sys_sendfile: switch to using ->splice_read, if available

This patch makes sendfile prefer to use ->splice_read(), if it's
available in the file_operations structure.

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

diff --git a/fs/read_write.c b/fs/read_write.c
index 4d03008..47da8a4 100644 (file)
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -15,6 +15,7 @@
 #include <linux/module.h>
 #include <linux/syscalls.h>
 #include <linux/pagemap.h>
+#include <linux/pipe_fs_i.h>
 #include "read_write.h"
 
 #include <asm/uaccess.h>
@@ -25,7 +26,7 @@ const struct file_operations generic_ro_fops = {
        .read           = do_sync_read,
        .aio_read       = generic_file_aio_read,
        .mmap           = generic_file_readonly_mmap,
-       .sendfile       = generic_file_sendfile,
+       .splice_read    = generic_file_splice_read,
 };
 
 EXPORT_SYMBOL(generic_ro_fops);
@@ -708,7 +709,7 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
        struct inode * in_inode, * out_inode;
        loff_t pos;
        ssize_t retval;
-       int fput_needed_in, fput_needed_out;
+       int fput_needed_in, fput_needed_out, fl;
 
        /*
         * Get input file, and verify that it is ok..
@@ -723,7 +724,8 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
        in_inode = in_file->f_path.dentry->d_inode;
        if (!in_inode)
                goto fput_in;
-       if (!in_file->f_op || !in_file->f_op->sendfile)
+       if (!in_file->f_op || (!in_file->f_op->sendfile &&
+           !in_file->f_op->splice_read))
                goto fput_in;
        retval = -ESPIPE;
        if (!ppos)
@@ -776,7 +778,21 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
                count = max - pos;
        }
 
-       retval = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
+       if (in_file->f_op->splice_read) {
+               fl = 0;
+#if 0
+               /*
+                * We need to debate whether we can enable this or not. The
+                * man page documents EAGAIN return for the output at least,
+                * and the application is arguably buggy if it doesn't expect
+                * EAGAIN on a non-blocking file descriptor.
+                */
+               if (in_file->f_flags & O_NONBLOCK)
+                       fl = SPLICE_F_NONBLOCK;
+#endif
+               retval = do_splice_direct(in_file, ppos, out_file, count, fl);
+       } else
+               retval = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
 
        if (retval > 0) {
                add_rchar(current, retval);