[PATCH] splice: fix offset problems

Make the move_from_pipe() actors return number of bytes processed, then
move_from_pipe() can decide more cleverly when to move on to the next
buffer.

This fixes problems with pipe offset and differing file offset.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 27 insertions, 19 deletions

diff --git a/fs/splice.c b/fs/splice.c
index 4aa67254740f..8c6030c762e2 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -439,14 +439,13 @@ EXPORT_SYMBOL(generic_file_splice_read);
 
 /*
  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
- * using sendpage().
+ * using sendpage(). Return the number of bytes sent.
  */
 static int pipe_to_sendpage(struct pipe_inode_info *info,
                             struct pipe_buffer *buf, struct splice_desc *sd)
 {
         struct file *file = sd->file;
         loff_t pos = sd->pos;
-        unsigned int offset;
         ssize_t ret;
         void *ptr;
         int more;
@@ -461,16 +460,13 @@ static int pipe_to_sendpage(struct pipe_inode_info *info,
         if (IS_ERR(ptr))
                 return PTR_ERR(ptr);
 
-        offset = pos & ~PAGE_CACHE_MASK;
         more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
 
-        ret = file->f_op->sendpage(file, buf->page, offset, sd->len, &pos,more);
+        ret = file->f_op->sendpage(file, buf->page, buf->offset, sd->len,
+                                   &pos, more);
 
         buf->ops->unmap(info, buf);
-        if (ret == sd->len)
-                return 0;
-
-        return -EIO;
+        return ret;
 }
 
 /*
@@ -499,7 +495,7 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
         struct file *file = sd->file;
         struct address_space *mapping = file->f_mapping;
         gfp_t gfp_mask = mapping_gfp_mask(mapping);
-        unsigned int offset;
+        unsigned int offset, this_len;
         struct page *page;
         pgoff_t index;
         char *src;
@@ -515,6 +511,10 @@ static int pipe_to_file(struct pipe_inode_info *info, struct pipe_buffer *buf,
         index = sd->pos >> PAGE_CACHE_SHIFT;
         offset = sd->pos & ~PAGE_CACHE_MASK;
 
+        this_len = sd->len;
+        if (this_len + offset > PAGE_CACHE_SIZE)
+                this_len = PAGE_CACHE_SIZE - offset;
+
         /*
          * Reuse buf page, if SPLICE_F_MOVE is set.
          */
@@ -558,7 +558,7 @@ find_page:
                  * the full page.
                  */
                 if (!PageUptodate(page)) {
-                        if (sd->len < PAGE_CACHE_SIZE) {
+                        if (this_len < PAGE_CACHE_SIZE) {
                                 ret = mapping->a_ops->readpage(file, page);
                                 if (unlikely(ret))
                                         goto out;
@@ -582,7 +582,7 @@ find_page:
                 }
         }
 
-        ret = mapping->a_ops->prepare_write(file, page, 0, sd->len);
+        ret = mapping->a_ops->prepare_write(file, page, offset, offset+this_len);
         if (ret == AOP_TRUNCATED_PAGE) {
                 page_cache_release(page);
                 goto find_page;
@@ -592,18 +592,22 @@ find_page:
         if (!(buf->flags & PIPE_BUF_FLAG_STOLEN)) {
                 char *dst = kmap_atomic(page, KM_USER0);
 
-                memcpy(dst + offset, src + buf->offset, sd->len);
+                memcpy(dst + offset, src + buf->offset, this_len);
                 flush_dcache_page(page);
                 kunmap_atomic(dst, KM_USER0);
         }
 
-        ret = mapping->a_ops->commit_write(file, page, 0, sd->len);
+        ret = mapping->a_ops->commit_write(file, page, offset, offset+this_len);
         if (ret == AOP_TRUNCATED_PAGE) {
                 page_cache_release(page);
                 goto find_page;
         } else if (ret)
                 goto out;
 
+        /*
+         * Return the number of bytes written.
+         */
+        ret = this_len;
         mark_page_accessed(page);
         balance_dirty_pages_ratelimited(mapping);
 out:
@@ -652,16 +656,22 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                                 sd.len = sd.total_len;
 
                         err = actor(pipe, buf, &sd);
-                        if (err) {
+                        if (err <= 0) {
                                 if (!ret && err != -ENODATA)
                                         ret = err;
 
                                 break;
                         }
 
-                        ret += sd.len;
-                        buf->offset += sd.len;
-                        buf->len -= sd.len;
+                        ret += err;
+                        buf->offset += err;
+                        buf->len -= err;
+
+                        sd.len -= err;
+                        sd.pos += err;
+                        sd.total_len -= err;
+                        if (sd.len)
+                                continue;
 
                         if (!buf->len) {
                                 buf->ops = NULL;
@@ -672,8 +682,6 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                                         do_wakeup = 1;
                         }
 
-                        sd.pos += sd.len;
-                        sd.total_len -= sd.len;
                         if (!sd.total_len)
                                 break;
                 }