didn't recall that, but nevermind :)
> 
> Hmm when ('mtd: core: protect access to MTD devices while in suspend')
> is backported we want to live with the use before init of the rwsem?

It's not meant to be backported. You'll need something simpler...

> 
> /Sean

Re: [PATCH v4 1/4] mtd: rawnand: nand_bbt: hide suspend/resume hooks while scanning bbt

[Boris Brezillon]

On Mon, 1 Nov 2021 09:46:23 +0100
Sean Nyekjaer <sean@geanix.com> wrote:

> On Mon, Nov 01, 2021 at 08:38:24AM +0100, Boris Brezillon wrote:
> > On Tue, 26 Oct 2021 07:55:48 +0200
> > Sean Nyekjaer <sean@geanix.com> wrote:
> >   
> > > From: Boris Brezillon <boris.brezillon@collabora.com>
> > > 
> > > The BBT scan logic use the MTD helpers before the MTD layer had a
> > > chance to initialize the device, and that leads to issues when
> > > accessing the uninitialized suspend lock. Let's temporarily set the
> > > suspend/resume hooks to NULL to skip the lock acquire/release step.
> > > 
> > > Fixes: 013e6292aaf5 ("mtd: rawnand: Simplify the locking")  
> > 
> > I think I already mentioned this Fixes tag should not be there.
> >   
> 
> No, I didn't recall that, but nevermind :)
> 
> Hmm when ('mtd: core: protect access to MTD devices while in suspend')
> is backported we want to live with the use before init of the rwsem?

It's not meant to be backported. You'll need something simpler...

> 
> /Sean


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