[PATCH stable-5.15.y 0/4] backport test case btrfs/216 fixes

[PATCH stable-5.15.y 0/4] backport test case btrfs/216 fixes

[Anand Jain]

In an attempt to make all the fstests test cases pass on stable-5.15.y,
backport fixes for the test case btrfs/216.

Anand Jain (4):
  btrfs: convert latest_bdev type to btrfs_device and rename
  btrfs: use latest_dev in btrfs_show_devname
  btrfs: update latest_dev when we create a sprout device
  btrfs: remove stale comment about the btrfs_show_devname

 fs/btrfs/disk-io.c   |  6 +++---
 fs/btrfs/extent_io.c |  2 +-
 fs/btrfs/inode.c     |  2 +-
 fs/btrfs/super.c     | 26 ++++++--------------------
 fs/btrfs/volumes.c   | 19 +++++++------------
 fs/btrfs/volumes.h   |  6 +++++-
 6 files changed, 23 insertions(+), 38 deletions(-)

-- 
2.33.1

[PATCH stable-5.15.y 1/4] btrfs: convert latest_bdev type to btrfs_device and rename

[Anand Jain]

Commit d24fa5c1da08026be9959baca309fa0adf8708bf upstream.

In preparation to fix a bug in btrfs_show_devname().

Convert fs_devices::latest_bdev type from struct block_device to struct
btrfs_device and, rename the member to fs_devices::latest_dev.
So that btrfs_show_devname() can use fs_devices::latest_dev::name.

Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/disk-io.c   |  6 +++---
 fs/btrfs/extent_io.c |  2 +-
 fs/btrfs/inode.c     |  2 +-
 fs/btrfs/super.c     |  2 +-
 fs/btrfs/volumes.c   | 10 +++++-----
 fs/btrfs/volumes.h   |  6 +++++-
 6 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index e00c4c1f622f..244cddf050d1 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3229,12 +3229,12 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	mapping_set_gfp_mask(fs_info->btree_inode->i_mapping, GFP_NOFS);
 	btrfs_init_btree_inode(fs_info);
 
-	invalidate_bdev(fs_devices->latest_bdev);
+	invalidate_bdev(fs_devices->latest_dev->bdev);
 
 	/*
 	 * Read super block and check the signature bytes only
 	 */
-	disk_super = btrfs_read_dev_super(fs_devices->latest_bdev);
+	disk_super = btrfs_read_dev_super(fs_devices->latest_dev->bdev);
 	if (IS_ERR(disk_super)) {
 		err = PTR_ERR(disk_super);
 		goto fail_alloc;
@@ -3466,7 +3466,7 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 	 * below in btrfs_init_dev_replace().
 	 */
 	btrfs_free_extra_devids(fs_devices);
-	if (!fs_devices->latest_bdev) {
+	if (!fs_devices->latest_dev->bdev) {
 		btrfs_err(fs_info, "failed to read devices");
 		goto fail_tree_roots;
 	}
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a40fb9c74dda..3c7ee83e9199 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3327,7 +3327,7 @@ static int alloc_new_bio(struct btrfs_inode *inode,
 	if (wbc) {
 		struct block_device *bdev;
 
-		bdev = fs_info->fs_devices->latest_bdev;
+		bdev = fs_info->fs_devices->latest_dev->bdev;
 		bio_set_dev(bio, bdev);
 		wbc_init_bio(wbc, bio);
 	}
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 61b4651f008d..4af74b62e7d9 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7967,7 +7967,7 @@ static int btrfs_dio_iomap_begin(struct inode *inode, loff_t start,
 		iomap->type = IOMAP_MAPPED;
 	}
 	iomap->offset = start;
-	iomap->bdev = fs_info->fs_devices->latest_bdev;
+	iomap->bdev = fs_info->fs_devices->latest_dev->bdev;
 	iomap->length = len;
 
 	if (write && btrfs_use_zone_append(BTRFS_I(inode), em->block_start))
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 537d90bf5d84..e4963da4dd08 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1705,7 +1705,7 @@ static struct dentry *btrfs_mount_root(struct file_system_type *fs_type,
 		goto error_close_devices;
 	}
 
-	bdev = fs_devices->latest_bdev;
+	bdev = fs_devices->latest_dev->bdev;
 	s = sget(fs_type, btrfs_test_super, btrfs_set_super, flags | SB_NOSEC,
 		 fs_info);
 	if (IS_ERR(s)) {
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index bc2e4683e856..4afa050384d9 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1092,7 +1092,7 @@ void btrfs_free_extra_devids(struct btrfs_fs_devices *fs_devices)
 	list_for_each_entry(seed_dev, &fs_devices->seed_list, seed_list)
 		__btrfs_free_extra_devids(seed_dev, &latest_dev);
 
