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btrfs: don't show full path of bind mounts in subvol=

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Chris Murphy reported a problem where rpm ostree will bind mount a bunch
of things for whatever voodoo it's doing.  But when it does this
/proc/mounts shows something like

  /dev/sda /mnt/test btrfs rw,relatime,subvolid=256,subvol=/foo 0 0
  /dev/sda /mnt/test/baz btrfs rw,relatime,subvolid=256,subvol=/foo/bar 0 0

Despite subvolid=256 being subvol=/foo.  This is because we're just
spitting out the dentry of the mount point, which in the case of bind
mounts is the source path for the mountpoint.  Instead we should spit
out the path to the actual subvol.  Fix this by looking up the name for
the subvolid we have mounted.  With this fix the same test looks like
this

  /dev/sda /mnt/test btrfs rw,relatime,subvolid=256,subvol=/foo 0 0
  /dev/sda /mnt/test/baz btrfs rw,relatime,subvolid=256,subvol=/foo 0 0

Reported-by: Chris Murphy <chris@colorremedies.com>
CC: stable@vger.kernel.org # 4.4+
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2020-07-22 11:12:46 -04:00 committed by David Sterba
parent 27942c9971
commit 3ef3959b29
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/btrfs/super.c
View File

@ -1386,6 +1386,7 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
{
struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
const char *compress_type;
const char *subvol_name;
if (btrfs_test_opt(info, DEGRADED))
seq_puts(seq, ",degraded");
@ -1472,8 +1473,13 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
seq_puts(seq, ",ref_verify");
seq_printf(seq, ",subvolid=%llu",
BTRFS_I(d_inode(dentry))->root->root_key.objectid);
seq_puts(seq, ",subvol=");
seq_dentry(seq, dentry, " \t\n\\");
subvol_name = btrfs_get_subvol_name_from_objectid(info,
BTRFS_I(d_inode(dentry))->root->root_key.objectid);
if (!IS_ERR(subvol_name)) {
seq_puts(seq, ",subvol=");
seq_escape(seq, subvol_name, " \t\n\\");
kfree(subvol_name);
}
return 0;
}