block: support a full bio worth of IO for simplified bdev direct-io

Just alloc the bio_vec array if we exceed the inline limit.

Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7c3ec60..dad97e1 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -193,7 +193,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
        struct file *file = iocb->ki_filp;
        struct block_device *bdev = I_BDEV(bdev_file_inode(file));
        unsigned blkbits = blksize_bits(bdev_logical_block_size(bdev));
-       struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *bvec;
+       struct bio_vec inline_vecs[DIO_INLINE_BIO_VECS], *vecs, *bvec;
        loff_t pos = iocb->ki_pos;
        bool should_dirty = false;
        struct bio bio;
@@ -204,9 +204,17 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
        if ((pos | iov_iter_alignment(iter)) & ((1 << blkbits) - 1))
                return -EINVAL;
 
+       if (nr_pages <= DIO_INLINE_BIO_VECS)
+               vecs = inline_vecs;
+       else {
+               vecs = kmalloc(nr_pages * sizeof(struct bio_vec), GFP_KERNEL);
+               if (!vecs)
+                       return -ENOMEM;
+       }
+
        bio_init(&bio);
        bio.bi_max_vecs = nr_pages;
-       bio.bi_io_vec = inline_vecs;
+       bio.bi_io_vec = vecs;
        bio.bi_bdev = bdev;
        bio.bi_iter.bi_sector = pos >> blkbits;
        bio.bi_private = current;
@@ -243,6 +251,9 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
                put_page(bvec->bv_page);
        }
 
+       if (vecs != inline_vecs)
+               kfree(vecs);
+
        if (unlikely(bio.bi_error))
                return bio.bi_error;
        iocb->ki_pos += ret;
@@ -256,10 +267,10 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
        struct inode *inode = bdev_file_inode(file);
        int nr_pages;
 
-       nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES);
+       nr_pages = iov_iter_npages(iter, BIO_MAX_PAGES + 1);
        if (!nr_pages)
                return 0;
-       if (is_sync_kiocb(iocb) && nr_pages <= DIO_INLINE_BIO_VECS)
+       if (is_sync_kiocb(iocb) && nr_pages <= BIO_MAX_PAGES)
                return __blkdev_direct_IO_simple(iocb, iter, nr_pages);
        return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter,
                                    blkdev_get_block, NULL, NULL,