[PATCH 11/45] xfs: xfs_buf_item_size_segment() needs to pass segment offset

Dave Chinner
2021-03-05T05:12:00Z

From: Dave Chinner <dchinner@redhat.com>

Otherwise it doesn't correctly calculate the number of vectors
in a logged buffer that has a contiguous map that gets split into
multiple regions because the range spans discontigous memory.

Probably never been hit in practice - we don't log contiguous ranges
on unmapped buffers (inode clusters).

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
---
fs/xfs/xfs_buf_item.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 0628a65d9c55..91dc7d8c9739 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -55,6 +55,18 @@ xfs_buf_log_format_size(
(blfp->blf_map_size * sizeof(blfp->blf_data_map[0]));
}

+static inline bool
+xfs_buf_item_straddle(
+ struct xfs_buf *bp,
+ uint offset,
+ int next_bit,
+ int last_bit)
+{
+ return xfs_buf_offset(bp, offset + (next_bit << XFS_BLF_SHIFT)) !=
+ (xfs_buf_offset(bp, offset + (last_bit << XFS_BLF_SHIFT)) +
+ XFS_BLF_CHUNK);
+}
+
/*
* Return the number of log iovecs and space needed to log the given buf log
* item segment.
@@ -67,6 +79,7 @@ STATIC void
xfs_buf_item_size_segment(
struct xfs_buf_log_item *bip,
struct xfs_buf_log_format *blfp,
+ uint offset,
int *nvecs,
int *nbytes)
{
@@ -101,12 +114,8 @@ xfs_buf_item_size_segment(
*/
if (next_bit == -1) {
break;
- } else if (next_bit != last_bit + 1) {
- last_bit = next_bit;
- (*nvecs)++;
- } else if (xfs_buf_offset(bp, next_bit * XFS_BLF_CHUNK) !=
- (xfs_buf_offset(bp, last_bit * XFS_BLF_CHUNK) +
- XFS_BLF_CHUNK)) {
+ } else if (next_bit != last_bit + 1 ||
+ xfs_buf_item_straddle(bp, offset, next_bit, last_bit)) {
last_bit = next_bit;
(*nvecs)++;
} else {
@@ -141,8 +150,10 @@ xfs_buf_item_size(
int *nbytes)
{
struct xfs_buf_log_item *bip = BUF_ITEM(lip);
+ struct xfs_buf *bp = bip->bli_buf;
int i;
int bytes;
+ uint offset = 0;

ASSERT(atomic_read(&bip->bli_refcount) > 0);
if (bip->bli_flags & XFS_BLI_STALE) {
@@ -184,8 +195,9 @@ xfs_buf_item_size(
*/
bytes = 0;
for (i = 0; i < bip->bli_format_count; i++) {
- xfs_buf_item_size_segment(bip, &bip->bli_formats[i],
+ xfs_buf_item_size_segment(bip, &bip->bli_formats[i], offset,
nvecs, &bytes);
+ offset += BBTOB(bp->b_maps[i].bm_len);
}

/*
@@ -212,18 +224,6 @@ xfs_buf_item_copy_iovec(
nbits * XFS_BLF_CHUNK);
}

-static inline bool
-xfs_buf_item_straddle(
- struct xfs_buf *bp,
- uint offset,
- int next_bit,
- int last_bit)
-{
- return xfs_buf_offset(bp, offset + (next_bit << XFS_BLF_SHIFT)) !=
- (xfs_buf_offset(bp, offset + (last_bit << XFS_BLF_SHIFT)) +
- XFS_BLF_CHUNK);
-}
-
static void
xfs_buf_item_format_segment(
struct xfs_buf_log_item *bip,
--
2.28.0