linux-kernel - [PATCH v2 2/3] Revert "mm/filemap: avoid buffered read/write race to read inconsistent data"

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Message-ID: <20240124142857.4146716-3-libaokun1@huawei.com>
Date: Wed, 24 Jan 2024 22:28:56 +0800
From: Baokun Li <libaokun1@...wei.com>
To: <linux-fsdevel@...r.kernel.org>
CC: <torvalds@...ux-foundation.org>, <viro@...iv.linux.org.uk>,
	<brauner@...nel.org>, <jack@...e.cz>, <willy@...radead.org>,
	<akpm@...ux-foundation.org>, <arnd@...db.de>, <linux-arch@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <yi.zhang@...wei.com>,
	<yangerkun@...wei.com>, <yukuai3@...wei.com>, <libaokun1@...wei.com>
Subject: [PATCH v2 2/3] Revert "mm/filemap: avoid buffered read/write race to read inconsistent data"

This reverts commit e2c27b803bb6 ("mm/filemap: avoid buffered read/write
race to read inconsistent data"). After making the i_size_read/write
helpers be smp_load_acquire/store_release(), it is already guaranteed that
changes to page contents are visible before we see increased inode size,
so the extra smp_rmb() in filemap_read() can be removed.

Signed-off-by: Baokun Li <libaokun1@...wei.com>
---
 mm/filemap.c | 9 ---------
 1 file changed, 9 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 142864338ca4..bed844b07e87 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2608,15 +2608,6 @@ ssize_t filemap_read(struct kiocb *iocb, struct iov_iter *iter,
 			goto put_folios;
 		end_offset = min_t(loff_t, isize, iocb->ki_pos + iter->count);
 
-		/*
-		 * Pairs with a barrier in
-		 * block_write_end()->mark_buffer_dirty() or other page
-		 * dirtying routines like iomap_write_end() to ensure
-		 * changes to page contents are visible before we see
-		 * increased inode size.
-		 */
-		smp_rmb();
-
 		/*
 		 * Once we start copying data, we don't want to be touching any
 		 * cachelines that might be contended:
-- 
2.31.1