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>
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 9ca4bb0..801f4ab 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -709,10 +709,6 @@
if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
goto out_putf;
- /* 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 */
if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
goto out_putf;
@@ -788,12 +784,7 @@
error = -EINVAL;
if (S_ISREG(inode->i_mode) || S_ISBLK(inode->i_mode)) {
const struct address_space_operations *aops = mapping->a_ops;
- /*
- * If we can't read - sorry. If we only can't write - well,
- * it's going to be read-only.
- */
- if (!file->f_op->splice_read)
- goto out_putf;
+
if (aops->write_begin)
lo_flags |= LO_FLAGS_USE_AOPS;
if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)