xfs: merge xfs_buf_find() and xfs_buf_get_map()

Now that we factored xfs_buf_find(), we can start separating into
distinct fast and slow paths from xfs_buf_get_map(). We start by
moving the lookup map and perag setup to _get_map(), and then move
all the specifics of the fast path lookup into xfs_buf_lookup()
and call it directly from _get_map(). We the move all the slow path
code to xfs_buf_find_insert(), which is now also called directly
from _get_map(). As such, xfs_buf_find() now goes away.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
This commit is contained in:
Dave Chinner 2022-07-14 12:04:31 +10:00 committed by Dave Chinner
parent de67dc5754
commit 348000804a

View File

@ -537,7 +537,6 @@ xfs_buf_find_lock(
if (!xfs_buf_trylock(bp)) {
if (flags & XBF_TRYLOCK) {
XFS_STATS_INC(bp->b_mount, xb_busy_locked);
xfs_buf_rele(bp);
return -EAGAIN;
}
xfs_buf_lock(bp);
@ -557,144 +556,57 @@ xfs_buf_find_lock(
return 0;
}
static inline struct xfs_buf *
static inline int
xfs_buf_lookup(
struct xfs_perag *pag,
struct xfs_buf_map *map)
struct xfs_buf_map *map,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
{
struct xfs_buf *bp;
int error;
spin_lock(&pag->pag_buf_lock);
bp = rhashtable_lookup(&pag->pag_buf_hash, map, xfs_buf_hash_params);
if (!bp)
return NULL;
if (!bp) {
spin_unlock(&pag->pag_buf_lock);
return -ENOENT;
}
atomic_inc(&bp->b_hold);
return bp;
spin_unlock(&pag->pag_buf_lock);
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;
}
/*
* Insert the new_bp into the hash table. This consumes the perag reference
* taken for the lookup.
* taken for the lookup regardless of the result of the insert.
*/
static int
xfs_buf_find_insert(
struct xfs_buftarg *btp,
struct xfs_perag *pag,
struct xfs_buf *new_bp)
{
/* No match found */
if (!new_bp) {
xfs_perag_put(pag);
XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
return -ENOENT;
}
/* the buffer keeps the perag reference until it is freed */
new_bp->b_pag = pag;
rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
xfs_buf_hash_params);
return 0;
}
/*
* Look up a buffer in the buffer cache and return it referenced and locked
* in @found_bp.
*
* If @new_bp is supplied and we have a lookup miss, insert @new_bp into the
* cache.
*
* If XBF_TRYLOCK is set in @flags, only try to lock the buffer and return
* -EAGAIN if we fail to lock it.
*
* Return values are:
* -EFSCORRUPTED if have been supplied with an invalid address
* -EAGAIN on trylock failure
* -ENOENT if we fail to find a match and @new_bp was NULL
* 0, with @found_bp:
* - @new_bp if we inserted it into the cache
* - the buffer we found and locked.
*/
static int
xfs_buf_find(
struct xfs_buftarg *btp,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf *new_bp,
struct xfs_buf **found_bp)
{
struct xfs_perag *pag;
struct xfs_buf *bp;
struct xfs_buf_map cmap = { .bm_bn = map[0].bm_bn };
int error;
int i;
*found_bp = NULL;
for (i = 0; i < nmaps; i++)
cmap.bm_len += map[i].bm_len;
error = xfs_buf_map_verify(btp, &cmap);
if (error)
return error;
pag = xfs_perag_get(btp->bt_mount,
xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
spin_lock(&pag->pag_buf_lock);
bp = xfs_buf_lookup(pag, &cmap);
if (bp)
goto found;
error = xfs_buf_find_insert(btp, pag, new_bp);
spin_unlock(&pag->pag_buf_lock);
if (error)
return error;
*found_bp = new_bp;
return 0;
found:
spin_unlock(&pag->pag_buf_lock);
xfs_perag_put(pag);
error = xfs_buf_find_lock(bp, flags);
