[PATCH 1/4] libfuse: wire up FUSE_SYNCFS to the low level library

["Darrick J. Wong" <djwong@xxxxxxxxxx>]

From: Darrick J. Wong <djwong@xxxxxxxxxx>

Create hooks in the lowlevel library for syncfs.

Signed-off-by: "Darrick J. Wong" <djwong@xxxxxxxxxx>
---
 include/fuse_lowlevel.h |   16 ++++++++++++++++
 lib/fuse_lowlevel.c     |   19 +++++++++++++++++++
 2 files changed, 35 insertions(+)


diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index f690c62fcdd61c..77685e433e4f7d 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -1400,6 +1400,22 @@ struct fuse_lowlevel_ops {
 	 * @param maxbytes maximum supported file size
 	 */
 	void (*iomap_config) (fuse_req_t req, uint32_t flags, int64_t maxbytes);
+
+	/**
+	 * Flush the entire filesystem to disk.
+	 *
+	 * If this request is answered with an error code of ENOSYS, this is
+	 * treated as a permanent failure, i.e. all future syncfs() requests
+	 * will fail with the same error code without being sent to the
+	 * filesystem process.
+	 *
+	 * Valid replies:
+	 *   fuse_reply_err
+	 *
+	 * @param req request handle
+	 * @param ino the inode number
+	 */
+	void (*syncfs) (fuse_req_t req, fuse_ino_t ino);
 #endif /* FUSE_USE_VERSION >= 318 */
 };
 
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index e31ce96593a9b3..ec30ebc4cdd074 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -2636,6 +2636,23 @@ static void do_iomap_config(fuse_req_t req, const fuse_ino_t nodeid,
 	_do_iomap_config(req, nodeid, inarg, NULL);
 }
 
+static void _do_syncfs(fuse_req_t req, const fuse_ino_t nodeid,
+		      const void *op_in, const void *in_payload)
+{
+	(void)op_in;
+	(void)in_payload;
+
+	if (req->se->op.syncfs)
+		req->se->op.syncfs(req, nodeid);
+	else
+		fuse_reply_err(req, ENOSYS);
+}
+
+static void do_syncfs(fuse_req_t req, const fuse_ino_t nodeid, const void *inarg)
+{
+	_do_syncfs(req, nodeid, inarg, NULL);
+}
+
 static bool want_flags_valid(uint64_t capable, uint64_t want)
 {
 	uint64_t unknown_flags = want & (~capable);
@@ -3609,6 +3626,7 @@ static struct {
 	[FUSE_RENAME2]     = { do_rename2,      "RENAME2"    },
 	[FUSE_COPY_FILE_RANGE] = { do_copy_file_range, "COPY_FILE_RANGE" },
 	[FUSE_LSEEK]	   = { do_lseek,       "LSEEK"	     },
+	[FUSE_SYNCFS]	   = { do_syncfs,	"SYNCFS"     },
 	[FUSE_IOMAP_CONFIG]= { do_iomap_config, "IOMAP_CONFIG" },
 	[FUSE_IOMAP_BEGIN] = { do_iomap_begin,	"IOMAP_BEGIN" },
 	[FUSE_IOMAP_END]   = { do_iomap_end,	"IOMAP_END" },
@@ -3667,6 +3685,7 @@ static struct {
 	[FUSE_RENAME2]		= { _do_rename2,	"RENAME2" },
 	[FUSE_COPY_FILE_RANGE]	= { _do_copy_file_range, "COPY_FILE_RANGE" },
 	[FUSE_LSEEK]		= { _do_lseek,		"LSEEK" },
+	[FUSE_SYNCFS]		= { _do_syncfs,		"SYNCFS" },
 	[FUSE_IOMAP_CONFIG]	= { _do_iomap_config,	"IOMAP_CONFIG" },
 	[FUSE_IOMAP_BEGIN]	= { _do_iomap_begin,	"IOMAP_BEGIN" },
 	[FUSE_IOMAP_END]	= { _do_iomap_end,	"IOMAP_END" },