ext4: Resolve the hang of direct i/o read in handling EXT4_IO_END_UNWRITTEN. (32c80b32) · Commits · 戴 / test

EXT4_IO_END_UNWRITTEN flag set and the increase of i_aiodio_unwritten should be done simultaneously since ext4_end_io_nolock always clear the flag and decrease the counter in the same time. We don't increase i_aiodio_unwritten when setting EXT4_IO_END_UNWRITTEN so it will go nagative and causes some process to wait forever. Part of the patch came from Eric in his e-mail, but it doesn't fix the problem met by Michael actually. http://marc.info/?l=linux-ext4&m=131316851417460&w=2 Reported-and-Tested-by:

Michael <Tokarev<mjt@tls.msk.ru> Signed-off-by:

Eric Sandeen <sandeen@redhat.com> Signed-off-by:

Tao Ma <boyu.mt@taobao.com> Signed-off-by:

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

fs/ext4/inode.c

+8 −1

Original line number	Diff line number	Diff line
		@@ -2678,8 +2678,15 @@ static void ext4_end_io_buffer_write(struct buffer_head *bh, int uptodate)
		goto out;
		}

		io_end->flag = EXT4_IO_END_UNWRITTEN;
		/*
		* It may be over-defensive here to check EXT4_IO_END_UNWRITTEN now,
		* but being more careful is always safe for the future change.
		*/
		inode = io_end->inode;
		if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
		io_end->flag \|= EXT4_IO_END_UNWRITTEN;
		atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
		}

		/* Add the io_end to per-inode completed io list*/
		spin_lock_irqsave(&EXT4_I(inode)->i_completed_io_lock, flags);

fs/ext4/page-io.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -334,8 +334,10 @@ submit_and_retry:
		if ((io_end->num_io_pages >= MAX_IO_PAGES) &&
		(io_end->pages[io_end->num_io_pages-1] != io_page))
		goto submit_and_retry;
		if (buffer_uninit(bh))
		io->io_end->flag \|= EXT4_IO_END_UNWRITTEN;
		if (buffer_uninit(bh) && !(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
		io_end->flag \|= EXT4_IO_END_UNWRITTEN;
		atomic_inc(&EXT4_I(inode)->i_aiodio_unwritten);
		}
		io->io_end->size += bh->b_size;
		io->io_next_block++;
		ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh));

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