| Message ID | 1437008863-8399-1-git-send-email-kamal@canonical.com |
|---|---|
| State | New |
| Headers | show |
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c index 6f49b28..a25cb5b 100644 --- a/fs/btrfs/super.c +++ b/fs/btrfs/super.c @@ -1205,7 +1205,9 @@ static struct dentry *mount_subvol(const char *subvol_name, int flags, return ERR_CAST(mnt); } + down_write(&mnt->mnt_sb->s_umount); r = btrfs_remount(mnt->mnt_sb, &flags, NULL); + up_write(&mnt->mnt_sb->s_umount); if (r < 0) { /* FIXME: release vfsmount mnt ??*/ kfree(newargs);
This is a note to let you know that I have just added a patch titled Btrfs: lock superblock before remounting for rw subvol to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree which can be found at: http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue This patch is scheduled to be released in version 3.19.y-ckt4. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.19.y-ckt tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 787744ae823b55ca498bd3d3a3748f320ad4fcc6 Mon Sep 17 00:00:00 2001 From: Omar Sandoval <osandov@osandov.com> Date: Mon, 18 May 2015 02:16:26 -0700 Subject: Btrfs: lock superblock before remounting for rw subvol commit 773cd04ec1911abb33cf9538b65f55b76cad5d92 upstream. Since commit 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with different ro/rw options"), when mounting a subvolume read/write when another subvolume has previously been mounted read-only, we first do a remount. However, this should be done with the superblock locked, as per sync_filesystem(): /* * We need to be protected against the filesystem going from * r/o to r/w or vice versa. */ WARN_ON(!rwsem_is_locked(&sb->s_umount)); This WARN_ON can easily be hit with: mkfs.btrfs -f /dev/vdb mount /dev/vdb /mnt btrfs subvol create /mnt/vol1 btrfs subvol create /mnt/vol2 umount /mnt mount -oro,subvol=/vol1 /dev/vdb /mnt mount -orw,subvol=/vol2 /dev/vdb /mnt2 Fixes: 0723a0473fb4 ("btrfs: allow mounting btrfs subvolumes with different ro/rw options") Reviewed-by: David Sterba <dsterba@suse.cz> Signed-off-by: Omar Sandoval <osandov@osandov.com> Signed-off-by: Chris Mason <clm@fb.com> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- fs/btrfs/super.c | 2 ++ 1 file changed, 2 insertions(+) -- 1.9.1