From: Amir Goldstein <amir73il@gmail.com>
Date: Sun, 24 Oct 2021 11:01:23 +0000 (+0300)
Subject: Add support for FOPEN_NOFLUSH flag
X-Git-Tag: fuse-3.11.0~9^2~3
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=1b498ac9b341e086562f54cc49bf035e19a94e1d;p=qemu-gpiodev%2Flibfuse.git

Add support for FOPEN_NOFLUSH flag

Allow requesting from kernel to avoid flush on close at file open
time.  If kernel does not support FOPEN_NOFLUSH flag, the request
will be ignored.

For passthrough_hp example, request to avoid flush on close when
writeback cache is disabled and file is opened O_RDONLY.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---

diff --git a/ChangeLog.rst b/ChangeLog.rst
index 521c163..96f4fb7 100644
--- a/ChangeLog.rst
+++ b/ChangeLog.rst
@@ -1,3 +1,8 @@
+Unreleased Changes
+==================
+
+* Add support for flag FOPEN_NOFLUSH for avoiding flush on close.
+
 libfuse 3.10.5 (2021-09-06)
 ===========================
 
diff --git a/example/passthrough_hp.cc b/example/passthrough_hp.cc
index 872fc73..e15f893 100644
--- a/example/passthrough_hp.cc
+++ b/example/passthrough_hp.cc
@@ -856,6 +856,7 @@ static void sfs_open(fuse_req_t req, fuse_ino_t ino, fuse_file_info *fi) {
     lock_guard<mutex> g {inode.m};
     inode.nopen++;
     fi->keep_cache = (fs.timeout != 0);
+    fi->noflush = (fs.timeout == 0 && (fi->flags & O_ACCMODE) == O_RDONLY);
     fi->fh = fd;
     fuse_reply_open(req, fi);
 }
diff --git a/include/fuse_common.h b/include/fuse_common.h
index ea4bdb0..d7481be 100644
--- a/include/fuse_common.h
+++ b/include/fuse_common.h
@@ -83,8 +83,12 @@ struct fuse_file_info {
 	    nothing when set by open()). */
 	unsigned int cache_readdir : 1;
 
+	/** Can be filled in by open, to indicate that flush is not needed
+	    on close. */
+	unsigned int noflush : 1;
+
 	/** Padding.  Reserved for future use*/
-	unsigned int padding : 25;
+	unsigned int padding : 24;
 	unsigned int padding2 : 32;
 
 	/** File handle id.  May be filled in by filesystem in create,
diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 018a00a..48f2000 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -238,12 +238,14 @@ 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
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index d227688..b5638fc 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -395,6 +395,8 @@ static void fill_open(struct fuse_open_out *arg,
 		arg->open_flags |= FOPEN_CACHE_DIR;
 	if (f->nonseekable)
 		arg->open_flags |= FOPEN_NONSEEKABLE;
+	if (f->noflush)
+		arg->open_flags |= FOPEN_NOFLUSH;
 }
 
 int fuse_reply_entry(fuse_req_t req, const struct fuse_entry_param *e)