block: remove bio_get_nr_vecs()

We can always fill up the bio now, no need to estimate the possible
size based on queue parameters.

Acked-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
[hch: rebased and wrote a changelog]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ming Lin <ming.l@ssi.samsung.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

16 files changed, 18 insertions, 74 deletions

diff --git a/block/bio.c b/block/bio.c
index ba9c4b0c0ff2..425d6d4a2f7a 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -694,29 +694,6 @@ integrity_clone:
 EXPORT_SYMBOL(bio_clone_bioset);
 
 /**
- *      bio_get_nr_vecs         - return approx number of vecs
- *      @bdev:  I/O target
- *
- *      Return the approximate number of pages we can send to this target.
- *      There's no guarantee that you will be able to fit this number of pages
- *      into a bio, it does not account for dynamic restrictions that vary
- *      on offset.
- */
-int bio_get_nr_vecs(struct block_device *bdev)
-{
-        struct request_queue *q = bdev_get_queue(bdev);
-        int nr_pages;
-
-        nr_pages = min_t(unsigned,
-                     queue_max_segments(q),
-                     queue_max_sectors(q) / (PAGE_SIZE >> 9) + 1);
-
-        return min_t(unsigned, nr_pages, BIO_MAX_PAGES);
-
-}
-EXPORT_SYMBOL(bio_get_nr_vecs);
-
-/**
  *      bio_add_pc_page -       attempt to add page to bio
  *      @q: the target queue
  *      @bio: destination bio
diff --git a/drivers/md/dm-io.c b/drivers/md/dm-io.c
index c84714f70378..6f8e83b2a6f8 100644
--- a/drivers/md/dm-io.c
+++ b/drivers/md/dm-io.c
@@ -316,7 +316,7 @@ static void do_region(int rw, unsigned region, struct dm_io_region *where,
                 if ((rw & REQ_DISCARD) || (rw & REQ_WRITE_SAME))
                         num_bvecs = 1;
                 else
-                        num_bvecs = min_t(int, bio_get_nr_vecs(where->bdev),
+                        num_bvecs = min_t(int, BIO_MAX_PAGES,
                                           dm_sector_div_up(remaining, (PAGE_SIZE >> SECTOR_SHIFT)));
 
                 bio = bio_alloc_bioset(GFP_NOIO, num_bvecs, io->client->bios);
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 302266ec2cdb..57ee8ca29b06 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -97,10 +97,7 @@ static inline int compressed_bio_size(struct btrfs_root *root,
 static struct bio *compressed_bio_alloc(struct block_device *bdev,
                                         u64 first_byte, gfp_t gfp_flags)
 {
-        int nr_vecs;
-
-        nr_vecs = bio_get_nr_vecs(bdev);
-        return btrfs_bio_alloc(bdev, first_byte >> 9, nr_vecs, gfp_flags);
+        return btrfs_bio_alloc(bdev, first_byte >> 9, BIO_MAX_PAGES, gfp_flags);
 }
 
 static int check_compressed_csum(struct inode *inode,
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index c22f175ed024..68b12bbc709f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2795,9 +2795,7 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree,
 {
         int ret = 0;
         struct bio *bio;
-        int nr;
         int contig = 0;
-        int this_compressed = bio_flags & EXTENT_BIO_COMPRESSED;
         int old_compressed = prev_bio_flags & EXTENT_BIO_COMPRESSED;
         size_t page_size = min_t(size_t, size, PAGE_CACHE_SIZE);
 
@@ -2822,12 +2820,9 @@ static int submit_extent_page(int rw, struct extent_io_tree *tree,
                         return 0;
                 }
         }
-        if (this_compressed)
-                nr = BIO_MAX_PAGES;
-        else
-                nr = bio_get_nr_vecs(bdev);
 
-        bio = btrfs_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
+        bio = btrfs_bio_alloc(bdev, sector, BIO_MAX_PAGES,
+                        GFP_NOFS | __GFP_HIGH);
         if (!bio)
                 return -ENOMEM;
 
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6b8becfe2057..8635ef01a04a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7959,8 +7959,7 @@ out:
 static struct bio *btrfs_dio_bio_alloc(struct block_device *bdev,
                                        u64 first_sector, gfp_t gfp_flags)
 {
-        int nr_vecs = bio_get_nr_vecs(bdev);
-        return btrfs_bio_alloc(bdev, first_sector, nr_vecs, gfp_flags);
+        return btrfs_bio_alloc(bdev, first_sector, BIO_MAX_PAGES, gfp_flags);
 }
 
 static inline int btrfs_lookup_and_bind_dio_csum(struct btrfs_root *root,
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index ebb8260186fe..9c146d8307b5 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -454,27 +454,14 @@ struct scrub_ctx *scrub_setup_ctx(struct btrfs_device *dev, int is_dev_replace)
         struct scrub_ctx *sctx;
         int             i;
         struct btrfs_fs_info *fs_info = dev->dev_root->fs_info;
-        int pages_per_rd_bio;
         int ret;
 
