The patch titled
Subject: fs: factor out a direct_write_fallback helper
has been added to the -mm mm-unstable branch. Its filename is
fs-factor-out-a-direct_write_fallback-helper.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-factor-out-a-direct_write_fallback-helper.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Christoph Hellwig <hch@xxxxxx>
Subject: fs: factor out a direct_write_fallback helper
Date: Fri, 19 May 2023 11:35:18 +0200
Add a helper dealing with handling the syncing of a buffered write
fallback for direct I/O.
Link: https://lkml.kernel.org/r/20230519093521.133226-11-hch@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Cc: Anna Schumaker <anna@xxxxxxxxxx>
Cc: Chao Yu <chao@xxxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Damien Le Moal <dlemoal@xxxxxxxxxx>
Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
Cc: Ilya Dryomov <idryomov@xxxxxxxxx>
Cc: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Cc: Xiubo Li <xiubli@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/libfs.c | 36 ++++++++++++++++++++++++++
include/linux/fs.h | 2 +
mm/filemap.c | 59 ++++++++-----------------------------------
3 files changed, 50 insertions(+), 47 deletions(-)
--- a/fs/libfs.c~fs-factor-out-a-direct_write_fallback-helper
+++ a/fs/libfs.c
@@ -1613,3 +1613,39 @@ u64 inode_query_iversion(struct inode *i
return cur >> I_VERSION_QUERIED_SHIFT;
}
EXPORT_SYMBOL(inode_query_iversion);
+
+ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
+ ssize_t direct_written, ssize_t buffered_written)
+{
+ struct address_space *mapping = iocb->ki_filp->f_mapping;
+ loff_t pos = iocb->ki_pos, end;
+ int err;
+
+ /*
+ * If the buffered write fallback returned an error, we want to return
+ * the number of bytes which were written by direct I/O, or the error
+ * code if that was zero.
+ *
+ * Note that this differs from normal direct-io semantics, which will
+ * return -EFOO even if some bytes were written.
+ */
+ if (unlikely(buffered_written < 0))
+ return buffered_written;
+
+ /*
+ * We need to ensure that the page cache pages are written to disk and
+ * invalidated to preserve the expected O_DIRECT semantics.
+ */
+ end = pos + buffered_written - 1;
+ err = filemap_write_and_wait_range(mapping, pos, end);
+ if (err < 0) {
+ /*
+ * We don't know how much we wrote, so just return the number of
+ * bytes which were direct-written
+ */
+ return err;
+ }
+ invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT, end >> PAGE_SHIFT);
+ return direct_written + buffered_written;
+}
+EXPORT_SYMBOL_GPL(direct_write_fallback);
--- a/include/linux/fs.h~fs-factor-out-a-direct_write_fallback-helper
+++ a/include/linux/fs.h
@@ -2738,6 +2738,8 @@ extern ssize_t __generic_file_write_iter
extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
extern ssize_t generic_file_direct_write(struct kiocb *, struct iov_iter *);
ssize_t generic_perform_write(struct kiocb *, struct iov_iter *);
+ssize_t direct_write_fallback(struct kiocb *iocb, struct iov_iter *iter,
+ ssize_t direct_written, ssize_t buffered_written);
ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos,
rwf_t flags);
--- a/mm/filemap.c~fs-factor-out-a-direct_write_fallback-helper
+++ a/mm/filemap.c
@@ -3981,25 +3981,21 @@ ssize_t __generic_file_write_iter(struct
{
struct file *file = iocb->ki_filp;
struct address_space *mapping = file->f_mapping;
- struct inode *inode = mapping->host;
- ssize_t written = 0;
- ssize_t err;
- ssize_t status;
+ struct inode *inode = mapping->host;
+ ssize_t ret;
/* We can write back this queue in page reclaim */
current->backing_dev_info = inode_to_bdi(inode);
- err = file_remove_privs(file);
- if (err)
+ ret = file_remove_privs(file);
+ if (ret)
goto out;
- err = file_update_time(file);
- if (err)
+ ret = file_update_time(file);
+ if (ret)
goto out;
if (iocb->ki_flags & IOCB_DIRECT) {
- loff_t pos, endbyte;
-
- written = generic_file_direct_write(iocb, from);
+ ret = generic_file_direct_write(iocb, from);
/*
* If the write stopped short of completing, fall back to
* buffered writes. Some filesystems do this for writes to
@@ -4007,46 +4003,15 @@ ssize_t __generic_file_write_iter(struct
* not succeed (even if it did, DAX does not handle dirty
* page-cache pages correctly).
*/
- if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
- goto out;
-
- pos = iocb->ki_pos;
- status = generic_perform_write(iocb, from);
- /*
- * If generic_perform_write() returned a synchronous error
- * then we want to return the number of bytes which were
- * direct-written, or the error code if that was zero. Note
- * that this differs from normal direct-io semantics, which
- * will return -EFOO even if some bytes were written.
- */
- if (unlikely(status < 0)) {
- err = status;
- goto out;
- }
- /*
- * We need to ensure that the page cache pages are written to
- * disk and invalidated to preserve the expected O_DIRECT
- * semantics.
- */
- endbyte = pos + status - 1;
- err = filemap_write_and_wait_range(mapping, pos, endbyte);
- if (err == 0) {
- written += status;
- invalidate_mapping_pages(mapping,
- pos >> PAGE_SHIFT,
- endbyte >> PAGE_SHIFT);
- } else {
- /*
- * We don't know how much we wrote, so just return
- * the number of bytes which were direct-written
- */
- }
+ if (ret >= 0 && iov_iter_count(from) && !IS_DAX(inode))
+ ret = direct_write_fallback(iocb, from, ret,
+ generic_perform_write(iocb, from));
} else {
- written = generic_perform_write(iocb, from);
+ ret = generic_perform_write(iocb, from);
}
out:
current->backing_dev_info = NULL;
- return written ? written : err;
+ return ret;
}
EXPORT_SYMBOL(__generic_file_write_iter);
_
Patches currently in -mm which might be from hch@xxxxxx are
iomap-update-ki_pos-a-little-later-in-iomap_dio_complete.patch
filemap-update-ki_pos-in-generic_perform_write.patch
filemap-assign-current-backing_dev_info-in-generic_perform_write.patch
filemap-add-a-kiocb_write_and_wait-helper.patch
filemap-add-a-kiocb_invalidate_pages-helper.patch
filemap-add-a-kiocb_invalidate_post_write-helper.patch
iomap-update-ki_pos-in-iomap_file_buffered_write.patch
iomap-assign-current-backing_dev_info-in-iomap_file_buffered_write.patch
iomap-use-kiocb_write_and_wait-and-kiocb_invalidate_pages.patch
fs-factor-out-a-direct_write_fallback-helper.patch
fuse-update-ki_pos-in-fuse_perform_write.patch
fuse-drop-redundant-arguments-to-fuse_perform_write.patch
fuse-use-direct_write_fallback.patch
squashfs-dont-include-buffer_headh.patch