-	fs_devices->latest_bdev = latest_dev->bdev;
+	fs_devices->latest_dev = latest_dev;
 
 	mutex_unlock(&uuid_mutex);
 }
@@ -1225,7 +1225,7 @@ static int open_fs_devices(struct btrfs_fs_devices *fs_devices,
 		return -EINVAL;
 
 	fs_devices->opened = 1;
-	fs_devices->latest_bdev = latest_dev->bdev;
+	fs_devices->latest_dev = latest_dev;
 	fs_devices->total_rw_bytes = 0;
 	fs_devices->chunk_alloc_policy = BTRFS_CHUNK_ALLOC_REGULAR;
 	fs_devices->read_policy = BTRFS_READ_POLICY_PID;
@@ -1993,7 +1993,7 @@ static struct btrfs_device * btrfs_find_next_active_device(
 }
 
 /*
- * Helper function to check if the given device is part of s_bdev / latest_bdev
+ * Helper function to check if the given device is part of s_bdev / latest_dev
  * and replace it with the provided or the next active device, in the context
  * where this function called, there should be always be another device (or
  * this_dev) which is active.
@@ -2012,8 +2012,8 @@ void __cold btrfs_assign_next_active_device(struct btrfs_device *device,
 			(fs_info->sb->s_bdev == device->bdev))
 		fs_info->sb->s_bdev = next_device->bdev;
 
-	if (fs_info->fs_devices->latest_bdev == device->bdev)
-		fs_info->fs_devices->latest_bdev = next_device->bdev;
+	if (fs_info->fs_devices->latest_dev->bdev == device->bdev)
+		fs_info->fs_devices->latest_dev = next_device;
 }
 
 /*
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 2183361db614..4db10d071d67 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -246,7 +246,11 @@ struct btrfs_fs_devices {
 	/* Highest generation number of seen devices */
 	u64 latest_generation;
 
-	struct block_device *latest_bdev;
+	/*
+	 * The mount device or a device with highest generation after removal
+	 * or replace.
+	 */
+	struct btrfs_device *latest_dev;
 
 	/* all of the devices in the FS, protected by a mutex
 	 * so we can safely walk it to write out the supers without
-- 
2.33.1

[PATCH stable-5.15.y 2/4] btrfs: use latest_dev in btrfs_show_devname

[Anand Jain]

Commit 6605fd2f394bba0a0059df2b6cfc87b0b6d393a2 upstream.

The test case btrfs/238 reports the warning below:

 WARNING: CPU: 3 PID: 481 at fs/btrfs/super.c:2509 btrfs_show_devname+0x104/0x1e8 [btrfs]
 CPU: 2 PID: 1 Comm: systemd Tainted: G        W  O 5.14.0-rc1-custom #72
 Hardware name: QEMU QEMU Virtual Machine, BIOS 0.0.0 02/06/2015
 Call trace:
   btrfs_show_devname+0x108/0x1b4 [btrfs]
   show_mountinfo+0x234/0x2c4
   m_show+0x28/0x34
   seq_read_iter+0x12c/0x3c4
   vfs_read+0x29c/0x2c8
   ksys_read+0x80/0xec
   __arm64_sys_read+0x28/0x34
   invoke_syscall+0x50/0xf8
   do_el0_svc+0x88/0x138
   el0_svc+0x2c/0x8c
   el0t_64_sync_handler+0x84/0xe4
   el0t_64_sync+0x198/0x19c

Reason:
While btrfs_prepare_sprout() moves the fs_devices::devices into
fs_devices::seed_list, the btrfs_show_devname() searches for the devices
and found none, leading to the warning as in above.

Fix:
latest_dev is updated according to the changes to the device list.
That means we could use the latest_dev->name to show the device name in
/proc/self/mounts, the pointer will be always valid as it's assigned
before the device is deleted from the list in remove or replace.
The RCU protection is sufficient as the device structure is freed after
synchronization.

Reported-by: Su Yue <l@damenly.su>
Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/super.c | 24 +++++-------------------
 1 file changed, 5 insertions(+), 19 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index e4963da4dd08..7f91d62c2225 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -2463,30 +2463,16 @@ static int btrfs_unfreeze(struct super_block *sb)
 static int btrfs_show_devname(struct seq_file *m, struct dentry *root)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(root->d_sb);
-	struct btrfs_device *dev, *first_dev = NULL;
 
