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authorPrasad Joshi <prasadjoshi.linux@gmail.com>2012-07-23 10:32:11 +0530
committerPrasad Joshi <prasadjoshi.linux@gmail.com>2012-07-23 10:32:11 +0530
commit9f0bbd8ca7905fcc0602c038013b095322fec939 (patch)
treed35de1ee5a475adc9d9e55432ff0ddb271343096
parent41b93bc1ee7e7276db698dd66afa7b740cda517a (diff)
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 <prasadjoshi.linux@gmail.com>
-rw-r--r--fs/logfs/dev_bdev.c14
1 files changed, 6 insertions, 8 deletions
diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index ea29df36893d..e784a217b500 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);