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xfs: use WRITE_ONCE to update b_flags

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Prepare for limited lockless reading of flags by using WRITE_ONCE to
prevent the compiler from doing non-standard read-modify-write
operations.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
This commit is contained in:
Christoph Hellwig 2026-07-15 16:51:00 +02:00 committed by Carlos Maiolino
parent 9f224de410
commit b15f6520ab
1 changed files with 51 additions and 35 deletions
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86
fs/xfs/xfs_buf.c
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@ -55,11 +55,27 @@ static inline bool xfs_buf_is_uncached(struct xfs_buf *bp)
return bp->b_rhash_key == XFS_BUF_DADDR_NULL;
}
static inline void
xfs_buf_set_flags(
struct xfs_buf *bp,
unsigned int flags)
{
WRITE_ONCE(bp->b_flags, bp->b_flags | flags);
}
static inline void
xfs_buf_clear_flags(
struct xfs_buf *bp,
unsigned int flags)
{
WRITE_ONCE(bp->b_flags, bp->b_flags & ~flags);
}
void
xfs_buf_set_uptodate(
struct xfs_buf *bp)
{
bp->b_flags |= XBF_DONE;
xfs_buf_set_flags(bp, XBF_DONE);
}
/*
@ -76,14 +92,14 @@ xfs_buf_stale(
{
ASSERT(xfs_buf_islocked(bp));
bp->b_flags |= XBF_STALE;
xfs_buf_set_flags(bp, XBF_STALE);
/*
* Clear the delwri status so that a delwri queue walker will not
* flush this buffer to disk now that it is stale. The delwri queue has
* a reference to the buffer, so this is safe to do.
*/
bp->b_flags &= ~_XBF_DELWRI_Q;
xfs_buf_clear_flags(bp, _XBF_DELWRI_Q);
spin_lock(&bp->b_lockref.lock);
atomic_set(&bp->b_lru_ref, 0);
@ -97,8 +113,7 @@ xfs_buf_clear_stale(
struct xfs_buf *bp)
{
ASSERT(bp->b_flags & XBF_STALE);
bp->b_flags &= ~XBF_STALE;
xfs_buf_clear_flags(bp, XBF_STALE);
}
static void
@ -175,7 +190,7 @@ xfs_buf_alloc_kmem(
bp->b_addr = NULL;
return -ENOMEM;
}
bp->b_flags |= _XBF_KMEM;
xfs_buf_set_flags(bp, _XBF_KMEM);
trace_xfs_buf_backing_kmem(bp, _RET_IP_);
return 0;
}
@ -307,7 +322,7 @@ xfs_buf_alloc(
INIT_LIST_HEAD(&bp->b_li_list);
bp->b_target = target;
bp->b_mount = target->bt_mount;
bp->b_flags = flags;
WRITE_ONCE(bp->b_flags, flags);
bp->b_rhash_key = map[0].bm_bn;
bp->b_length = 0;
bp->b_map_count = nmaps;
@ -436,7 +451,7 @@ xfs_buf_find_lock(
return -ENOENT;
}
ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
bp->b_flags &= _XBF_KMEM;
xfs_buf_clear_flags(bp, ~_XBF_KMEM);
bp->b_ops = NULL;
}
return 0;
@ -604,8 +619,9 @@ _xfs_buf_read(
{
ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD | XBF_DONE);
bp->b_flags |= XBF_READ;
xfs_buf_clear_flags(bp, XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD |
XBF_DONE);
xfs_buf_set_flags(bp, XBF_READ);
xfs_buf_submit(bp);
return xfs_buf_iowait(bp);
}
@ -641,7 +657,7 @@ xfs_buf_reverify(
bp->b_ops = ops;
bp->b_ops->verify_read(bp);
if (bp->b_error)
bp->b_flags &= ~XBF_DONE;
xfs_buf_clear_flags(bp, XBF_DONE);
return bp->b_error;
}
@ -679,7 +695,7 @@ xfs_buf_read_map(
error = xfs_buf_reverify(bp, ops);
/* We do not want read in the flags */
bp->b_flags &= ~XBF_READ;
xfs_buf_clear_flags(bp, XBF_READ);
ASSERT(bp->b_ops != NULL || ops == NULL);
}
@ -704,7 +720,7 @@ xfs_buf_read_map(
if (!xlog_is_shutdown(target->bt_mount->m_log))
xfs_buf_ioerror_alert(bp, fa);
bp->b_flags &= ~XBF_DONE;
xfs_buf_clear_flags(bp, XBF_DONE);
xfs_buf_stale(bp);
xfs_buf_relse(bp);
@ -750,8 +766,8 @@ xfs_buf_readahead_map(
}
XFS_STATS_INC(target->bt_mount, xb_get_read);
bp->b_ops = ops;
bp->b_flags &= ~(XBF_WRITE | XBF_DONE);
bp->b_flags |= flags;