-        /*
-         * the setting of pages_per_rd_bio is correct for scrub but might
-         * be wrong for the dev_replace code where we might read from
-         * different devices in the initial huge bios. However, that
-         * code is able to correctly handle the case when adding a page
-         * to a bio fails.
-         */
-        if (dev->bdev)
-                pages_per_rd_bio = min_t(int, SCRUB_PAGES_PER_RD_BIO,
-                                         bio_get_nr_vecs(dev->bdev));
-        else
-                pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
         sctx = kzalloc(sizeof(*sctx), GFP_NOFS);
         if (!sctx)
                 goto nomem;
         atomic_set(&sctx->refs, 1);
         sctx->is_dev_replace = is_dev_replace;
-        sctx->pages_per_rd_bio = pages_per_rd_bio;
+        sctx->pages_per_rd_bio = SCRUB_PAGES_PER_RD_BIO;
         sctx->curr = -1;
         sctx->dev_root = dev->dev_root;
         for (i = 0; i < SCRUB_BIOS_PER_SCTX; ++i) {
@@ -3896,8 +3883,7 @@ static int scrub_setup_wr_ctx(struct scrub_ctx *sctx,
                 return 0;
 
         WARN_ON(!dev->bdev);
-        wr_ctx->pages_per_wr_bio = min_t(int, SCRUB_PAGES_PER_WR_BIO,
-                                         bio_get_nr_vecs(dev->bdev));
+        wr_ctx->pages_per_wr_bio = SCRUB_PAGES_PER_WR_BIO;
         wr_ctx->tgtdev = dev;
         atomic_set(&wr_ctx->flush_all_writes, 0);
         return 0;
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 818c647f36d3..11256291642e 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -655,7 +655,7 @@ static inline int dio_new_bio(struct dio *dio, struct dio_submit *sdio,
         if (ret)
                 goto out;
         sector = start_sector << (sdio->blkbits - 9);
-        nr_pages = min(sdio->pages_in_io, bio_get_nr_vecs(map_bh->b_bdev));
+        nr_pages = min(sdio->pages_in_io, BIO_MAX_PAGES);
         BUG_ON(nr_pages <= 0);
         dio_bio_alloc(dio, sdio, map_bh->b_bdev, sector, nr_pages);
         sdio->boundary = 0;
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index aa95566f14be..8a9d63a0c071 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -372,10 +372,9 @@ void ext4_io_submit_init(struct ext4_io_submit *io,
 static int io_submit_init_bio(struct ext4_io_submit *io,
                               struct buffer_head *bh)
 {
-        int nvecs = bio_get_nr_vecs(bh->b_bdev);
         struct bio *bio;
 
-        bio = bio_alloc(GFP_NOIO, min(nvecs, BIO_MAX_PAGES));
+        bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
         if (!bio)
                 return -ENOMEM;
         bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index 5de5b871c178..e26803fb210d 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -284,7 +284,7 @@ int ext4_mpage_readpages(struct address_space *mapping,
                                         goto set_error_page;
                         }
                         bio = bio_alloc(GFP_KERNEL,
-                                min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
+                                min_t(int, nr_pages, BIO_MAX_PAGES));
                         if (!bio) {
                                 if (ctx)
                                         ext4_release_crypto_ctx(ctx);
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 8f0baa7ffb50..b478accb24d9 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1552,7 +1552,7 @@ submit_and_realloc:
                         }
 
                         bio = bio_alloc(GFP_KERNEL,
-                                min_t(int, nr_pages, bio_get_nr_vecs(bdev)));
+                                min_t(int, nr_pages, BIO_MAX_PAGES));
                         if (!bio) {
                                 if (ctx)
                                         f2fs_release_crypto_ctx(ctx);
diff --git a/fs/gfs2/lops.c b/fs/gfs2/lops.c
index c0a1b967deba..92324ac58290 100644
--- a/fs/gfs2/lops.c
+++ b/fs/gfs2/lops.c
@@ -261,18 +261,11 @@ void gfs2_log_flush_bio(struct gfs2_sbd *sdp, int rw)
 static struct bio *gfs2_log_alloc_bio(struct gfs2_sbd *sdp, u64 blkno)
 {
         struct super_block *sb = sdp->sd_vfs;
-        unsigned nrvecs = bio_get_nr_vecs(sb->s_bdev);
         struct bio *bio;
 
