On Wed, May 02, 2018 at 02:56:22PM -0500, Eric Sandeen wrote:
> After we lost ustat(2) in commit 4e7a824, we ended up with a slightly
> bonkers method to determine if our target block device was mounted:
> it goes through every entry returned by getmntent and stats the dir
> to see if its underlying device matches ours.
>
> Unfortunately that dir might be a hung nfs server and sadness ensues.
>
> So do some pre-checks; can we stat the mounted "device?" If so is
> it really a block device? If not, skip it.
>
> Fixes: 4e7a824 ("libxfs/linux.c: Replace use of ustat by stat")
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
Looks ok,
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
--D
> ---
>
> diff --git a/libxfs/linux.c b/libxfs/linux.c
> index 0bace3e..7350fa7 100644
> --- a/libxfs/linux.c
> +++ b/libxfs/linux.c
> @@ -77,7 +77,21 @@ platform_check_mount(char *name, char *block, struct stat *s, int flags)
> progname, name);
> return 1;
> }
> + /*
> + * This whole business is to work out if our block device is mounted
> + * after we lost ustat(2), see:
> + * 4e7a824 libxfs/linux.c: Replace use of ustat by stat
> + * We don't really want to stat every single mounted directory,
> + * as that may include tmpfs, cgroups, procfs or - worst - hung nfs
> + * servers. So we check the "device" before going after the mountpoint.
> + */
> while ((mnt = getmntent(f)) != NULL) {
> + /* If the "fsname" is't a stat-able device, skip it */
> + if (stat(mnt->mnt_fsname, &mst) < 0)
> + continue;
> + if (!S_ISBLK(mst.st_mode))
> + continue;
> + /* Ok, this entry does seem to be a mounted block device */
> if (stat(mnt->mnt_dir, &mst) < 0)
> continue;
> if (mst.st_dev != s->st_rdev)
>
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