splice: implement default splice_read method

If f_op->splice_read() is not implemented, fall back to a plain read.
Use vfs_readv() to read into previously allocated pages.

This will allow splice and functions using splice, such as the loop
device, to work on all filesystems.  This includes "direct_io" files
in fuse which bypass the page cache.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/fs/coda/file.c b/fs/coda/file.c
index 6a347fbc998a..ffd42815fda1 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -47,6 +47,8 @@ coda_file_splice_read(struct file *coda_file, loff_t *ppos,
                       struct pipe_inode_info *pipe, size_t count,
                       unsigned int flags)
 {
+        ssize_t (*splice_read)(struct file *, loff_t *,
+                               struct pipe_inode_info *, size_t, unsigned int);
         struct coda_file_info *cfi;
         struct file *host_file;
 
@@ -54,10 +56,11 @@ coda_file_splice_read(struct file *coda_file, loff_t *ppos,
         BUG_ON(!cfi || cfi->cfi_magic != CODA_MAGIC);
         host_file = cfi->cfi_container;
 
-        if (!host_file->f_op || !host_file->f_op->splice_read)
-                return -EINVAL;
+        splice_read = host_file->f_op->splice_read;
+        if (!splice_read)
+                splice_read = default_file_splice_read;
 
-        return host_file->f_op->splice_read(host_file, ppos, pipe, count,flags);
+        return splice_read(host_file, ppos, pipe, count, flags);
 }
 
 static ssize_t