xfs: fix overlapping extents returned for pNFS LAYOUTGET

xfs_fs_map_blocks() currently passes XFS_BMAPI_ENTIRE to xfs_bmapi_read(),
which causes the bmap code to expand the mapping to cover the entire
extent rather than the requested range.

A single LAYOUTGET request from the client can cause the server to
issue multiple calls to xfs_fs_map_blocks() for different offsets
within the same extent. Because the use of XFS_BMAPI_ENTIRE flag,
these calls can produce overlapping mappings.

As a result, the LAYOUTGET reply sent to the NFS client may contain
overlapping extents. This creates ambiguity in extent selection for a
given file range, which can lead to incorrect device selection,
inconsistent handling of datastate, and ultimately data corruption or
protocol violations on the client side.

Problem discovered with xfstest generic/075 test using NFSv4.2 mount
with SCSI layout.

Fix this by replacing the XFS_BMAPI_ENTIRE flag with '0' so that
xfs_bmapi_read() returns only the mapping for the requested range.

Fixes: cc6c40e09d7b1 ("NFSD/blocklayout: Support multiple extents per LAYOUTGET").
Signed-off-by: Dai Ngo <dai.ngo@oracle.com>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/fs/xfs/xfs_pnfs.c b/fs/xfs/xfs_pnfs.c
index b792e066b403dbfdad7c49ff0fa0d136073ea70e..d92993367ab649bb976bc7e86e283af13781a770 100644 (file)
--- a/fs/xfs/xfs_pnfs.c
+++ b/fs/xfs/xfs_pnfs.c
@@ -118,7 +118,6 @@ xfs_fs_map_blocks(
        struct xfs_bmbt_irec    imap;
        xfs_fileoff_t           offset_fsb, end_fsb;
        loff_t                  limit;
-       int                     bmapi_flags = XFS_BMAPI_ENTIRE;
        int                     nimaps = 1;
        uint                    lock_flags;
        int                     error = 0;
@@ -172,8 +171,9 @@ xfs_fs_map_blocks(
        offset_fsb = XFS_B_TO_FSBT(mp, offset);
 
        lock_flags = xfs_ilock_data_map_shared(ip);
+       /* request mappings for the specified range only */
        error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
-                               &imap, &nimaps, bmapi_flags);
+                               &imap, &nimaps, 0);
        if (error) {
                xfs_iunlock(ip, lock_flags);
                goto out_unlock;