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ceph: don't allow copy_file_range when stripe_count != 1

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copy_file_range tries to use the OSD 'copy-from' operation, which simply
performs a full object copy.  Unfortunately, the implementation of this
system call assumes that stripe_count is always set to 1 and doesn't take
into account that the data may be striped across an object set.  If the
file layout has stripe_count different from 1, then the destination file
data will be corrupted.

For example:

Consider a 8 MiB file with 4 MiB object size, stripe_count of 2 and
stripe_size of 2 MiB; the first half of the file will be filled with 'A's
and the second half will be filled with 'B's:

               0      4M     8M       Obj1     Obj2
               +------+------+       +----+   +----+
        file:  | AAAA | BBBB |       | AA |   | AA |
               +------+------+       |----|   |----|
                                     | BB |   | BB |
                                     +----+   +----+

If we copy_file_range this file into a new file (which needs to have the
same file layout!), then it will start by copying the object starting at
file offset 0 (Obj1).  And then it will copy the object starting at file
offset 4M -- which is Obj1 again.

Unfortunately, the solution for this is to not allow remote object copies
to be performed when the file layout stripe_count is not 1 and simply
fallback to the default (VFS) copy_file_range implementation.

Cc: stable@vger.kernel.org
Signed-off-by: Luis Henriques <lhenriques@suse.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
This commit is contained in:
Luis Henriques 2019-10-31 11:49:39 +00:00 committed by Ilya Dryomov
parent 5bb5e6ee6f
commit a3a0819388
1 changed files with 10 additions and 2 deletions
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12
fs/ceph/file.c
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@ -1959,10 +1959,18 @@ static ssize_t __ceph_copy_file_range(struct file *src_file, loff_t src_off,
if (ceph_test_mount_opt(src_fsc, NOCOPYFROM))
return -EOPNOTSUPP;
/*
* Striped file layouts require that we copy partial objects, but the
* OSD copy-from operation only supports full-object copies. Limit
* this to non-striped file layouts for now.
*/
if ((src_ci->i_layout.stripe_unit != dst_ci->i_layout.stripe_unit) ||
(src_ci->i_layout.stripe_count != dst_ci->i_layout.stripe_count) ||
(src_ci->i_layout.object_size != dst_ci->i_layout.object_size))
(src_ci->i_layout.stripe_count != 1) ||
(dst_ci->i_layout.stripe_count != 1) ||
(src_ci->i_layout.object_size != dst_ci->i_layout.object_size)) {
dout("Invalid src/dst files layout\n");
return -EOPNOTSUPP;
}
if (len < src_ci->i_layout.object_size)
return -EOPNOTSUPP; /* no remote copy will be done */