ext4: Fix data corruption with multi-block writepages support (d50bdd5a) · Commits · 戴 / test

This fixes a corruption problem with the multi-block writepages submittal change for ext4, from commit ("ext4: use bio layer instead of buffer layer in mpage_da_submit_io"). (Note that this corruption is not present in 2.6.37 on ext4, because the corruption was detected after the feature was merged in 2.6.37-rc1, and so it was turned off by adding a non-default mount option, mblk_io_submit. With this commit, which hopefully fixes the last of the bugs with this feature, we'll be able to turn on this performance feature by default in 2.6.38, and remove the mblk_io_submit option.) The ext4 code path to bundle multiple pages for writeback in ext4_bio_write_page() had a bug: we should be clearing buffer head dirty flags *before* we submit the bio, not in the completion routine. The patch below was tested on 2.6.37 under KVM with the postgresql script which was submitted by Jon Nelson as documented in commit . Without the patch, I'd hit the corruption problem about 50-70% of the time. With the patch, I executed the script > 100 times with no corruption seen. I also fixed a bug to make sure ext4_end_bio() doesn't dereference the bio after the bio_put() call. Reported-by:

Jon Nelson <jnelson@jamponi.net> Reported-by:

Matthias Bayer <jackdachef@gmail.com> Signed-off-by:

Curt Wohlgemuth <curtw@google.com> Signed-off-by:

"Theodore Ts'o" <tytso@mit.edu> Cc: stable@kernel.org

fs/ext4/page-io.c

+6 −5

Original line number	Diff line number	Diff line
		@@ -190,6 +190,7 @@ static void ext4_end_bio(struct bio *bio, int error)
		struct inode *inode;
		unsigned long flags;
		int i;
		sector_t bi_sector = bio->bi_sector;

		BUG_ON(!io_end);
		bio->bi_private = NULL;
		@@ -207,9 +208,7 @@ static void ext4_end_bio(struct bio *bio, int error)
		if (error)
		SetPageError(page);
		BUG_ON(!head);
		if (head->b_size == PAGE_CACHE_SIZE)
		clear_buffer_dirty(head);
		else {
		if (head->b_size != PAGE_CACHE_SIZE) {
		loff_t offset;
		loff_t io_end_offset = io_end->offset + io_end->size;

		@@ -221,7 +220,6 @@ static void ext4_end_bio(struct bio *bio, int error)
		if (error)
		buffer_io_error(bh);

		clear_buffer_dirty(bh);
		}
		if (buffer_delay(bh))
		partial_write = 1;
		@@ -257,7 +255,7 @@ static void ext4_end_bio(struct bio *bio, int error)
		(unsigned long long) io_end->offset,
		(long) io_end->size,
		(unsigned long long)
		bio->bi_sector >> (inode->i_blkbits - 9));
		bi_sector >> (inode->i_blkbits - 9));
		}

		/* Add the io_end to per-inode completed io list*/
		@@ -380,6 +378,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,

		blocksize = 1 << inode->i_blkbits;

		BUG_ON(!PageLocked(page));
		BUG_ON(PageWriteback(page));
		set_page_writeback(page);
		ClearPageError(page);
		@@ -397,12 +396,14 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
		for (bh = head = page_buffers(page), block_start = 0;
		bh != head \|\| !block_start;
		block_start = block_end, bh = bh->b_this_page) {

		block_end = block_start + blocksize;
		if (block_start >= len) {
		clear_buffer_dirty(bh);
		set_buffer_uptodate(bh);
		continue;
		}
		clear_buffer_dirty(bh);
		ret = io_submit_add_bh(io, io_page, inode, wbc, bh);
		if (ret) {
		/*

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