linux-kernel - [PATCH v2 1/2] fuse: revalidate: move lookup into a separate function

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Message-ID: <e21fe75ba435ddc4d0b2e056c950dd421af794bf.1694541252.git.kjlx@templeofstupid.com>
Date:   Tue, 12 Sep 2023 11:34:22 -0700
From:   Krister Johansen <kjlx@...pleofstupid.com>
To:     Miklos Szeredi <miklos@...redi.hu>, linux-fsdevel@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org,
        German Maglione <gmaglione@...hat.com>,
        Greg Kurz <groug@...d.org>, Max Reitz <mreitz@...hat.com>,
        Bernd Schubert <bernd.schubert@...tmail.fm>
Subject: [PATCH v2 1/2] fuse: revalidate: move lookup into a separate function

If this refactoring seems cumbersome, it's because the goal is to move
the lookup parts of fuse_dentry_revalidate into a common function.  This
function will be used elsewhere in a separate commit.  In the meantime,
the new function fuse_dentry_revalidate_lookup is responsible for just
the lookup and validation portions of the revalidate dance.  The
fuse_dentry_revalidate function retains the responsibility for
invalidating and mutating any state associated with the origial
fuse_inode and dentry.

Cc: stable@...r.kernel.org
Fixes: 1866d779d5d2 ("fuse: Allow fuse_fill_super_common() for submounts")
Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
---
 fs/fuse/dir.c | 85 +++++++++++++++++++++++++++++++++++----------------
 1 file changed, 58 insertions(+), 27 deletions(-)

diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
index 04a1c62342dc..da5b6079d88c 100644
--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -183,6 +183,57 @@ static void fuse_lookup_init(struct fuse_conn *fc, struct fuse_args *args,
 	args->out_args[0].value = outarg;
 }
 
+static int fuse_dentry_revalidate_lookup(struct fuse_mount *fm,
+					 struct dentry *entry,
+					 struct inode *inode,
+					 struct fuse_entry_out *outarg,
+					 bool *lookedup)
+{
+	struct dentry *parent;
+	struct fuse_forget_link *forget;
+	FUSE_ARGS(args);
+	int ret;
+
+	forget = fuse_alloc_forget();
+	ret = -ENOMEM;
+	if (!forget)
+		goto out;
+
+	parent = dget_parent(entry);
+	fuse_lookup_init(fm->fc, &args, get_node_id(d_inode(parent)),
+			 &entry->d_name, outarg);
+	ret = fuse_simple_request(fm, &args);
+	dput(parent);
+
+	/* Zero nodeid is same as -ENOENT */
+	if (!ret && !outarg->nodeid)
+		ret = -ENOENT;
+	if (!ret) {
+		if (outarg->nodeid != get_node_id(inode) ||
+		    (bool) IS_AUTOMOUNT(inode) != (bool) (outarg->attr.flags & FUSE_ATTR_SUBMOUNT)) {
+			fuse_queue_forget(fm->fc, forget,
+					  outarg->nodeid, 1);
+			goto invalid;
+		}
+		*lookedup = true;
+	}
+	kfree(forget);
+	if (ret == -ENOMEM || ret == -EINTR)
+		goto out;
+	if (ret || fuse_invalid_attr(&outarg->attr) ||
+	    fuse_stale_inode(inode, outarg->generation, &outarg->attr)) {
+		goto invalid;
+	}
+
+	ret = 1;
+out:
+	return ret;
+
+invalid:
+	ret = 0;
+	goto out;
+}
+
 /*
  * Check whether the dentry is still valid
  *
@@ -206,9 +257,8 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 	else if (time_before64(fuse_dentry_time(entry), get_jiffies_64()) ||
 		 (flags & (LOOKUP_EXCL | LOOKUP_REVAL | LOOKUP_RENAME_TARGET))) {
 		struct fuse_entry_out outarg;
-		FUSE_ARGS(args);
-		struct fuse_forget_link *forget;
 		u64 attr_version;
+		bool lookedup = false;
 
 		/* For negative dentries, always do a fresh lookup */
 		if (!inode)
@@ -220,38 +270,19 @@ static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 
 		fm = get_fuse_mount(inode);
 
-		forget = fuse_alloc_forget();
-		ret = -ENOMEM;
-		if (!forget)
-			goto out;
-
 		attr_version = fuse_get_attr_version(fm->fc);
 
-		parent = dget_parent(entry);
-		fuse_lookup_init(fm->fc, &args, get_node_id(d_inode(parent)),
-				 &entry->d_name, &outarg);
-		ret = fuse_simple_request(fm, &args);
-		dput(parent);
-		/* Zero nodeid is same as -ENOENT */
-		if (!ret && !outarg.nodeid)
-			ret = -ENOENT;
-		if (!ret) {
+		ret = fuse_dentry_revalidate_lookup(fm, entry, inode, &outarg,
+						    &lookedup);
+		if (ret == -ENOMEM || ret == -EINTR)
+			goto out;
+		if (lookedup) {
 			fi = get_fuse_inode(inode);
-			if (outarg.nodeid != get_node_id(inode) ||
-			    (bool) IS_AUTOMOUNT(inode) != (bool) (outarg.attr.flags & FUSE_ATTR_SUBMOUNT)) {
-				fuse_queue_forget(fm->fc, forget,
-						  outarg.nodeid, 1);
-				goto invalid;
-			}
 			spin_lock(&fi->lock);
 			fi->nlookup++;
 			spin_unlock(&fi->lock);
 		}
-		kfree(forget);
-		if (ret == -ENOMEM || ret == -EINTR)
-			goto out;
-		if (ret || fuse_invalid_attr(&outarg.attr) ||
-		    fuse_stale_inode(inode, outarg.generation, &outarg.attr))
+		if (ret <= 0)
 			goto invalid;
 
 		forget_all_cached_acls(inode);
-- 
2.25.1