[Devel] [PATCH RHEL7 COMMIT] fs: More use iov_iter in ext4_file_write()

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-1127.8.2.vz7.161.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.8.2.vz7.161.1
------>
commit ea3e15dc5854e937ade593884d760f3d2807ea46
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 25 17:52:33 2020 +0300

    fs: More use iov_iter in ext4_file_write()
    
    1)After iov_iter is added as local variable at start
     of this function, we should not introduce it again
     for ext4_file_dio_write().
    
    2)Instead of generic_file_aio_write() we use its
    iov_iter variant generic_file_write_iter()
    
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    =====================
    Patchset description:
    [00/30] fs,direct_IO: Switch to iov_iter and allow bio_vec for ext4
    
    This patchset transforms direct_IO callbacks, blockdev_direct_IO
    and its underlining functions to iov_iter, and introduces complete
    support of iov_iter for ext4.
    
    Supported iov_iter subtypes for ext4 is iovec and bio_vec. The first
    is for traditional user-submitted aio, while bio_vec is the type,
    which is important for us, since we use it in ploop.
    
    bio_vec operates with pages instead of user addresses (like iovec
    does), so it requires specific callbacks in do_blockdev_direct_IO()
    and in the functions it calls.
    
    The patchset reworks do_blockdev_direct_IO() in the same manner
    as in mainstrean. The most of rest patches are prepared manually,
    since we have significant differences to ms (RHEL7 patches, our
    direct IO patches for FUSE; all they have changed many functions).
    At the end, kaio engine (resulting in direct_IO) became possible
    to be enabled for ext4.
    
    https://jira.sw.ru/browse/PSBM-99793
---
 fs/ext4/file.c | 10 +++-------
 1 file changed, 3 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 36622e82d152f..43c37e05cdb34 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -273,14 +273,10 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 #endif
 
 	iocb->private = &overwrite; /* RHEL7 only - prevent DIO race */
-	if (unlikely(io_is_direct(iocb->ki_filp))) {
-		struct iov_iter iter;
-
-		iov_iter_init(&iter, iov, nr_segs, iov_length(iov, nr_segs), 0);
-
+	if (unlikely(io_is_direct(iocb->ki_filp)))
 		ret = ext4_file_dio_write(iocb, &iter, pos);
-	} else
-		ret = generic_file_aio_write(iocb, iov, nr_segs, pos);
+	else
+		ret = generic_file_write_iter(iocb, &iter, pos);
 
 	return ret;
 }