linux-kernel - [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

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Message-ID: <20250210094840.5627-1-luis@igalia.com>
Date: Mon, 10 Feb 2025 09:48:40 +0000
From: Luis Henriques <luis@...lia.com>
To: Miklos Szeredi <miklos@...redi.hu>,
	Bernd Schubert <bschubert@....com>
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Luis Henriques <luis@...lia.com>
Subject: [RFC PATCH v2] fuse: add new function to invalidate cache for all inodes

Currently userspace is able to notify the kernel to invalidate the cache for
an inode.  This means that, if all the inodes in a filesystem need to be
invalidated, then userspace needs to iterate through all of them and do this
kernel notification separately.

This patch adds a new option that allows userspace to invalidate all the
inodes with a single notification operation.  In addition to invalidate all
the inodes, it also shrinks the sb dcache.

Signed-off-by: Luis Henriques <luis@...lia.com>
---
Hi!

As suggested by Bernd, this patch v2 simply adds an helper function that
will make it easier to replace most of it's code by a call to function
super_iter_inodes() when Dave Chinner's patch[1] eventually gets merged.

[1] https://lore.kernel.org/r/20241002014017.3801899-3-david@fromorbit.com

 fs/fuse/inode.c           | 59 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fuse.h |  3 ++
 2 files changed, 62 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index e9db2cb8c150..be51b53006d8 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -547,6 +547,62 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
 	return NULL;
 }
 
+static void inval_single_inode(struct inode *inode, struct fuse_conn *fc)
+{
+	struct fuse_inode *fi;
+
+	fi = get_fuse_inode(inode);
+	spin_lock(&fi->lock);
+	fi->attr_version = atomic64_inc_return(&fc->attr_version);
+	spin_unlock(&fi->lock);
+	fuse_invalidate_attr(inode);
+	forget_all_cached_acls(inode);
+}
+
+static int fuse_reverse_inval_all(struct fuse_conn *fc)
+{
+	struct fuse_mount *fm;
+	struct super_block *sb;
+	struct inode *inode, *old_inode = NULL;
+
+	inode = fuse_ilookup(fc, FUSE_ROOT_ID, NULL);
+	if (!inode)
+		return -ENOENT;
+
+	fm = get_fuse_mount(inode);
+	iput(inode);
+	if (!fm)
+		return -ENOENT;
+	sb = fm->sb;
+
+	spin_lock(&sb->s_inode_list_lock);
+	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
+		spin_lock(&inode->i_lock);
+		if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
+		    !atomic_read(&inode->i_count)) {
+			spin_unlock(&inode->i_lock);
+			continue;
+		}
+
+		__iget(inode);
+		spin_unlock(&inode->i_lock);
+		spin_unlock(&sb->s_inode_list_lock);
+		iput(old_inode);
+
+		inval_single_inode(inode, fc);
+
+		old_inode = inode;
+		cond_resched();
+		spin_lock(&sb->s_inode_list_lock);
+	}
+	spin_unlock(&sb->s_inode_list_lock);
+	iput(old_inode);
+
+	shrink_dcache_sb(sb);
+
+	return 0;
+}
+
 int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
 			     loff_t offset, loff_t len)
 {
@@ -555,6 +611,9 @@ int fuse_reverse_inval_inode(struct fuse_conn *fc, u64 nodeid,
 	pgoff_t pg_start;
 	pgoff_t pg_end;
 
+	if (nodeid == FUSE_INVAL_ALL_INODES)
+		return fuse_reverse_inval_all(fc);
+
 	inode = fuse_ilookup(fc, nodeid, NULL);
 	if (!inode)
 		return -ENOENT;
diff --git a/include/uapi/linux/fuse.h b/include/uapi/linux/fuse.h
index 5e0eb41d967e..e5852b63f99f 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -669,6 +669,9 @@ enum fuse_notify_code {
 	FUSE_NOTIFY_CODE_MAX,
 };
 
+/* The nodeid to request to invalidate all inodes */
+#define FUSE_INVAL_ALL_INODES 0
+
 /* The read buffer is required to be at least 8k, but may be much larger */
 #define FUSE_MIN_READ_BUFFER 8192