[PATCH] splice: pass offset around for ->splice_read() and ->splice_write()

We need not use ->f_pos as the offset for the file input/output. If the
user passed an offset pointer in through sys_splice(), just use that and
leave ->f_pos alone.

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

1 files changed, 44 insertions, 42 deletions

diff --git a/fs/splice.c b/fs/splice.c
index e50a460239dd..5d3eda64703b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -231,8 +231,9 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
 }
 
 static int
-__generic_file_splice_read(struct file *in, struct pipe_inode_info *pipe,
-                           size_t len, unsigned int flags)
+__generic_file_splice_read(struct file *in, loff_t *ppos,
+                           struct pipe_inode_info *pipe, size_t len,
+                           unsigned int flags)
 {
         struct address_space *mapping = in->f_mapping;
         unsigned int offset, nr_pages;
@@ -241,8 +242,8 @@ __generic_file_splice_read(struct file *in, struct pipe_inode_info *pipe,
         pgoff_t index;
         int i, error;
 
-        index = in->f_pos >> PAGE_CACHE_SHIFT;
-        offset = in->f_pos & ~PAGE_CACHE_MASK;
+        index = *ppos >> PAGE_CACHE_SHIFT;
+        offset = *ppos & ~PAGE_CACHE_MASK;
         nr_pages = (len + offset + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
 
         if (nr_pages > PIPE_BUFFERS)
@@ -348,8 +349,9 @@ fill_it:
  *
  * Will read pages from given file and fill them into a pipe.
  */
-ssize_t generic_file_splice_read(struct file *in, struct pipe_inode_info *pipe,
-                                 size_t len, unsigned int flags)
+ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
+                                 struct pipe_inode_info *pipe, size_t len,
+                                 unsigned int flags)
 {
         ssize_t spliced;
         int ret;
@@ -358,12 +360,12 @@ ssize_t generic_file_splice_read(struct file *in, struct pipe_inode_info *pipe,
         spliced = 0;
 
         while (len) {
-                ret = __generic_file_splice_read(in, pipe, len, flags);
+                ret = __generic_file_splice_read(in, ppos, pipe, len, flags);
 
                 if (ret <= 0)
                         break;
 
-                in->f_pos += ret;
+                *ppos += ret;
                 len -= ret;
                 spliced += ret;
 
@@ -561,7 +563,7 @@ typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
  */
 static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
-                              size_t len, unsigned int flags,
+                              loff_t *ppos, size_t len, unsigned int flags,
                               splice_actor *actor)
 {
         int ret, do_wakeup, err;
@@ -573,7 +575,7 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
         sd.total_len = len;
         sd.flags = flags;
         sd.file = out;
-        sd.pos = out->f_pos;
+        sd.pos = *ppos;
 
         if (pipe->inode)
                 mutex_lock(&pipe->inode->i_mutex);
@@ -656,9 +658,7 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
         }
 
-        out->f_pos = sd.pos;
         return ret;
-
 }
 
 /**
@@ -674,12 +674,12 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
  */
 ssize_t
 generic_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
-                          size_t len, unsigned int flags)
+                          loff_t *ppos, size_t len, unsigned int flags)
 {
         struct address_space *mapping = out->f_mapping;
         ssize_t ret;
 
-        ret = move_from_pipe(pipe, out, len, flags, pipe_to_file);
+        ret = move_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
 
         /*
          * If file or inode is SYNC and we actually wrote some data, sync it.
@@ -715,9 +715,9 @@ EXPORT_SYMBOL(generic_file_splice_write);
  *
  */
 ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe, struct file *out,
-                                size_t len, unsigned int flags)
+                                loff_t *ppos, size_t len, unsigned int flags)
 {
-        return move_from_pipe(pipe, out, len, flags, pipe_to_sendpage);
+        return move_from_pipe(pipe, out, ppos, len, flags, pipe_to_sendpage);
 }
 
 EXPORT_SYMBOL(generic_splice_sendpage);
@@ -726,9 +726,8 @@ EXPORT_SYMBOL(generic_splice_sendpage);
  * Attempt to initiate a splice from pipe to file.
  */
 static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
-                           size_t len, unsigned int flags)
+                           loff_t *ppos, size_t len, unsigned int flags)
 {
-        loff_t pos;
         int ret;
 
         if (unlikely(!out->f_op || !out->f_op->splice_write))
@@ -737,22 +736,21 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
         if (unlikely(!(out->f_mode & FMODE_WRITE)))
                 return -EBADF;
 
