On 02/27/2018 10:47 PM, Eric Sandeen wrote:

On 2/27/18 4:44 AM, Yang Joseph wrote:

quoted

xfs_repair should not touch non-xfs mountpoints in platform_check_mount().
If non-xfs mountpoints can be filtered out, the dead fuse mountpoint can
never block our xfs_repair. The following patch can fix my problem and not
add dangerous option to xfs_repair.

I don't think this is a safe solution.  For example:

# mkfs.ext4 /dev/sdb1
# mount /dev/sdb1 /mnt/test

Old behavior:

# xfs_repair /dev/sdb1
xfs_repair: /dev/sdb1 contains a mounted filesystem

New behavior with your patch:

# repair/xfs_repair /dev/sdb1
xfs_repair: cannot open /dev/sdb1: Device or resource busy

As /dev/sdb1 will never be modified, I think this behavior is acceptable.

With your patch, if we explicitly ask xfs_repair to repair a non-xfs
filesystem which is mounted, it will get past all of the checks and
try to open the device O_EXCL - which should fail if the device is
mounted, but I'm guessing your fuse case would now simply hang here
instead.

Worse, other utilities aren't so graceful.

Old:

# xfs_copy /dev/sdb2 /dev/sdb1
xfs_copy:  a filesystem is mounted on target device "/dev/sdb1".
xfs_copy cannot copy to mounted filesystems.  Aborting

New:

copy/xfs_copy /dev/sdb2 /dev/sdb1
  0%  ... 10%  ... 20%  ... 30%  ... 40%  ... 50%  ... 60%  ... 70%  ... 80%  ... 90%  ... 100%

All copies completed.

(now we've just written over a mounted, writable ext4 filesystem)

This is horrible. Maybe we can add O_EXCL flag when open target device.

   //copy/xfs_copy.c:main()
   /* now open targets */

   open_flags = O_RDWR | O_EXCL; // add O_EXCL

#mount
...
/dev/sdf1 on /root/xx1 type ext4 (rw,relatime,data=ordered)
// /dev/sdf2 contains a xfs image
# ./xfs_copy.new /dev/sdf2 /dev/sdf1
xfs_copy.new:  couldn't open target "/dev/sdf1"
Aborting XFS copy - reason:  Device or resource busy

(Anyone want to investigate whether every device open in xfsprogs should
be O_EXCL?)

// from manpage: OPEN(2)
on Linux 2.6
               and later, O_EXCL can be used without O_CREAT if pathname 
refers to a block device.  If the block device is  in  use
               by the system (e.g., mounted), open() fails with the 
error EBUSY.

Also, in general:

When sending a patch to the list, please prefix the subject with
[PATCH] to make it obvious; patches also require a Signed-off-by:
line similar to:

   Signed-off-by: Yang Joseph [off-list ref]

The Signed-off-by: tag indicates that the signer was involved in the
development of the patch.

It essentially states that you are the author of this work and you have
the right to submit it for inclusion in this project.

ok, thank you.

Thanks,
-Eric

quoted

thx,

Yang Honggang

-------------------------new patch----------------------

diff --git a/libxfs/linux.c b/libxfs/linux.c
index 0bace3e..6ad24ce 100644
--- a/libxfs/linux.c
+++ b/libxfs/linux.c

@@ -44,6 +44,7 @@ static int max_block_alignment;
  #endif

  #define PROC_MOUNTED   "/proc/mounts"
+#define MNTTYPE_XFS        "xfs"

indentation should be consistent with the string above; the whole
patch is whitespace-mangled and won't apply.

quoted

  /*
   * Check if the filesystem is mounted.  Be verbose if asked, and

@@ -78,6 +79,9 @@ platform_check_mount(char *name, char *block, struct stat *s, int flags)
                 return 1;
         }
         while ((mnt = getmntent(f)) != NULL) {
+               /* filter out non xfs mountpoint */
+               if (strncmp(mnt->mnt_type, MNTTYPE_XFS, strlen(mnt->mnt_type)))
+                       continue;
                 if (stat(mnt->mnt_dir, &mst) < 0)
                         continue;
                 if (mst.st_dev != s->st_rdev)
-------------------------new patch end-----------------

On 02/25/2018 06:04 AM, Dave Chinner wrote:

quoted

On Sat, Feb 24, 2018 at 11:56:44AM -0600, Eric Sandeen wrote:

quoted

On 2/24/18 5:23 AM, Yang Joseph wrote:

quoted

hello,

Before the repair process, xfs_repair will check if user specified device already
has a writable mountpoint. And it will stat all the mountpoints of the system. If there
is a dead mountpoint, this checking will be blocked and xfs_repair will enter 'D' state.

So why is the mount point dead?

That kinda means that the filesystem is still mounted, but something
has hung somewhere and the filesystem may still have active
references to the underlying device and be doing stuff that is
modifying the filesystem....

And if the device is still busy, then you aren't going to be able to
mount the repaired device, anyway, because the block device is still
busy...

quoted

That sounds like a bug worth fixing, but I am much
less excited about adding options which could do serious damage
to a filesystem.

TO me it sounds like something that should be fixed by a reboot, not
by adding dangerous options to xfs_repair...

Cheers,

Dave.

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