On Tue, Aug 10, 2021 at 05:46:32PM -0700, Darrick J. Wong wrote:

On Tue, Aug 10, 2021 at 03:28:51PM +1000, Dave Chinner wrote:

quoted

From: Dave Chinner <redacted>

TO stop external users from using b_bn as the disk address of the
buffer, rename it to b_index to indicate that it is the buffer cache
index, not the block number of the buffer. Code that needs the disk
address should use xfs_buf_daddr() to obtain it.

Do the rename and clean up any of the remaining b_bn cruft that is
left over and is now unused.

Signed-off-by: Dave Chinner <redacted>
---
 fs/xfs/xfs_buf.c | 19 +++++++++++--------
 fs/xfs/xfs_buf.h | 18 +-----------------
 2 files changed, 12 insertions(+), 25 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index c1bb6e41595b..6f6c6937baaa 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c

@@ -251,7 +251,7 @@ _xfs_buf_alloc(
 		return error;
 	}
 
-	bp->b_bn = map[0].bm_bn;
+	bp->b_index = map[0].bm_bn;
 	bp->b_length = 0;
 	for (i = 0; i < nmaps; i++) {
 		bp->b_maps[i].bm_bn = map[i].bm_bn;

@@ -459,7 +459,7 @@ _xfs_buf_obj_cmp(
 	 */
 	BUILD_BUG_ON(offsetof(struct xfs_buf_map, bm_bn) != 0);
 
-	if (bp->b_bn != map->bm_bn)
+	if (bp->b_index != map->bm_bn)
 		return 1;
 
 	if (unlikely(bp->b_length != map->bm_len)) {

@@ -481,7 +481,7 @@ static const struct rhashtable_params xfs_buf_hash_params = {
 	.min_size		= 32,	/* empty AGs have minimal footprint */
 	.nelem_hint		= 16,
 	.key_len		= sizeof(xfs_daddr_t),
-	.key_offset		= offsetof(struct xfs_buf, b_bn),
+	.key_offset		= offsetof(struct xfs_buf, b_index),

I would've called this field b_rhash_key, since "index" is a kind of
vague.

Ok.

quoted

@@ -875,7 +877,7 @@ xfs_buf_read_uncached(
 
 	/* set up the buffer for a read IO */
 	ASSERT(bp->b_map_count == 1);
-	bp->b_bn = XFS_BUF_DADDR_NULL;  /* always null for uncached buffers */
+	bp->b_index = XFS_BUF_DADDR_NULL;
 	bp->b_maps[0].bm_bn = daddr;
 	bp->b_flags |= XBF_READ;
 	bp->b_ops = ops;

@@ -1513,7 +1515,7 @@ _xfs_buf_ioapply(
 						   SHUTDOWN_CORRUPT_INCORE);
 				return;
 			}
-		} else if (bp->b_bn != XFS_BUF_DADDR_NULL) {
+		} else if (bp->b_index != XFS_BUF_DADDR_NULL) {
 			struct xfs_mount *mp = bp->b_mount;
 
 			/*

@@ -1523,7 +1525,8 @@ _xfs_buf_ioapply(
 			if (xfs_has_crc(mp)) {
 				xfs_warn(mp,
 					"%s: no buf ops on daddr 0x%llx len %d",
-					__func__, bp->b_bn, bp->b_length);
+					__func__, xfs_buf_daddr(bp),
+					bp->b_length);
 				xfs_hex_dump(bp->b_addr,
 						XFS_CORRUPTION_DUMP_LEN);
 				dump_stack();

@@ -1793,7 +1796,7 @@ xfs_buftarg_drain(
 				xfs_buf_alert_ratelimited(bp,
 					"XFS: Corruption Alert",
 "Corruption Alert: Buffer at daddr 0x%llx had permanent write failures!",
-					(long long)bp->b_bn);
+					(long long)xfs_buf_daddr(bp));

These belong in the previous patch, right?

Depends on your POV. This patch cleans up all the internal (mis)uses of
b_bn, while the previous patches addressed all the external uses.
The mods could be in either, I just chose to split internal/external
modification based on the file rather than on the specific (ab)use
being corrected....

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com