[PATCH 18/25] libfuse: add low level code to invalidate iomap block device ranges

["Darrick J. Wong" <djwong@kernel.org>]

From: Darrick J. Wong <djwong@kernel.org>

Make it easier to invalidate the page cache for a block device that is
being used in conjunction with iomap.  This allows a fuse server to kill
all cached data for a block that is being freed, so that block reuse
doesn't result in file corruption.

Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
---
 include/fuse_kernel.h   |   15 +++++++++++++++
 include/fuse_lowlevel.h |   15 +++++++++++++++
 lib/fuse_lowlevel.c     |   22 ++++++++++++++++++++++
 lib/fuse_versionscript  |    1 +
 4 files changed, 53 insertions(+)


diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 897d996a0ce60d..1e7c9d8082cf23 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -247,6 +247,7 @@
  *  - add FUSE_ATTR_EXCLUSIVE to enable exclusive mode for specific inodes
  *  - add FUSE_ATTR_IOMAP to enable iomap for specific inodes
  *  - add FUSE_IOMAP_CONFIG so the fuse server can configure more fs geometry
+ *  - add FUSE_NOTIFY_IOMAP_DEV_INVAL to invalidate iomap bdev ranges
  */
 
 #ifndef _LINUX_FUSE_H
@@ -701,6 +702,7 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_RESEND = 7,
 	FUSE_NOTIFY_INC_EPOCH = 8,
 	FUSE_NOTIFY_PRUNE = 9,
+	FUSE_NOTIFY_IOMAP_DEV_INVAL = 99,
 };
 
 /* The read buffer is required to be at least 8k, but may be much larger */
@@ -1421,4 +1423,17 @@ struct fuse_iomap_config_out {
 	int64_t s_maxbytes;	/* max file size */
 };
 
+struct fuse_range {
+	uint64_t offset;
+	uint64_t length;
+};
+
+struct fuse_iomap_dev_inval_out {
+	uint32_t dev;		/* device cookie */
+	uint32_t reserved;	/* zero */
+
+	/* range of bdev pagecache to invalidate, in bytes */
+	struct fuse_range range;
+};
+
 #endif /* _LINUX_FUSE_H */
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index a00b6d5a7fa0b6..95429ac096a82c 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -2208,6 +2208,21 @@ int fuse_lowlevel_iomap_device_add(struct fuse_session *se, int fd,
  */
 int fuse_lowlevel_iomap_device_remove(struct fuse_session *se, int device_id);
 
+/*
+ * Invalidate the page cache of a block device opened for use with iomap.
+ *
+ * Added in FUSE protocol version 7.99. If the kernel does not support
+ * this (or a newer) version, the function will return -ENOSYS and do
+ * nothing.
+ *
+ * @param se the session object
+ * @param dev device cookie returned by fuse_lowlevel_iomap_add_device
+ * @param offset start of the range to invalidate, in bytes
+ * @return length length of the range to invalidate, in bytes
+ */
+int fuse_lowlevel_iomap_device_invalidate(struct fuse_session *se, int dev,
+					  off_t offset, off_t length);
+
 /* ----------------------------------------------------------- *
  * Utility functions					       *
  * ----------------------------------------------------------- */
diff --git a/lib/fuse_lowlevel.c b/lib/fuse_lowlevel.c
index 19f292c0cb8ee3..89e26f207addbf 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -3684,6 +3684,28 @@ int fuse_lowlevel_notify_store(struct fuse_session *se, fuse_ino_t ino,
 	return res;
 }
 
+int fuse_lowlevel_iomap_device_invalidate(struct fuse_session *se, int dev,
+					  off_t offset, off_t length)
+{
+	struct fuse_iomap_dev_inval_out arg = {
+		.dev = dev,
+		.range.offset = offset,
+		.range.length = length,
+	};
+	struct iovec iov[2];
+
+	if (!se)
+		return -EINVAL;
+
+	if (!(se->conn.want_ext & FUSE_CAP_IOMAP))
+		return -ENOSYS;
+
+	iov[1].iov_base = &arg;
+	iov[1].iov_len = sizeof(arg);
+
+	return send_notify_iov(se, FUSE_NOTIFY_IOMAP_DEV_INVAL, iov, 2);
+}
+
 struct fuse_retrieve_req {
 	struct fuse_notify_req nreq;
 	void *cookie;
diff --git a/lib/fuse_versionscript b/lib/fuse_versionscript
index 14c59928ca9f00..56edd16862ca30 100644
--- a/lib/fuse_versionscript
+++ b/lib/fuse_versionscript
@@ -246,6 +246,7 @@ FUSE_3.99 {
 		fuse_fs_can_enable_iomapx;
 		fuse_lowlevel_discover_iomap;
 		fuse_reply_iomap_config;
+		fuse_lowlevel_iomap_device_invalidate;
 } FUSE_3.19;
 
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