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>

1 files changed, 44 insertions, 20 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 0ed5470d2533..87d84e7d5432 100644
--- 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;