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xfs: consolidate buffer locking in xfs_buf_get_map

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Consolidate the code to lock the buffer based on the passed in flags
into xfs_buf_get_map instead of having two different sites for buffer
lookup vs insertation.  This requires initializing b_lock to unlocked on
allocation and doing an atomic for locking it for newly allocated buffers,
but greatly simplifies the logic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
This commit is contained in:
Christoph Hellwig 2026-07-15 16:50:55 +02:00 committed by Carlos Maiolino
parent 45fd506c33
commit 568c8798a3
2 changed files with 23 additions and 41 deletions
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62
fs/xfs/xfs_buf.c
View File

@ -282,15 +282,8 @@ xfs_buf_alloc(
* specifically set by later operations on the buffer.
*/
flags &= ~(XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
/*
* A new buffer is held and locked by the owner. This ensures that the
* buffer is owned by the caller and racing RCU lookups right after
* inserting into the hash table are safe (and will have to wait for
* the unlock to do anything non-trivial).
*/
lockref_init(&bp->b_lockref);
sema_init(&bp->b_sema, 0); /* held, no waiters */
sema_init(&bp->b_sema, 1); /* unlocked */
atomic_set(&bp->b_lru_ref, 1);
init_completion(&bp->b_iowait);
INIT_LIST_HEAD(&bp->b_lru);
@ -433,33 +426,25 @@ xfs_buf_find_lock(
return 0;
}
static inline int
static inline struct xfs_buf *
xfs_buf_lookup(
struct xfs_buftarg *btp,
struct xfs_buf_map *map,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
struct xfs_buf_map *map)
{
struct xfs_buf *bp;
int error;
rcu_read_lock();
bp = rhashtable_lookup(&btp->bt_hash, map, xfs_buf_hash_params);
if (!bp || !lockref_get_not_dead(&bp->b_lockref)) {
rcu_read_unlock();
return -ENOENT;
XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
return NULL;
}
rcu_read_unlock();
error = xfs_buf_find_lock(bp, flags);
if (error) {
xfs_buf_rele(bp);
return error;
}
trace_xfs_buf_find(bp, flags, _RET_IP_);
*bpp = bp;
return 0;
trace_xfs_buf_find(bp, _RET_IP_);
XFS_STATS_INC(btp->bt_mount, xb_get_locked);
return bp;
}
/*
@ -509,11 +494,7 @@ xfs_buf_find_insert(
goto retry;
}
rcu_read_unlock();
error = xfs_buf_find_lock(bp, flags);
if (error)
xfs_buf_rele(bp);
else
*bpp = bp;
*bpp = bp;
goto out_free_buf;
}
rcu_read_unlock();
@ -555,21 +536,20 @@ xfs_buf_get_map(
if (error)
return error;
error = xfs_buf_lookup(btp, &cmap, flags, &bp);
if (error && error != -ENOENT)
return error;
/* cache hits always outnumber misses by at least 10:1 */
bp = xfs_buf_lookup(btp, &cmap);
if (unlikely(!bp)) {
XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
if (flags & XBF_INCORE)
return 0;
return -ENOENT;
error = xfs_buf_find_insert(btp, &cmap, map, nmaps, flags, &bp);
if (error)
return error;
} else {
XFS_STATS_INC(btp->bt_mount, xb_get_locked);
}
error = xfs_buf_find_lock(bp, flags);
if (error) {
xfs_buf_rele(bp);
return error;
}
/*
@ -794,9 +774,11 @@ xfs_buf_get_uncached(
DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
error = xfs_buf_alloc(target, &map, 1, 0, bpp);
if (!error)
trace_xfs_buf_get_uncached(*bpp, _RET_IP_);
return error;
if (error)
return error;
xfs_buf_lock(*bpp);
trace_xfs_buf_get_uncached(*bpp, _RET_IP_);
return 0;
}
/*

2
fs/xfs/xfs_trace.h
View File

@ -792,6 +792,7 @@ DEFINE_BUF_EVENT(xfs_buf_backing_folio);
DEFINE_BUF_EVENT(xfs_buf_backing_kmem);
DEFINE_BUF_EVENT(xfs_buf_backing_vmalloc);
DEFINE_BUF_EVENT(xfs_buf_backing_fallback);
DEFINE_BUF_EVENT(xfs_buf_find);
/* not really buffer traces, but the buf provides useful information */
DEFINE_BUF_EVENT(xfs_btree_corrupt);
@ -837,7 +838,6 @@ DECLARE_EVENT_CLASS(xfs_buf_flags_class,
DEFINE_EVENT(xfs_buf_flags_class, name, \
TP_PROTO(struct xfs_buf *bp, unsigned flags, unsigned long caller_ip), \
TP_ARGS(bp, flags, caller_ip))
DEFINE_BUF_FLAGS_EVENT(xfs_buf_find);
DEFINE_BUF_FLAGS_EVENT(xfs_buf_get);
DEFINE_BUF_FLAGS_EVENT(xfs_buf_read);
DEFINE_BUF_FLAGS_EVENT(xfs_buf_readahead);