[Devel] [PATCH RHEL7 COMMIT] ext4: Introduce ext4_file_write_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 41e7c727f48ce4026d4f46392c344f354e947a62
Author: Kirill Tkhai <ktkhai at virtuozzo.com>
Date:   Mon May 25 17:52:35 2020 +0300

    ext4: Introduce ext4_file_write_iter()
    
    Move all functionality from ext4_file_write()
    to separate function. ext4_file_write() now
    contains only iov_iter initialization.
    
    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 | 25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index b617029d3016e..32b17c61b52b3 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -249,34 +249,41 @@ ext4_file_dax_write(
 #endif
 
 static ssize_t
-ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
-		unsigned long nr_segs, loff_t pos)
+ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *iter, loff_t pos)
 {
 	struct inode *inode = file_inode(iocb->ki_filp);
 	ssize_t ret;
 	int overwrite = 0;
-	struct iov_iter iter;
-
-	iov_iter_init(&iter, iov, nr_segs, iov_length(iov, nr_segs), 0);
 
-	ret = ext4_write_checks(iocb, &iter, &pos);
+	ret = ext4_write_checks(iocb, iter, &pos);
 	if (ret <= 0)
 		return ret;
 
 #ifdef CONFIG_FS_DAX
 	if (IS_DAX(inode))
-		return ext4_file_dax_write(iocb, &iter, pos);
+		return ext4_file_dax_write(iocb, iter, pos);
 #endif
 
 	iocb->private = &overwrite; /* RHEL7 only - prevent DIO race */
 	if (unlikely(io_is_direct(iocb->ki_filp)))
-		ret = ext4_file_dio_write(iocb, &iter, pos);
+		ret = ext4_file_dio_write(iocb, iter, pos);
 	else
-		ret = generic_file_write_iter(iocb, &iter, pos);
+		ret = generic_file_write_iter(iocb, iter, pos);
 
 	return ret;
 }
 
+static ssize_t
+ext4_file_write(struct kiocb *iocb, const struct iovec *iov,
+		unsigned long nr_segs, loff_t pos)
+{
+	struct iov_iter iter;
+
+	iov_iter_init(&iter, iov, nr_segs, iov_length(iov, nr_segs), 0);
+
+	return ext4_file_write_iter(iocb, &iter, pos);
+}
+
 #ifdef CONFIG_FS_DAX
 static int ext4_dax_huge_fault(struct vm_fault *vmf,
 		enum page_entry_size pe_size)