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authorTheodore Ts'o <tytso@mit.edu>2015-06-12 23:45:33 -0400
committerZefan Li <lizefan@huawei.com>2015-10-22 09:20:04 +0800
commit0c0fd01eee9d08fdedd5a9de4656c32a422844a7 (patch)
treeb6f7a64d2bfff1b0510317bf22dbb5e8416b7194
parentae6b0bc8ea85a9dcc11fc2525e821a22ebbb7c83 (diff)
ext4: fix race between truncate and __ext4_journalled_writepage()
commit bdf96838aea6a265f2ae6cbcfb12a778c84a0b8e upstream. The commit cf108bca465d: "ext4: Invert the locking order of page_lock and transaction start" caused __ext4_journalled_writepage() to drop the page lock before the page was written back, as part of changing the locking order to jbd2_journal_start -> page_lock. However, this introduced a potential race if there was a truncate racing with the data=journalled writeback mode. Fix this by grabbing the page lock after starting the journal handle, and then checking to see if page had gotten truncated out from under us. This fixes a number of different warnings or BUG_ON's when running xfstests generic/086 in data=journalled mode, including: jbd2_journal_dirty_metadata: vdc-8: bad jh for block 115643: transaction (ee3fe7 c0, 164), jh->b_transaction ( (null), 0), jh->b_next_transaction ( (null), 0), jlist 0 - and - kernel BUG at /usr/projects/linux/ext4/fs/jbd2/transaction.c:2200! ... Call Trace: [<c02b2ded>] ? __ext4_journalled_invalidatepage+0x117/0x117 [<c02b2de5>] __ext4_journalled_invalidatepage+0x10f/0x117 [<c02b2ded>] ? __ext4_journalled_invalidatepage+0x117/0x117 [<c027d883>] ? lock_buffer+0x36/0x36 [<c02b2dfa>] ext4_journalled_invalidatepage+0xd/0x22 [<c0229139>] do_invalidatepage+0x22/0x26 [<c0229198>] truncate_inode_page+0x5b/0x85 [<c022934b>] truncate_inode_pages_range+0x156/0x38c [<c0229592>] truncate_inode_pages+0x11/0x15 [<c022962d>] truncate_pagecache+0x55/0x71 [<c02b913b>] ext4_setattr+0x4a9/0x560 [<c01ca542>] ? current_kernel_time+0x10/0x44 [<c026c4d8>] notify_change+0x1c7/0x2be [<c0256a00>] do_truncate+0x65/0x85 [<c0226f31>] ? file_ra_state_init+0x12/0x29 - and - WARNING: CPU: 1 PID: 1331 at /usr/projects/linux/ext4/fs/jbd2/transaction.c:1396 irty_metadata+0x14a/0x1ae() ... Call Trace: [<c01b879f>] ? console_unlock+0x3a1/0x3ce [<c082cbb4>] dump_stack+0x48/0x60 [<c0178b65>] warn_slowpath_common+0x89/0xa0 [<c02ef2cf>] ? jbd2_journal_dirty_metadata+0x14a/0x1ae [<c0178bef>] warn_slowpath_null+0x14/0x18 [<c02ef2cf>] jbd2_journal_dirty_metadata+0x14a/0x1ae [<c02d8615>] __ext4_handle_dirty_metadata+0xd4/0x19d [<c02b2f44>] write_end_fn+0x40/0x53 [<c02b4a16>] ext4_walk_page_buffers+0x4e/0x6a [<c02b59e7>] ext4_writepage+0x354/0x3b8 [<c02b2f04>] ? mpage_release_unused_pages+0xd4/0xd4 [<c02b1b21>] ? wait_on_buffer+0x2c/0x2c [<c02b5a4b>] ? ext4_writepage+0x3b8/0x3b8 [<c02b5a5b>] __writepage+0x10/0x2e [<c0225956>] write_cache_pages+0x22d/0x32c [<c02b5a4b>] ? ext4_writepage+0x3b8/0x3b8 [<c02b6ee8>] ext4_writepages+0x102/0x607 [<c019adfe>] ? sched_clock_local+0x10/0x10e [<c01a8a7c>] ? __lock_is_held+0x2e/0x44 [<c01a8ad5>] ? lock_is_held+0x43/0x51 [<c0226dff>] do_writepages+0x1c/0x29 [<c0276bed>] __writeback_single_inode+0xc3/0x545 [<c0277c07>] writeback_sb_inodes+0x21f/0x36d ... Signed-off-by: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Zefan Li <lizefan@huawei.com>
-rw-r--r--fs/ext4/inode.c22
1 files changed, 19 insertions, 3 deletions
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9e9db425c613..facf1cf46eee 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1848,18 +1848,32 @@ static int __ext4_journalled_writepage(struct page *page,
page_bufs = page_buffers(page);
BUG_ON(!page_bufs);
walk_page_buffers(handle, page_bufs, 0, len, NULL, bget_one);
- /* As soon as we unlock the page, it can go away, but we have
- * references to buffers so we are safe */
+ /*
+ * We need to release the page lock before we start the
+ * journal, so grab a reference so the page won't disappear
+ * out from under us.
+ */
+ get_page(page);
unlock_page(page);
handle = ext4_journal_start(inode, ext4_writepage_trans_blocks(inode));
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
- goto out;
+ put_page(page);
+ goto out_no_pagelock;
}
BUG_ON(!ext4_handle_valid(handle));
+ lock_page(page);
+ put_page(page);
+ if (page->mapping != mapping) {
+ /* The page got truncated from under us */
+ ext4_journal_stop(handle);
+ ret = 0;
+ goto out;
+ }
+
ret = walk_page_buffers(handle, page_bufs, 0, len, NULL,
do_journal_get_write_access);
@@ -1875,6 +1889,8 @@ static int __ext4_journalled_writepage(struct page *page,
walk_page_buffers(handle, page_bufs, 0, len, NULL, bput_one);
ext4_set_inode_state(inode, EXT4_STATE_JDATA);
out:
+ unlock_page(page);
+out_no_pagelock:
return ret;
}