From: Jun Wu <quark@meta.com>
Date: Fri, 15 May 2026 00:14:12 +0000 (-0700)
Subject: fuse: invalidate readdir cache on epoch bump
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0fa8346099b5794b9909989e3f1cb617e9d8d3fa;p=thirdparty%2Fkernel%2Flinux.git

fuse: invalidate readdir cache on epoch bump

FUSE_NOTIFY_INC_EPOCH invalidates dentries, but does not invalidate cached
readdir results. A process with cwd inside a FUSE mount can therefore
observe stale readdir(".") output after an epoch bump.

Fix this by recording epoch in the readdir cache and checking it on reuse.

Minimal reproducer:

- mount a tiny FUSE fs with an empty root directory
- on opendir, enable fi->cache_readdir and fi->keep_cache
- chdir into the mount and call readdir(".") to populate readdir cache
- make the FUSE server report one file in the root directory
- send only FUSE_NOTIFY_INC_EPOCH
- call readdir(".") again; before this change it stays stale, after this
  change it sees the new file

Fixes: 2396356a945b ("fuse: add more control over cache invalidation behaviour")
Signed-off-by: Jun Wu <quark@meta.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Reviewed-by: Luis Henriques <luis@igalia.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---

diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h
index 6455617b74a0c..85f738c531225 100644
--- a/fs/fuse/fuse_i.h
+++ b/fs/fuse/fuse_i.h
@@ -190,6 +190,11 @@ struct fuse_inode {
 			 */
 			struct timespec64 mtime;
 
+			/**
+			 * @epoch: epoch of fc when cache was started
+			 */
+			int epoch;
+
 			/**
 			 * @iversion: iversion of directory when cache was
 			 * started
diff --git a/fs/fuse/notify.c b/fs/fuse/notify.c
index 7cd63502e124b..f93d6fa05bf72 100644
--- a/fs/fuse/notify.c
+++ b/fs/fuse/notify.c
@@ -348,9 +348,9 @@ static int fuse_notify_resend(struct fuse_conn *fc)
 }
 
 /*
- * Increments the fuse connection epoch.  This will result of dentries from
- * previous epochs to be invalidated.  Additionally, if inval_wq is set, a work
- * queue is scheduled to trigger the invalidation.
+ * Increments the fuse connection epoch.  This will cause dentries and
+ * readdir caches from previous epochs to be invalidated.  Additionally,
+ * if inval_wq is set, a work queue is scheduled to trigger the invalidation.
  */
 static int fuse_notify_inc_epoch(struct fuse_conn *fc)
 {
diff --git a/fs/fuse/readdir.c b/fs/fuse/readdir.c
index e993255584dfd..a94b00e13f6ee 100644
--- a/fs/fuse/readdir.c
+++ b/fs/fuse/readdir.c
@@ -489,6 +489,7 @@ static void fuse_rdc_reset(struct inode *inode)
 	fi->rdc.version++;
 	fi->rdc.size = 0;
 	fi->rdc.pos = 0;
+	fi->rdc.epoch = 0;
 }
 
 #define UNCACHED 1
@@ -530,6 +531,7 @@ retry_locked:
 		if (!ctx->pos && !fi->rdc.size) {
 			fi->rdc.mtime = inode_get_mtime(inode);
 			fi->rdc.iversion = inode_query_iversion(inode);
+			fi->rdc.epoch = atomic_read(&fc->epoch);
 		}
 		spin_unlock(&fi->rdc.lock);
 		return UNCACHED;
@@ -543,7 +545,8 @@ retry_locked:
 		struct timespec64 mtime = inode_get_mtime(inode);
 
 		if (inode_peek_iversion(inode) != fi->rdc.iversion ||
-		    !timespec64_equal(&fi->rdc.mtime, &mtime)) {
+		    !timespec64_equal(&fi->rdc.mtime, &mtime) ||
+		    fi->rdc.epoch != atomic_read(&fc->epoch)) {
 			fuse_rdc_reset(inode);
 			goto retry_locked;
 		}