 	/*
-	 * Lightweight locking of the devices. We should not need
-	 * device_list_mutex here as we only read the device data and the list
-	 * is protected by RCU.  Even if a device is deleted during the list
-	 * traversals, we'll get valid data, the freeing callback will wait at
-	 * least until the rcu_read_unlock.
+	 * There should be always a valid pointer in latest_dev, it may be stale
+	 * for a short moment in case it's being deleted but still valid until
+	 * the end of RCU grace period.
 	 */
 	rcu_read_lock();
-	list_for_each_entry_rcu(dev, &fs_info->fs_devices->devices, dev_list) {
-		if (test_bit(BTRFS_DEV_STATE_MISSING, &dev->dev_state))
-			continue;
-		if (!dev->name)
-			continue;
-		if (!first_dev || dev->devid < first_dev->devid)
-			first_dev = dev;
-	}
-
-	if (first_dev)
-		seq_escape(m, rcu_str_deref(first_dev->name), " \t\n\\");
-	else
-		WARN_ON(1);
+	seq_escape(m, rcu_str_deref(fs_info->fs_devices->latest_dev->name), " \t\n\\");
 	rcu_read_unlock();
+
 	return 0;
 }
 
-- 
2.33.1

[PATCH stable-5.15.y 3/4] btrfs: update latest_dev when we create a sprout device

[Anand Jain]

Commit b7cb29e666fe79dda5dbe5f57fb7c92413bf161c upstream.

When we add a device to the seed filesystem (sprouting) it is a new
filesystem (and fsid) on the device added. Update the latest_dev so
that /proc/self/mounts shows the correct device.

Example:

  $ btrfstune -S1 /dev/vg/seed
  $ mount /dev/vg/seed /btrfs
  mount: /btrfs: WARNING: device write-protected, mounted read-only.

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

  $ btrfs dev add -f /dev/vg/new /btrfs

Before:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-seed /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

After:

  $ cat /proc/self/mounts | grep btrfs
  /dev/mapper/vg-new /btrfs btrfs ro,relatime,space_cache,subvolid=5,subvol=/ 0 0

Tested-by: Su Yue <l@damenly.su>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 4afa050384d9..b996ea0dc78b 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2634,6 +2634,8 @@ int btrfs_init_new_device(struct btrfs_fs_info *fs_info, const char *device_path
 			btrfs_abort_transaction(trans, ret);
 			goto error_trans;
 		}
+		btrfs_assign_next_active_device(fs_info->fs_devices->latest_dev,
+						device);
 	}
 
 	device->fs_devices = fs_devices;
-- 
2.33.1

[PATCH stable-5.15.y 4/4] btrfs: remove stale comment about the btrfs_show_devname

[Anand Jain]

Commit cdccc03a8a369b59cff5e7ea3292511cfa551120 upstream.

There were few lockdep warnings because btrfs_show_devname() was using
device_list_mutex as recorded in the commits:

  0ccd05285e7f ("btrfs: fix a possible umount deadlock")
  779bf3fefa83 ("btrfs: fix lock dep warning, move scratch dev out of device_list_mutex and uuid_mutex")

And finally, commit 88c14590cdd6 ("btrfs: use RCU in btrfs_show_devname
for device list traversal") removed the device_list_mutex from
btrfs_show_devname for performance reasons.

This patch removes a stale comment about the function
btrfs_show_devname and device_list_mutex.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/volumes.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index b996ea0dc78b..0f549d2681c0 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -2312,13 +2312,6 @@ void btrfs_destroy_dev_replace_tgtdev(struct btrfs_device *tgtdev)
 
 	mutex_unlock(&fs_devices->device_list_mutex);
 
-	/*
-	 * The update_dev_time() with in btrfs_scratch_superblocks()
-	 * may lead to a call to btrfs_show_devname() which will try
-	 * to hold device_list_mutex. And here this device
-	 * is already out of device list, so we don't have to hold
-	 * the device_list_mutex lock.
-	 */
 	btrfs_scratch_superblocks(tgtdev->fs_info, tgtdev->bdev,
 				  tgtdev->name->str);
 
-- 
2.33.1

Re: [PATCH stable-5.15.y 0/4] backport test case btrfs/216 fixes

[Greg KH]

On Thu, Dec 16, 2021 at 09:04:09PM +0800, Anand Jain wrote:
> In an attempt to make all the fstests test cases pass on stable-5.15.y,
> backport fixes for the test case btrfs/216.
> 
> Anand Jain (4):
>   btrfs: convert latest_bdev type to btrfs_device and rename
>   btrfs: use latest_dev in btrfs_show_devname
>   btrfs: update latest_dev when we create a sprout device
>   btrfs: remove stale comment about the btrfs_show_devname
> 
>  fs/btrfs/disk-io.c   |  6 +++---
>  fs/btrfs/extent_io.c |  2 +-
>  fs/btrfs/inode.c     |  2 +-
>  fs/btrfs/super.c     | 26 ++++++--------------------
>  fs/btrfs/volumes.c   | 19 +++++++------------
>  fs/btrfs/volumes.h   |  6 +++++-
>  6 files changed, 23 insertions(+), 38 deletions(-)
> 
> -- 
> 2.33.1
> 

Now queued up, thanks.

greg k-h