[PATCH v1 02/14] mm: Introduce do_generic_perform_write

Stefan Roesch
2022-02-14T17:44:35Z

This splits off the do generic_perform_write() function, so an
additional flags parameter can be specified. It uses the new flag
parameter to support async buffered writes.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
include/linux/fs.h | 1 +
mm/filemap.c | 20 +++++++++++++++-----
2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e2d892b201b0..e62dba6ed453 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -278,6 +278,7 @@ enum positive_aop_returns {
#define AOP_FLAG_NOFS 0x0002 /* used by filesystem to direct
* helper code (eg buffer layer)
* to clear GFP_FS from alloc */
+#define AOP_FLAGS_NOWAIT 0x0004 /* async nowait buffered writes */

/*
* oh the beauties of C type declarations.
diff --git a/mm/filemap.c b/mm/filemap.c
index ad8c39d90bf9..d2fb817c0845 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -3725,14 +3725,13 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from)
}
EXPORT_SYMBOL(generic_file_direct_write);

-ssize_t generic_perform_write(struct file *file,
- struct iov_iter *i, loff_t pos)
+static ssize_t do_generic_perform_write(struct file *file, struct iov_iter *i,
+ loff_t pos, int flags)
{
struct address_space *mapping = file->f_mapping;
const struct address_space_operations *a_ops = mapping->a_ops;
long status = 0;
ssize_t written = 0;
- unsigned int flags = 0;

do {
struct page *page;
@@ -3801,6 +3800,12 @@ ssize_t generic_perform_write(struct file *file,

return written ? written : status;
}
+
+ssize_t generic_perform_write(struct file *file,
+ struct iov_iter *i, loff_t pos)
+{
+ return do_generic_perform_write(file, i, pos, 0);
+}
EXPORT_SYMBOL(generic_perform_write);

/**
@@ -3832,6 +3837,10 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
ssize_t written = 0;
ssize_t err;
ssize_t status;
+ int flags = 0;
+
+ if (iocb->ki_flags & IOCB_NOWAIT)
+ flags |= AOP_FLAGS_NOWAIT;

/* We can write back this queue in page reclaim */
current->backing_dev_info = inode_to_bdi(inode);
@@ -3857,7 +3866,8 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (written < 0 || !iov_iter_count(from) || IS_DAX(inode))
goto out;

- status = generic_perform_write(file, from, pos = iocb->ki_pos);
+ status = do_generic_perform_write(file, from, pos = iocb->ki_pos, flags);
+
/*
* If generic_perform_write() returned a synchronous error
* then we want to return the number of bytes which were
@@ -3889,7 +3899,7 @@ ssize_t __generic_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
*/
}
} else {
- written = generic_perform_write(file, from, iocb->ki_pos);
+ written = do_generic_perform_write(file, from, iocb->ki_pos, flags);
if (likely(written > 0))
iocb->ki_pos += written;
}
--
2.30.2