if (error)
return error;
trace_xfs_buf_find(bp, flags, _RET_IP_);
XFS_STATS_INC(btp->bt_mount, xb_get_locked);
*found_bp = bp;
return 0;
}
/*
* Assembles a buffer covering the specified range. The code is optimised for
* cache hits, as metadata intensive workloads will see 3 orders of magnitude
* more hits than misses.
*/
int
xfs_buf_get_map(
struct xfs_buftarg *target,
struct xfs_buf_map *cmap,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
{
struct xfs_buf *bp;
struct xfs_buf *new_bp;
struct xfs_buf *bp;
int error;
*bpp = NULL;
error = xfs_buf_find(target, map, nmaps, flags, NULL, &bp);
if (!error)
goto found;
if (error != -ENOENT)
return error;
if (flags & XBF_INCORE)
return -ENOENT;
error = _xfs_buf_alloc(target, map, nmaps, flags, &new_bp);
error = _xfs_buf_alloc(btp, map, nmaps, flags, &new_bp);
if (error)
return error;
goto out_drop_pag;
/*
* For buffers that fit entirely within a single page, first attempt to
@ -709,18 +621,89 @@ xfs_buf_get_map(
goto out_free_buf;
}
error = xfs_buf_find(target, map, nmaps, flags, new_bp, &bp);
if (error)
spin_lock(&pag->pag_buf_lock);
bp = rhashtable_lookup(&pag->pag_buf_hash, cmap, xfs_buf_hash_params);
if (bp) {
atomic_inc(&bp->b_hold);
spin_unlock(&pag->pag_buf_lock);
error = xfs_buf_find_lock(bp, flags);
if (error)
xfs_buf_rele(bp);
else
*bpp = bp;
goto out_free_buf;
}
if (bp != new_bp)
xfs_buf_free(new_bp);
/* The buffer keeps the perag reference until it is freed. */
new_bp->b_pag = pag;
rhashtable_insert_fast(&pag->pag_buf_hash, &new_bp->b_rhash_head,
xfs_buf_hash_params);
spin_unlock(&pag->pag_buf_lock);
*bpp = new_bp;
return 0;
found:
out_free_buf:
xfs_buf_free(new_bp);
out_drop_pag:
xfs_perag_put(pag);
return error;
}
/*
* Assembles a buffer covering the specified range. The code is optimised for
* cache hits, as metadata intensive workloads will see 3 orders of magnitude
* more hits than misses.
*/
int
xfs_buf_get_map(
struct xfs_buftarg *btp,
struct xfs_buf_map *map,
int nmaps,
xfs_buf_flags_t flags,
struct xfs_buf **bpp)
{
struct xfs_perag *pag;
struct xfs_buf *bp = NULL;
struct xfs_buf_map cmap = { .bm_bn = map[0].bm_bn };
int error;
int i;
for (i = 0; i < nmaps; i++)
cmap.bm_len += map[i].bm_len;
error = xfs_buf_map_verify(btp, &cmap);
if (error)
return error;
pag = xfs_perag_get(btp->bt_mount,
xfs_daddr_to_agno(btp->bt_mount, cmap.bm_bn));
error = xfs_buf_lookup(pag, &cmap, flags, &bp);
if (error && error != -ENOENT)
goto out_put_perag;
/* cache hits always outnumber misses by at least 10:1 */
if (unlikely(!bp)) {
XFS_STATS_INC(btp->bt_mount, xb_miss_locked);
if (flags & XBF_INCORE)
goto out_put_perag;
/* xfs_buf_find_insert() consumes the perag reference. */
error = xfs_buf_find_insert(btp, pag, &cmap, map, nmaps,
flags, &bp);
if (error)
return error;
} else {
XFS_STATS_INC(btp->bt_mount, xb_get_locked);
xfs_perag_put(pag);
}
/* We do not hold a perag reference anymore. */
if (!bp->b_addr) {
error = _xfs_buf_map_pages(bp, flags);
if (unlikely(error)) {
xfs_warn_ratelimited(target->bt_mount,
xfs_warn_ratelimited(btp->bt_mount,
"%s: failed to map %u pages", __func__,
bp->b_page_count);
xfs_buf_relse(bp);
@ -735,12 +718,13 @@ found:
if (!(flags & XBF_READ))
xfs_buf_ioerror(bp, 0);
XFS_STATS_INC(target->bt_mount, xb_get);
XFS_STATS_INC(btp->bt_mount, xb_get);
trace_xfs_buf_get(bp, flags, _RET_IP_);
*bpp = bp;
return 0;
out_free_buf:
xfs_buf_free(new_bp);
out_put_perag:
xfs_perag_put(pag);
return error;
}