xfs_buf_clear_flags(bp, XBF_WRITE | XBF_DONE);
xfs_buf_set_flags(bp, flags);
percpu_counter_inc(&target->bt_readahead_count);
xfs_buf_submit(bp);
}
@ -783,7 +799,7 @@ xfs_buf_read_uncached(
ASSERT(bp->b_map_count == 1);
bp->b_rhash_key = XFS_BUF_DADDR_NULL;
bp->b_maps[0].bm_bn = daddr;
bp->b_flags |= XBF_READ;
xfs_buf_set_flags(bp, XBF_READ);
bp->b_ops = ops;
xfs_buf_submit(bp);
@ -1077,14 +1093,14 @@ xfs_buf_ioend_handle_error(
resubmit:
xfs_buf_ioerror(bp, 0);
bp->b_flags |= (XBF_DONE | XBF_WRITE_FAIL);
xfs_buf_set_flags(bp, XBF_DONE | XBF_WRITE_FAIL);
reinit_completion(&bp->b_iowait);
xfs_buf_submit(bp);
return true;
out_stale:
xfs_buf_stale(bp);
bp->b_flags |= XBF_DONE;
bp->b_flags &= ~XBF_WRITE;
xfs_buf_set_flags(bp, XBF_DONE);
xfs_buf_clear_flags(bp, XBF_WRITE);
trace_xfs_buf_error_relse(bp, _RET_IP_);
return false;
}
@ -1109,7 +1125,7 @@ xfs_buf_ioend(
if (!bp->b_error && bp->b_ops)
bp->b_ops->verify_read(bp);
if (!bp->b_error)
bp->b_flags |= XBF_DONE;
xfs_buf_set_flags(bp, XBF_DONE);
if (bp->b_flags & XBF_READ_AHEAD)
percpu_counter_dec(&bp->b_target->bt_readahead_count);
} else {
@ -1119,8 +1135,8 @@ xfs_buf_ioend(
return;
}
} else {
bp->b_flags &= ~XBF_WRITE_FAIL;
bp->b_flags |= XBF_DONE;
xfs_buf_clear_flags(bp, XBF_WRITE_FAIL);
xfs_buf_set_flags(bp, XBF_DONE);
}
/* clear the retry state */
@ -1140,7 +1156,7 @@ xfs_buf_ioend(
bp->b_iodone(bp);
}
bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
xfs_buf_clear_flags(bp, XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
if (async)
xfs_buf_relse(bp);
}
@ -1186,8 +1202,8 @@ xfs_buf_fail(
{
ASSERT(xfs_buf_islocked(bp));
bp->b_flags |= XBF_ASYNC;
bp->b_flags &= ~XBF_DONE;
xfs_buf_set_flags(bp, XBF_ASYNC);
xfs_buf_clear_flags(bp, XBF_DONE);
xfs_buf_stale(bp);
xfs_buf_ioerror(bp, -EIO);
xfs_buf_ioend(bp);
@ -1201,9 +1217,9 @@ xfs_bwrite(
ASSERT(xfs_buf_islocked(bp));
bp->b_flags |= XBF_WRITE;
bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
XBF_DONE);
xfs_buf_set_flags(bp, XBF_WRITE);
xfs_buf_clear_flags(bp, XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
XBF_DONE);
xfs_buf_submit(bp);
error = xfs_buf_iowait(bp);
@ -1394,7 +1410,7 @@ xfs_buf_submit(
return;
ioerror:
bp->b_flags &= ~XBF_DONE;
xfs_buf_clear_flags(bp, XBF_DONE);
xfs_buf_stale(bp);
end_io:
if (bp->b_flags & XBF_ASYNC)
@ -1805,7 +1821,7 @@ xfs_buf_delwri_cancel(
bp = list_first_entry(list, struct xfs_buf, b_list);
xfs_buf_lock(bp);
bp->b_flags &= ~_XBF_DELWRI_Q;
xfs_buf_clear_flags(bp, _XBF_DELWRI_Q);
xfs_buf_list_del(bp);
xfs_buf_relse(bp);
}
@ -1850,7 +1866,7 @@ xfs_buf_delwri_queue(
* might get readded to a delwri list after the synchronous writeout, in
* which case we need just need to re-add the flag here.
*/
bp->b_flags |= _XBF_DELWRI_Q;
xfs_buf_set_flags(bp, _XBF_DELWRI_Q);
if (list_empty(&bp->b_list)) {
xfs_buf_hold(bp);
list_add_tail(&bp->b_list, list);
@ -1927,8 +1943,8 @@ xfs_buf_delwri_submit_prep(
}
trace_xfs_buf_delwri_split(bp, _RET_IP_);
bp->b_flags &= ~_XBF_DELWRI_Q;
bp->b_flags |= XBF_WRITE;
xfs_buf_clear_flags(bp, _XBF_DELWRI_Q);
xfs_buf_set_flags(bp, XBF_WRITE);
return true;
}
@ -1969,7 +1985,7 @@ xfs_buf_delwri_submit_nowait(
}
if (!xfs_buf_delwri_submit_prep(bp))
continue;
bp->b_flags |= XBF_ASYNC;
xfs_buf_set_flags(bp, XBF_ASYNC);
xfs_buf_list_del(bp);
xfs_buf_submit(bp);
}
@ -2002,7 +2018,7 @@ xfs_buf_delwri_submit(
xfs_buf_lock(bp);
if (!xfs_buf_delwri_submit_prep(bp))
continue;
bp->b_flags &= ~XBF_ASYNC;
xfs_buf_clear_flags(bp, XBF_ASYNC);
list_move_tail(&bp->b_list, &wait_list);
xfs_buf_submit(bp);
}