From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0A00C396B9A for ; Wed, 15 Jul 2026 14:52:12 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.133 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784127134; cv=none; b=pFqHo6GlrYM6jnaeabhDmqPr4WKRljlM895fwQ9jWEEr/44Z4oMytFMMWRRng07atW5KtZe8K1LFKCztOIRuaMElk57xpNI7pKujV7Py2jGRT3NW+OUSAdVSLkJBqapNRx60fvMTZeqTJbIXOevGKHwrjjfkSMYNnPEaTeduDgM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784127134; c=relaxed/simple; bh=5QdOGFRX/urfY8lubDuCQkC43WjG1+t1jCmBa57CP+o=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=JNIEfwDSvgzIygH+McY5ikQpe5ZNdUFkpu08G60RytWESbp6HEEByw9QI+6LVtt6+A5C/LgsLrjhgu+zErYRqyGVCTllk2WLv46NWmV2wSOy9m5UAZwb0XX000gzb3BDYbsbtPy1e+mFZIS3aFsoDWWJr39mY5fQDeCuqZu4VKc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=lst.de; spf=none smtp.mailfrom=bombadil.srs.infradead.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b=D2gWsRZk; arc=none smtp.client-ip=198.137.202.133 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=lst.de Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=bombadil.srs.infradead.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="D2gWsRZk" DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-ID:Date:Subject:Cc:To:From:Sender :Reply-To:Content-Type:Content-ID:Content-Description; bh=cT4FwpLRqCqQcRDfD/kOOYzyZ0lMl8IixRn6ZLCTxkw=; b=D2gWsRZkw1GHLrnrlUkaU8evIu AP2uJLrycz2JPv582kALuKCN4Q3sOC9en87ybZ8dMniMehakKbJjSNuEPcAz8bCqaZu/kw6gF3Fxj I5fHIo96lCe5hX7fdzff591hqHhqRzHvllhX3RQ2i1xVccyoOMhHHkWChBs3QqPbYeoVQNGlw1J54 hDhJd3mNRfMcOz+xxUgFw1rfnGh57JZAfolftHpdpMaAd2ACuJVVTmoyCDbGuBpHSFV0Wfq45LKQA YSRIZJ5aLZBpxhhLM8b6k6l1srFWRbGn1t26ovzyMmbTGNonXdBKZ+ZXuJuDii47gETRjVb6dXgxH HGVof31w==; Received: from 2a02-8389-2301-9f00-b29a-36e9-8c1c-0994.cable.dynamic.v6.surfer.at ([2a02:8389:2301:9f00:b29a:36e9:8c1c:994] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.99.1 #2 (Red Hat Linux)) id 1wk0y4-0000000FDX8-0O6I; Wed, 15 Jul 2026 14:52:12 +0000 From: Christoph Hellwig To: Carlos Maiolino Cc: "Darrick J. Wong" , linux-xfs@vger.kernel.org Subject: [PATCH 07/12] xfs: use WRITE_ONCE to update b_flags Date: Wed, 15 Jul 2026 16:51:00 +0200 Message-ID: <20260715145147.95654-8-hch@lst.de> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260715145147.95654-1-hch@lst.de> References: <20260715145147.95654-1-hch@lst.de> Precedence: bulk X-Mailing-List: linux-xfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html 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 --- fs/xfs/xfs_buf.c | 86 ++++++++++++++++++++++++++++-------------------- 1 file changed, 51 insertions(+), 35 deletions(-) diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 33e904d838f4..2a0a19172847 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -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); } -- 2.53.0