splice: abstract out actor data

For direct splicing (or private splicing), the output may not be a file.
So abstract out the handling into a specified actor function and put
the data in the splice_desc structure earlier, so we can build on top
of that.

This is the first step in better splice handling for drivers, and also
for implementing vmsplice _to_ user memory.

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

1 files changed, 70 insertions, 29 deletions

diff --git a/fs/splice.c b/fs/splice.c
index e7d7080de2f9..68f6328236a6 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -668,31 +668,24 @@ out_ret:
  * key here is the 'actor' worker passed in that actually moves the data
  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
  */
-ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
-                           struct file *out, loff_t *ppos, size_t len,
-                           unsigned int flags, splice_actor *actor)
+ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
+                           splice_actor *actor)
 {
         int ret, do_wakeup, err;
-        struct splice_desc sd;
 
         ret = 0;
         do_wakeup = 0;
 
-        sd.total_len = len;
-        sd.flags = flags;
-        sd.file = out;
-        sd.pos = *ppos;
-
         for (;;) {
                 if (pipe->nrbufs) {
                         struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
                         const struct pipe_buf_operations *ops = buf->ops;
 
-                        sd.len = buf->len;
-                        if (sd.len > sd.total_len)
-                                sd.len = sd.total_len;
+                        sd->len = buf->len;
+                        if (sd->len > sd->total_len)
+                                sd->len = sd->total_len;
 
-                        err = actor(pipe, buf, &sd);
+                        err = actor(pipe, buf, sd);
                         if (err <= 0) {
                                 if (!ret && err != -ENODATA)
                                         ret = err;
@@ -704,10 +697,10 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
                         buf->offset += err;
                         buf->len -= err;
 
-                        sd.len -= err;
-                        sd.pos += err;
-                        sd.total_len -= err;
-                        if (sd.len)
+                        sd->len -= err;
+                        sd->pos += err;
+                        sd->total_len -= err;
+                        if (sd->len)
                                 continue;
 
                         if (!buf->len) {
@@ -719,7 +712,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
                                         do_wakeup = 1;
                         }
 
-                        if (!sd.total_len)
+                        if (!sd->total_len)
                                 break;
                 }
 
@@ -732,7 +725,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
                                 break;
                 }
 
-                if (flags & SPLICE_F_NONBLOCK) {
+                if (sd->flags & SPLICE_F_NONBLOCK) {
                         if (!ret)
                                 ret = -EAGAIN;
                         break;
@@ -772,6 +765,12 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 {
         ssize_t ret;
         struct inode *inode = out->f_mapping->host;
+        struct splice_desc sd = {
+                .total_len = len,
+                .flags = flags,
+                .pos = *ppos,
+                .file = out,
+        };
 
         /*
          * The actor worker might be calling ->prepare_write and
@@ -780,7 +779,7 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
          * pipe->inode, we have to order lock acquiry here.
          */
         inode_double_lock(inode, pipe->inode);
-        ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
+        ret = __splice_from_pipe(pipe, &sd, actor);
         inode_double_unlock(inode, pipe->inode);
 
         return ret;
@@ -804,6 +803,12 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 {
         struct address_space *mapping = out->f_mapping;
         struct inode *inode = mapping->host;
+        struct splice_desc sd = {
+                .total_len = len,
+                .flags = flags,
+                .pos = *ppos,
+                .file = out,
+        };
         ssize_t ret;
         int err;
 
@@ -811,7 +816,7 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
         if (unlikely(err))
                 return err;
 
-        ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
+        ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
         if (ret > 0) {
                 unsigned long nr_pages;
 
@@ -956,14 +961,17 @@ static long do_splice_to(struct file *in, loff_t *ppos,
         return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
 
-long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-                      size_t len, unsigned int flags)
+/*
+ * Splices from an input file to an actor, using a 'direct' pipe.
+ */
+ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
+                               splice_direct_actor *actor)
 {
         struct pipe_inode_info *pipe;
         long ret, bytes;
-        loff_t out_off;
         umode_t i_mode;
-        int i;
+        size_t len;
+        int i, flags;
 
         /*
          * We require the input being a regular file, as we don't want to
@@ -999,7 +1007,13 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
          */
         ret = 0;
         bytes = 0;
-        out_off = 0;
+        len = sd->total_len;
+        flags = sd->flags;
+
+        /*
+         * Don't block on output, we have to drain the direct pipe.
+         */
+        sd->flags &= ~SPLICE_F_NONBLOCK;
 
         while (len) {
                 size_t read_len, max_read_len;
@@ -1009,19 +1023,19 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
                  */
                 max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 
-                ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
+                ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);
                 if (unlikely(ret < 0))
                         goto out_release;
 
                 read_len = ret;
+                sd->total_len = read_len;
 
                 /*
                  * NOTE: nonblocking mode only applies to the input. We
                  * 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, &out_off, read_len,
-                                     flags & ~SPLICE_F_NONBLOCK);
+                ret = actor(pipe, sd);
                 if (unlikely(ret < 0))
                         goto out_release;
 
@@ -1066,6 +1080,33 @@ out_release:
                 return bytes;
 
         return ret;
+
+}
+EXPORT_SYMBOL(splice_direct_to_actor);
+
+static int direct_splice_actor(struct pipe_inode_info *pipe,
+                               struct splice_desc *sd)
+{
+        struct file *file = sd->file;
+
+        return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
+}
+
+long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
+                      size_t len, unsigned int flags)
+{
+        struct splice_desc sd = {
+                .len            = len,
+                .total_len      = len,
+                .flags          = flags,
+                .pos            = *ppos,
+                .file           = out,
+        };
+        size_t ret;
+
+        ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
+        *ppos = sd.pos;
+        return ret;
 }
 
 /*