From: Chen, Kenneth W Date: Tue, 23 Jan 2007 04:40:43 +0000 (-0800) Subject: [PATCH] fix blk_direct_IO bio preparation X-Git-Tag: v2.6.20-rc6~35 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cda9205da24aeaa8fb086b0fb85cdf39571ecc3f;p=linux-2.6 [PATCH] fix blk_direct_IO bio preparation For large size DIO that needs multiple bio, one full page worth of data was lost at the boundary of bio's maximum sector or segment limits. After a bio is full and got submitted. The outer while (nbytes) { ... } loop will allocate a new bio and just march on to index into next page. It just forgets about the page that bio_add_page() rejected when previous bio is full. Fix it by put the rejected page back to pvec so we pick it up again for the next bio. Signed-off-by: Ken Chen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/fs/block_dev.c b/fs/block_dev.c index da020be25d..d9bdf2b3ad 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -190,6 +190,12 @@ static struct page *blk_get_page(unsigned long addr, size_t count, int rw, return pvec->page[pvec->idx++]; } +/* return a page back to pvec array */ +static void blk_unget_page(struct page *page, struct pvec *pvec) +{ + pvec->page[--pvec->idx] = page; +} + static ssize_t blkdev_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov, loff_t pos, unsigned long nr_segs) @@ -278,6 +284,8 @@ same_bio: count = min(count, nbytes); goto same_bio; } + } else { + blk_unget_page(page, &pvec); } /* bio is ready, submit it */