Commit a390ccb3 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
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fuse: add FOPEN_NOFLUSH 

Add flag returned by FUSE_OPEN and FUSE_CREATE requests to avoid flushing
data cache on close.

Different filesystems implement ->flush() is different ways:
 - Most disk filesystems do not implement ->flush() at all
 - Some network filesystem (e.g. nfs) flush local write cache of
   FMODE_WRITE file and send a "flush" command to server
 - Some network filesystem (e.g. cifs) flush local write cache of
   FMODE_WRITE file without sending an additional command to server

FUSE flushes local write cache of ANY file, even non FMODE_WRITE
and sends a "flush" command to server (if server implements it).

The FUSE implementation of ->flush() seems over agressive and
arbitrary and does not make a lot of sense when writeback caching is
disabled.

Instead of deciding on another arbitrary implementation that makes
sense, leave the choice of per-file flush behavior in the hands of
the server.

Link: https://lore.kernel.org/linux-fsdevel/CAJfpegspE8e6aKd47uZtSYX8Y-1e1FWS0VL0DH2Skb9gQP5RJQ@mail.gmail.com/


Suggested-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent c6c745b8

fs/fuse/file.c

+3 −0
Original line number Diff line number Diff line
@@ -476,6 +476,9 @@ static int fuse_flush(struct file *file, fl_owner_t id) 
	if (fuse_is_bad(inode))

		return -EIO;



	if (ff->open_flags & FOPEN_NOFLUSH && !fm->fc->writeback_cache)

		return 0;



	err = write_inode_now(inode, 1);

	if (err)

		return err;

include/uapi/linux/fuse.h

+6 −1
Original line number Diff line number Diff line
@@ -184,6 +184,9 @@ 
 *

 *  7.34

 *  - add FUSE_SYNCFS

 *

 *  7.35

 *  - add FOPEN_NOFLUSH

 */



#ifndef _LINUX_FUSE_H
@@ -219,7 +222,7 @@ 
#define FUSE_KERNEL_VERSION 7



/** Minor version number of this interface */

#define FUSE_KERNEL_MINOR_VERSION 34

#define FUSE_KERNEL_MINOR_VERSION 35



/** The node ID of the root inode */

#define FUSE_ROOT_ID 1
@@ -290,12 +293,14 @@ struct fuse_file_lock { 
 * FOPEN_NONSEEKABLE: the file is not seekable

 * FOPEN_CACHE_DIR: allow caching this directory

 * FOPEN_STREAM: the file is stream-like (no file position at all)

 * FOPEN_NOFLUSH: don't flush data cache on close (unless FUSE_WRITEBACK_CACHE)

 */

#define FOPEN_DIRECT_IO		(1 << 0)

#define FOPEN_KEEP_CACHE	(1 << 1)

#define FOPEN_NONSEEKABLE	(1 << 2)

#define FOPEN_CACHE_DIR		(1 << 3)

#define FOPEN_STREAM		(1 << 4)

#define FOPEN_NOFLUSH		(1 << 5)



/**

 * INIT request/reply flags