-        pos = out->f_pos;
-
-        ret = rw_verify_area(WRITE, out, &pos, len);
+        ret = rw_verify_area(WRITE, out, ppos, len);
         if (unlikely(ret < 0))
                 return ret;
 
-        return out->f_op->splice_write(pipe, out, len, flags);
+        return out->f_op->splice_write(pipe, out, ppos, len, flags);
 }
 
 /*
  * Attempt to initiate a splice from a file to a pipe.
  */
-static long do_splice_to(struct file *in, struct pipe_inode_info *pipe,
-                         size_t len, unsigned int flags)
+static long do_splice_to(struct file *in, loff_t *ppos,
+                         struct pipe_inode_info *pipe, size_t len,
+                         unsigned int flags)
 {
-        loff_t pos, isize, left;
+        loff_t isize, left;
         int ret;
 
         if (unlikely(!in->f_op || !in->f_op->splice_read))
@@ -761,28 +759,27 @@ static long do_splice_to(struct file *in, struct pipe_inode_info *pipe,
         if (unlikely(!(in->f_mode & FMODE_READ)))
                 return -EBADF;
 
-        pos = in->f_pos;
-
-        ret = rw_verify_area(READ, in, &pos, len);
+        ret = rw_verify_area(READ, in, ppos, len);
         if (unlikely(ret < 0))
                 return ret;
 
         isize = i_size_read(in->f_mapping->host);
-        if (unlikely(in->f_pos >= isize))
+        if (unlikely(*ppos >= isize))
                 return 0;
         
-        left = isize - in->f_pos;
+        left = isize - *ppos;
         if (unlikely(left < len))
                 len = left;
 
-        return in->f_op->splice_read(in, pipe, len, flags);
+        return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
 
-long do_splice_direct(struct file *in, struct file *out, size_t len,
-                      unsigned int flags)
+long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
+                      size_t len, unsigned int flags)
 {
         struct pipe_inode_info *pipe;
         long ret, bytes;
+        loff_t out_off;
         umode_t i_mode;
         int i;
 
@@ -820,6 +817,7 @@ long do_splice_direct(struct file *in, struct file *out, size_t len,
          */
         ret = 0;
         bytes = 0;
+        out_off = 0;
 
         while (len) {
                 size_t read_len, max_read_len;
@@ -829,7 +827,7 @@ long do_splice_direct(struct file *in, struct file *out, size_t len,
                  */
                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 
-                ret = do_splice_to(in, pipe, max_read_len, flags);
+                ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
                 if (unlikely(ret < 0))
                         goto out_release;
 
@@ -840,7 +838,7 @@ long do_splice_direct(struct file *in, struct file *out, size_t len,
                  * must not do the output in nonblocking mode as then we
                  * could get stuck data in the internal pipe:
                  */
-                ret = do_splice_from(pipe, out, read_len,
+                ret = do_splice_from(pipe, out, &out_off, read_len,
                                      flags & ~SPLICE_F_NONBLOCK);
                 if (unlikely(ret < 0))
                         goto out_release;
@@ -898,6 +896,7 @@ static long do_splice(struct file *in, loff_t __user *off_in,
                       size_t len, unsigned int flags)
 {
         struct pipe_inode_info *pipe;
+        loff_t offset, *off;
 
         pipe = in->f_dentry->d_inode->i_pipe;
         if (pipe) {
@@ -906,12 +905,13 @@ static long do_splice(struct file *in, loff_t __user *off_in,
                 if (off_out) {
                         if (out->f_op->llseek == no_llseek)
                                 return -EINVAL;
-                        if (copy_from_user(&out->f_pos, off_out,
-                                           sizeof(loff_t)))
+                        if (copy_from_user(&offset, off_out, sizeof(loff_t)))
                                 return -EFAULT;
-                }
+                        off = &offset;
+                } else
+                        off = &out->f_pos;
 
-                return do_splice_from(pipe, out, len, flags);
+                return do_splice_from(pipe, out, off, len, flags);
         }
 
         pipe = out->f_dentry->d_inode->i_pipe;
@@ -921,11 +921,13 @@ static long do_splice(struct file *in, loff_t __user *off_in,
                 if (off_in) {
                         if (in->f_op->llseek == no_llseek)
                                 return -EINVAL;
-                        if (copy_from_user(&in->f_pos, off_in, sizeof(loff_t)))
+                        if (copy_from_user(&offset, off_in, sizeof(loff_t)))
                                 return -EFAULT;
-                }
+                        off = &offset;
+                } else
+                        off = &in->f_pos;
 
-                return do_splice_to(in, pipe, len, flags);
+                return do_splice_to(in, off, pipe, len, flags);
         }
 
         return -EINVAL;