         BUG_ON(sdp->sd_log_bio);
 
-        while (1) {
-                bio = bio_alloc(GFP_NOIO, nrvecs);
-                if (likely(bio))
-                        break;
-                nrvecs = max(nrvecs/2, 1U);
-        }
-
+        bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
         bio->bi_iter.bi_sector = blkno * (sb->s_blocksize >> 9);
         bio->bi_bdev = sb->s_bdev;
         bio->bi_end_io = gfs2_end_log_write;
diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index cea0cc9878b7..a7fdbd868474 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -81,7 +81,7 @@ static int __bdev_writeseg(struct super_block *sb, u64 ofs, pgoff_t index,
         unsigned int max_pages;
         int i;
 
-        max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
+        max_pages = min(nr_pages, BIO_MAX_PAGES);
 
         bio = bio_alloc(GFP_NOFS, max_pages);
         BUG_ON(!bio);
@@ -171,7 +171,7 @@ static int do_erase(struct super_block *sb, u64 ofs, pgoff_t index,
         unsigned int max_pages;
         int i;
 
-        max_pages = min(nr_pages, (size_t) bio_get_nr_vecs(super->s_bdev));
+        max_pages = min(nr_pages, BIO_MAX_PAGES);
 
         bio = bio_alloc(GFP_NOFS, max_pages);
         BUG_ON(!bio);
diff --git a/fs/mpage.c b/fs/mpage.c
index abac9361b3f1..778a4ddef77a 100644
--- a/fs/mpage.c
+++ b/fs/mpage.c
@@ -277,7 +277,7 @@ alloc_new:
                                 goto out;
                 }
                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
-                                min_t(int, nr_pages, bio_get_nr_vecs(bdev)),
+                                min_t(int, nr_pages, BIO_MAX_PAGES),
                                 GFP_KERNEL);
                 if (bio == NULL)
                         goto confused;
@@ -602,7 +602,7 @@ alloc_new:
                         }
                 }
                 bio = mpage_alloc(bdev, blocks[0] << (blkbits - 9),
-                                bio_get_nr_vecs(bdev), GFP_NOFS|__GFP_HIGH);
+                                BIO_MAX_PAGES, GFP_NOFS|__GFP_HIGH);
                 if (bio == NULL)
                         goto confused;
 
diff --git a/fs/nilfs2/segbuf.c b/fs/nilfs2/segbuf.c
index 550b10efb14e..f63620ce3892 100644
--- a/fs/nilfs2/segbuf.c
+++ b/fs/nilfs2/segbuf.c
@@ -414,7 +414,7 @@ static void nilfs_segbuf_prepare_write(struct nilfs_segment_buffer *segbuf,
 {
         wi->bio = NULL;
         wi->rest_blocks = segbuf->sb_sum.nblocks;
-        wi->max_pages = bio_get_nr_vecs(wi->nilfs->ns_bdev);
+        wi->max_pages = BIO_MAX_PAGES;
         wi->nr_vecs = min(wi->max_pages, wi->rest_blocks);
         wi->start = wi->end = 0;
         wi->blocknr = segbuf->sb_pseg_start;
diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 3714844a81d8..c77499bcbd7a 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -381,8 +381,7 @@ STATIC struct bio *
 xfs_alloc_ioend_bio(
         struct buffer_head      *bh)
 {
-        int                     nvecs = bio_get_nr_vecs(bh->b_bdev);
-        struct bio              *bio = bio_alloc(GFP_NOIO, nvecs);
+        struct bio              *bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
 
         ASSERT(bio->bi_private == NULL);
         bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
diff --git a/include/linux/bio.h b/include/linux/bio.h
index b7892a1906bd..ad7217458812 100644
--- a/include/linux/bio.h
+++ b/include/linux/bio.h
@@ -460,7 +460,6 @@ void bio_chain(struct bio *, struct bio *);
 extern int bio_add_page(struct bio *, struct page *, unsigned int,unsigned int);
 extern int bio_add_pc_page(struct request_queue *, struct bio *, struct page *,
                            unsigned int, unsigned int);
-extern int bio_get_nr_vecs(struct block_device *);
 struct rq_map_data;
 extern struct bio *bio_map_user_iov(struct request_queue *,
                                     const struct iov_iter *, gfp_t);