[Devel] [PATCH RHEL7 COMMIT] ext4: ext4_file_dax_write() switch to iov_iter

[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 fcbb42c74c90cfdf007dac18369889ab14f34b90
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 25 17:52:34 2020 +0300

    ext4: ext4_file_dax_write() switch to iov_iter
    
    Propagate iov_iter argument into this function.
    
    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 | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 43c37e05cdb34..b617029d3016e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -216,19 +216,15 @@ ext4_file_dio_write(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
 static ssize_t
 ext4_file_dax_write(
 	struct kiocb		*iocb,
-	const struct iovec	*iovp,
-	unsigned long		nr_segs,
+	struct iov_iter		*iter,
 	loff_t			pos)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t			ret;
-	size_t			size = iov_length(iovp, nr_segs);
-	struct iov_iter iter;
-
-	iov_iter_init(&iter, iovp, nr_segs, size, 0);
+	size_t			size = iov_iter_count(iter);
 
 	inode_lock(inode);
-	ret = ext4_write_checks(iocb, &iter, &pos);
+	ret = ext4_write_checks(iocb, iter, &pos);
 	if (ret < 0)
 		goto out;
 	ret = file_remove_privs(iocb->ki_filp);
@@ -237,7 +233,7 @@ ext4_file_dax_write(
 	ret = file_update_time(iocb->ki_filp);
 	if (ret)
 		goto out;
-	ret = dax_iomap_rw(WRITE, iocb, &iter, pos,
+	ret = dax_iomap_rw(WRITE, iocb, iter, pos,
 					size, &ext4_iomap_ops);
 out:
 	inode_unlock(inode);
@@ -269,7 +265,7 @@ ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
 
 #ifdef CONFIG_FS_DAX
 	if (IS_DAX(inode))
-		return ext4_file_dax_write(iocb, iov, nr_segs, pos);
+		return ext4_file_dax_write(iocb, &iter, pos);
 #endif
 
 	iocb->private = &overwrite; /* RHEL7 only - prevent DIO race */