Add flag returned by OPENDIR request 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@xxxxxxxxxxxxxx/ Suggested-by: Miklos Szeredi <mszeredi@xxxxxxxxxx> Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx> --- Hi Miklos, I've tested this manually by watching --debug-fuse prints with and without --nocache option to passthrough_hp. The libfuse+passthrough_hp patch is at: https://github.com/amir73il/libfuse/commits/fopen_noflush Thanks, Amir. fs/fuse/file.c | 3 +++ include/uapi/linux/fuse.h | 3 +++ 2 files changed, 6 insertions(+) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 11404f8c21c7..6f502a76f9ac 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -483,6 +483,9 @@ static int fuse_flush(struct file *file, fl_owner_t id) if (fuse_is_bad(inode)) return -EIO; + if (ff->open_flags & FOPEN_NOFLUSH) + return 0; + err = write_inode_now(inode, 1); if (err) return err; diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h index 36ed092227fa..383781d1878f 100644 --- a/include/uapi/linux/fuse.h +++ b/include/uapi/linux/fuse.h @@ -184,6 +184,7 @@ * * 7.34 * - add FUSE_SYNCFS + * - add FOPEN_NOFLUSH */ #ifndef _LINUX_FUSE_H @@ -290,12 +291,14 @@ 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 every close */ #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 -- 2.25.1
