xfs: fix regression in "cleanup xfs_dir2_block_getdents"

Commit 263dde869bd09 ("xfs: cleanup xfs_dir2_block_getdents") introduced
a getdents regression, when it converted the pointer arithmetics to
offset calculations: offset is updated in the loop already for the next
iteration, but the updated offset value is used incorrectly in two
places, where we should have used the not-yet-updated value.

This caused for example "git clean -ffdx" failures to cleanup certain
directory structures when running in a container.

Fix the regression by making sure we use proper offset in the loop body.
Thanks to Christoph Hellwig for suggestion how to best fix the code.

Cc: Christoph Hellwig <hch@lst.de>
Fixes: 263dde869bd09 ("xfs: cleanup xfs_dir2_block_getdents")
Signed-off-by: Tommi Rantala <tommi.t.rantala@nokia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>

diff --git a/fs/xfs/xfs_dir2_readdir.c b/fs/xfs/xfs_dir2_readdir.c
index 0d3b640..871ec22 100644 (file)
--- a/fs/xfs/xfs_dir2_readdir.c
+++ b/fs/xfs/xfs_dir2_readdir.c
@@ -147,7 +147,7 @@ xfs_dir2_block_getdents(
        xfs_off_t               cook;
        struct xfs_da_geometry  *geo = args->geo;
        int                     lock_mode;
-       unsigned int            offset;
+       unsigned int            offset, next_offset;
        unsigned int            end;
 
        /*
@@ -173,9 +173,10 @@ xfs_dir2_block_getdents(
         * Loop over the data portion of the block.
         * Each object is a real entry (dep) or an unused one (dup).
         */
-       offset = geo->data_entry_offset;
        end = xfs_dir3_data_end_offset(geo, bp->b_addr);
-       while (offset < end) {
+       for (offset = geo->data_entry_offset;
+            offset < end;
+            offset = next_offset) {
                struct xfs_dir2_data_unused     *dup = bp->b_addr + offset;
                struct xfs_dir2_data_entry      *dep = bp->b_addr + offset;
                uint8_t filetype;
@@ -184,14 +185,15 @@ xfs_dir2_block_getdents(
                 * Unused, skip it.
                 */
                if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
-                       offset += be16_to_cpu(dup->length);
+                       next_offset = offset + be16_to_cpu(dup->length);
                        continue;
                }
 
                /*
                 * Bump pointer for the next iteration.
                 */
-               offset += xfs_dir2_data_entsize(dp->i_mount, dep->namelen);
+               next_offset = offset +
+                       xfs_dir2_data_entsize(dp->i_mount, dep->namelen);
 
                /*
                 * The entry is before the desired starting point, skip it.