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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>
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1 changed files with 6 additions and 8 deletions
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@ -96,12 +96,11 @@ static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
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struct address_space *mapping = super->s_mapping_inode->i_mapping;
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struct bio *bio;
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struct page *page;
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struct request_queue *q = bdev_get_queue(sb->s_bdev);
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unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
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unsigned int max_pages;
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int i;
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if (max_pages > BIO_MAX_PAGES)
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max_pages = BIO_MAX_PAGES;
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max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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@ -191,12 +190,11 @@ static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
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{
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struct logfs_super *super = logfs_super(sb);
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struct bio *bio;
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struct request_queue *q = bdev_get_queue(sb->s_bdev);
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unsigned int max_pages = queue_max_hw_sectors(q) >> (PAGE_SHIFT - 9);
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unsigned int max_pages;
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int i;
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if (max_pages > BIO_MAX_PAGES)
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max_pages = BIO_MAX_PAGES;
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max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
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bio = bio_alloc(GFP_NOFS, max_pages);
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BUG_ON(!bio);
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