loop: convert to using splice_direct_to_actor() instead of sendfile()

This gets rid of the dependency on ->sendfile() for receiving data
and converts loop to ->splice_read() instead.

Also includes an IV offset fix from Hugh Dickins.

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

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0ed5470d25339674a5c449feab66f5505db5f3c2..87d84e7d54321e08d1a451905a759241f055ca8e 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -74,6 +74,7 @@
 #include <linux/highmem.h>
 #include <linux/gfp.h>
 #include <linux/kthread.h>
+#include <linux/pipe_fs_i.h>
 
 #include <asm/uaccess.h>
 
@@ -401,50 +402,73 @@ struct lo_read_data {
 };
 
 static int
-lo_read_actor(read_descriptor_t *desc, struct page *page,
-             unsigned long offset, unsigned long size)
+lo_splice_actor(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
+               struct splice_desc *sd)
 {
-       unsigned long count = desc->count;
-       struct lo_read_data *p = desc->arg.data;
+       struct lo_read_data *p = sd->u.data;
        struct loop_device *lo = p->lo;
+       struct page *page = buf->page;
        sector_t IV;
+       size_t size;
+       int ret;
 
-       IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9);
+       ret = buf->ops->pin(pipe, buf);
+       if (unlikely(ret))
+               return ret;
 
-       if (size > count)
-               size = count;
+       IV = ((sector_t) page->index << (PAGE_CACHE_SHIFT - 9)) +
+                                                       (buf->offset >> 9);
+       size = sd->len;
+       if (size > p->bsize)
+               size = p->bsize;
 
-       if (lo_do_transfer(lo, READ, page, offset, p->page, p->offset, size, IV)) {
-               size = 0;
+       if (lo_do_transfer(lo, READ, page, buf->offset, p->page, p->offset, size, IV)) {
                printk(KERN_ERR "loop: transfer error block %ld\n",
                       page->index);
-               desc->error = -EINVAL;
+               size = -EINVAL;
        }
 
        flush_dcache_page(p->page);
 
-       desc->count = count - size;
-       desc->written += size;
-       p->offset += size;
+       if (size > 0)
+               p->offset += size;
+
        return size;
 }
 
+static int
+lo_direct_splice_actor(struct pipe_inode_info *pipe, struct splice_desc *sd)
+{
+       return __splice_from_pipe(pipe, sd, lo_splice_actor);
+}
+
 static int
 do_lo_receive(struct loop_device *lo,
              struct bio_vec *bvec, int bsize, loff_t pos)
 {
        struct lo_read_data cookie;
+       struct splice_desc sd;
        struct file *file;
-       int retval;
+       long retval;
 
        cookie.lo = lo;
        cookie.page = bvec->bv_page;
        cookie.offset = bvec->bv_offset;
        cookie.bsize = bsize;
+
+       sd.len = 0;
+       sd.total_len = bvec->bv_len;
+       sd.flags = 0;
+       sd.pos = pos;
+       sd.u.data = &cookie;
+
        file = lo->lo_backing_file;
-       retval = file->f_op->sendfile(file, &pos, bvec->bv_len,
-                       lo_read_actor, &cookie);
-       return (retval < 0)? retval: 0;
+       retval = splice_direct_to_actor(file, &sd, lo_direct_splice_actor);
+
+       if (retval < 0)
+               return retval;
+
+       return 0;
 }
 
 static int
@@ -679,8 +703,8 @@ static int loop_change_fd(struct loop_device *lo, struct file *lo_file,
        if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
                goto out_putf;
 
-       /* new backing store needs to support loop (eg sendfile) */
-       if (!inode->i_fop->sendfile)
+       /* new backing store needs to support loop (eg splice_read) */
+       if (!inode->i_fop->splice_read)
                goto out_putf;
 
        /* size of the new backing store needs to be the same */
@@ -760,7 +784,7 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
                 * If we can't read - sorry. If we only can't write - well,
                 * it's going to be read-only.
                 */
-               if (!file->f_op->sendfile)
+               if (!file->f_op->splice_read)
                        goto out_putf;
                if (aops->prepare_write && aops->commit_write)
                        lo_flags |= LO_FLAGS_USE_AOPS;