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

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Message-ID: <20250115163253.8402-1-luis@igalia.com>
Date: Wed, 15 Jan 2025 16:32:53 +0000
From: Luis Henriques <luis@...lia.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Matt Harvey <mharvey@...ptrading.com>,
	Luis Henriques <luis@...lia.com>
Subject: [RFC PATCH] 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 superblock dcache.

Signed-off-by: Luis Henriques <luis@...lia.com>
---
Just an additional note that this patch could eventually be simplified if
Dave Chinner patch to iterate through the superblock inodes[1] is merged.

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

 fs/fuse/inode.c           | 53 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/fuse.h |  3 +++
 2 files changed, 56 insertions(+)

diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c
index 3ce4f4e81d09..1fd9a5f303da 100644
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -546,6 +546,56 @@ struct inode *fuse_ilookup(struct fuse_conn *fc, u64 nodeid,
 	return NULL;
 }
 
+static int fuse_reverse_inval_all(struct fuse_conn *fc)
+{
+	struct fuse_mount *fm;
+	struct super_block *sb;
+	struct inode *inode, *old_inode = NULL;
+	struct fuse_inode *fi;
+
+	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);
+
+		fi = get_fuse_inode(inode);
+		spin_lock(&fi->lock);
+		fi->attr_version = atomic64_inc_return(&fm->fc->attr_version);
+		spin_unlock(&fi->lock);
+		fuse_invalidate_attr(inode);
+		forget_all_cached_acls(inode);
+
+		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)
 {
@@ -554,6 +604,9 @@ 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 f1e99458e29e..e9e78292d107 100644
--- a/include/uapi/linux/fuse.h
+++ b/include/uapi/linux/fuse.h
@@ -658,6 +658,9 @@ 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