Messages in this thread Patch in this message | | | Date | Mon, 25 Apr 2005 13:56:19 +1000 | From | Nick Piggin <> | Subject | [patch] __block_write_full_page bug |
| |
Another buffer bug :(
-- SUSE Labs, Novell Inc. When running fsstress -v -d $DIR/tmp -n 1000 -p 1000 -l 2 on an ext2 filesystem with 1024 byte block size, on SMP i386 with 4096 byte page size over loopback to an image file on a tmpfs filesystem, I would very quickly hit BUG_ON(!buffer_async_write(bh)); in fs/buffer.c:end_buffer_async_write
It seems that more than one request would be submitted for a given bh at a time. __block_write_full_page looks like the culprit - with the following patch things are very stable.
Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Index: linux-2.6/fs/buffer.c =================================================================== --- linux-2.6.orig/fs/buffer.c 2005-04-25 13:13:37.000000000 +1000 +++ linux-2.6/fs/buffer.c 2005-04-25 13:14:52.000000000 +1000 @@ -1750,8 +1750,9 @@ static int __block_write_full_page(struc int err; sector_t block; sector_t last_block; - struct buffer_head *bh, *head; - int nr_underway = 0; + struct buffer_head *bh, *head, *arr[MAX_BUF_PER_PAGE]; + int idx = 0; + int nr_underway; BUG_ON(!PageLocked(page)); @@ -1826,6 +1827,7 @@ static int __block_write_full_page(struc } if (test_clear_buffer_dirty(bh)) { mark_buffer_async_write(bh); + arr[idx++] = bh; } else { unlock_buffer(bh); } @@ -1839,15 +1841,12 @@ static int __block_write_full_page(struc set_page_writeback(page); unlock_page(page); - do { - struct buffer_head *next = bh->b_this_page; - if (buffer_async_write(bh)) { + for (nr_underway = 0; nr_underway < idx; nr_underway++) { + bh = arr[nr_underway]; + if (buffer_async_write(bh)) submit_bh(WRITE, bh); - nr_underway++; - } put_bh(bh); - bh = next; - } while (bh != head); + } err = 0; done: @@ -1890,6 +1889,7 @@ recover: if (buffer_mapped(bh) && buffer_dirty(bh)) { lock_buffer(bh); mark_buffer_async_write(bh); + arr[idx++] = bh; } else { /* * The buffer may have been set dirty during @@ -1902,16 +1902,14 @@ recover: BUG_ON(PageWriteback(page)); set_page_writeback(page); unlock_page(page); - do { - struct buffer_head *next = bh->b_this_page; + for (nr_underway = 0; nr_underway < idx; nr_underway++) { + bh = arr[nr_underway]; if (buffer_async_write(bh)) { clear_buffer_dirty(bh); submit_bh(WRITE, bh); - nr_underway++; } put_bh(bh); - bh = next; - } while (bh != head); + } goto done; } @@ -2741,6 +2739,7 @@ sector_t generic_block_bmap(struct addre static int end_bio_bh_io_sync(struct bio *bio, unsigned int bytes_done, int err) { struct buffer_head *bh = bio->bi_private; + bh_end_io_t *end_fn; if (bio->bi_size) return 1; @@ -2750,7 +2749,16 @@ static int end_bio_bh_io_sync(struct bio set_bit(BH_Eopnotsupp, &bh->b_state); } - bh->b_end_io(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); + end_fn = bh->b_end_io; + + /* + * These two lines are debugging only - make sure b_end_io + * isn't run twice for the same io request. + */ + BUG_ON(!end_fn); + bh->b_end_io = NULL; + + end_fn(bh, test_bit(BIO_UPTODATE, &bio->bi_flags)); bio_put(bio); return 0; } | |