From b43d17f319f2c502b17139d1cf70731b2b62c644 Mon Sep 17 00:00:00 2001 From: Curt Wohlgemuth Date: Mon, 5 Mar 2012 10:40:15 -0500 Subject: [PATCH] ext4: don't release page refs in ext4_end_bio() We can clear PageWriteback on each page when the IO completes, but we can't release the references on the page until we convert any uninitialized extents. Without this patch, the use of the dioread_nolock mount option can break buffered writes, because extents may not be converted by the time a subsequent buffered read comes in; if the page is not in the page cache, a read will return zeros if the extent is still uninitialized. I tested this with a (temporary) patch that adds a call to msleep(1000) at the start of ext4_end_io_work(), to delay processing of each DIO-unwritten work queue item. With this msleep(), a simple workload of fallocate write fadvise read will fail without this patch, succeeds with it. Signed-off-by: Curt Wohlgemuth Signed-off-by: "Theodore Ts'o" --- fs/ext4/page-io.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index dcdeef169a69..74cd1f7f1f88 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -60,7 +60,6 @@ void ext4_ioend_wait(struct inode *inode) static void put_io_page(struct ext4_io_page *io_page) { if (atomic_dec_and_test(&io_page->p_count)) { - end_page_writeback(io_page->p_page); put_page(io_page->p_page); kmem_cache_free(io_page_cachep, io_page); } @@ -234,9 +233,9 @@ static void ext4_end_bio(struct bio *bio, int error) } while (bh != head); } - put_io_page(io_end->pages[i]); + if (atomic_read(&io_end->pages[i]->p_count) == 1) + end_page_writeback(io_end->pages[i]->p_page); } - io_end->num_io_pages = 0; inode = io_end->inode; if (error) { @@ -428,6 +427,8 @@ int ext4_bio_write_page(struct ext4_io_submit *io, * PageWriteback bit from the page to prevent the system from * wedging later on. */ + if (atomic_read(&io_page->p_count) == 1) + end_page_writeback(page); put_io_page(io_page); return ret; } -- 2.39.5