From 9f0bbd8ca7905fcc0602c038013b095322fec939 Mon Sep 17 00:00:00 2001 From: Prasad Joshi Date: Mon, 23 Jul 2012 10:32:11 +0530 Subject: [PATCH] logfs: query block device for number of pages to send with bio The block device driver puts a limit on maximum number of pages that can be sent with the bio. Not all block devices can handle BIO_MAX_PAGES number of pages in bio. Specifically the virtio-blk diriver limits it to 126. When the LogFS file system was excersized in KVM, the following bug from do_virtblk_request() was observed static void do_virtblk_request(struct request_queue *q) { .... .... while ((req = blk_peek_request(q)) != NULL) { BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems); .... .... } .... } The patch fixes the problem by querring the maximum number of pages in bio allowed from block device driver and then using those many pages during submit_bio. Signed-off-by: Prasad Joshi --- fs/logfs/dev_bdev.c | 14 ++++++-------- 1 file changed, 6 insertions(+), 8 deletions(-) diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c index ea29df36893..e784a217b50 100644 --- a/fs/logfs/dev_bdev.c +++ b/fs/logfs/dev_bdev.c @@ -96,12 +96,11 @@ static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index, struct address_space *mapping = super->s_mapping_inode->i_mapping; struct bio *bio; struct page *page; - struct request_queue *q = bdev_get_queue(sb->s_bdev); - unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9); + unsigned int max_pages; int i; - if (max_pages > BIO_MAX_PAGES) - max_pages = BIO_MAX_PAGES; + max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev)); + bio = bio_alloc(GFP_NOFS, max_pages); BUG_ON(!bio); @@ -191,12 +190,11 @@ static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index, { struct logfs_super *super = logfs_super(sb); struct bio *bio; - struct request_queue *q = bdev_get_queue(sb->s_bdev); - unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9); + unsigned int max_pages; int i; - if (max_pages > BIO_MAX_PAGES) - max_pages = BIO_MAX_PAGES; + max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev)); + bio = bio_alloc(GFP_NOFS, max_pages); BUG_ON(!bio);