linux-ext4 - [PATCH 16/22] libfuse: add low level code to invalidate iomap block device ranges

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Message-ID: <176169813822.1427432.5342542917237250086.stgit@frogsfrogsfrogs>
Date: Tue, 28 Oct 2025 18:03:28 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: djwong@...nel.org, bschubert@....com
Cc: linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
 bernd@...ernd.com, miklos@...redi.hu, joannelkoong@...il.com, neal@...pa.dev
Subject: [PATCH 16/22] libfuse: add low level code to invalidate iomap block
 device ranges

From: Darrick J. Wong <djwong@...nel.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@...nel.org>
---
 include/fuse_kernel.h   |    9 +++++++++
 include/fuse_lowlevel.h |   15 +++++++++++++++
 lib/fuse_lowlevel.c     |   22 ++++++++++++++++++++++
 lib/fuse_versionscript  |    1 +
 4 files changed, 47 insertions(+)


diff --git a/include/fuse_kernel.h b/include/fuse_kernel.h
index 77123c3d0323f7..d1143e0c122b9c 100644
--- a/include/fuse_kernel.h
+++ b/include/fuse_kernel.h
@@ -244,6 +244,7 @@
  *  - add FUSE_IOMAP and iomap_{begin,end,ioend} for regular file operations
  *  - 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
@@ -694,6 +695,7 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_DELETE = 6,
 	FUSE_NOTIFY_RESEND = 7,
 	FUSE_NOTIFY_INC_EPOCH = 8,
+	FUSE_NOTIFY_IOMAP_DEV_INVAL = 99,
 	FUSE_NOTIFY_CODE_MAX,
 };
 
@@ -1404,4 +1406,11 @@ struct fuse_iomap_config_out {
 	int64_t s_maxbytes;	/* max file size */
 };
 
+struct fuse_iomap_dev_inval {
+	uint32_t dev;		/* device cookie */
+	uint32_t reserved;	/* zero */
+
+	uint64_t offset;	/* range to invalidate pagecache, bytes */
+	uint64_t length;
+};
 #endif /* _LINUX_FUSE_H */
diff --git a/include/fuse_lowlevel.h b/include/fuse_lowlevel.h
index 20c0a1e38595e1..110f7f73edbb2a 100644
--- a/include/fuse_lowlevel.h
+++ b/include/fuse_lowlevel.h
@@ -2158,6 +2158,21 @@ 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 3c3aa7aec9f494..db202b59a2f0e6 100644
--- a/lib/fuse_lowlevel.c
+++ b/lib/fuse_lowlevel.c
@@ -3548,6 +3548,28 @@ 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 arg = {
+		.dev = dev,
+		.offset = offset,
+		.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 6e57e943a60e2d..d268471ae5bd38 100644
--- a/lib/fuse_versionscript
+++ b/lib/fuse_versionscript
@@ -234,6 +234,7 @@ FUSE_3.99 {
 		fuse_fs_can_enable_iomapx;
 		fuse_lowlevel_discover_iomap;
 		fuse_reply_iomap_config;
+		fuse_lowlevel_iomap_device_invalidate;
 } FUSE_3.18;
 
 # Local Variables: