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From:   Jeff Layton <jlayton@kernel.org>
To:     linux-fsdevel@vger.kernel.org
Cc:     linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org,
        linux-cifs@vger.kernel.org, chuck.lever@oracle.com,
        viro@zeniv.linux.org.uk, hch@lst.de
Subject: [PATCH 1/7] filelock: add a new locks_inode_context accessor function
Date:   Wed, 16 Nov 2022 10:17:20 -0500
Message-Id: <20221116151726.129217-2-jlayton@kernel.org>
In-Reply-To: <20221116151726.129217-1-jlayton@kernel.org>
References: <20221116151726.129217-1-jlayton@kernel.org>
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There are a number of places in the kernel that are accessing the
inode->i_flctx field without smp_load_acquire. This is required to
ensure that the caller doesn't see a partially-initialized structure.

Add a new accessor function for it to make this clear.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/locks.c         | 20 ++++++++++----------
 include/linux/fs.h | 14 ++++++++++++++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/fs/locks.c b/fs/locks.c
index 9ccf89b6c95d..07436328dd0a 100644
--- a/fs/locks.c
+++ b/fs/locks.c
@@ -175,7 +175,7 @@ locks_get_lock_context(struct inode *inode, int type)
 	struct file_lock_context *ctx;
 
 	/* paired with cmpxchg() below */
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (likely(ctx) || type == F_UNLCK)
 		goto out;
 
@@ -194,7 +194,7 @@ locks_get_lock_context(struct inode *inode, int type)
 	 */
 	if (cmpxchg(&inode->i_flctx, NULL, ctx)) {
 		kmem_cache_free(flctx_cache, ctx);
-		ctx = smp_load_acquire(&inode->i_flctx);
+		ctx = locks_inode_context(inode);
 	}
 out:
 	trace_locks_get_lock_context(inode, type, ctx);
@@ -891,7 +891,7 @@ posix_test_lock(struct file *filp, struct file_lock *fl)
 	void *owner;
 	void (*func)(void);
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (!ctx || list_empty_careful(&ctx->flc_posix)) {
 		fl->fl_type = F_UNLCK;
 		return;
@@ -1483,7 +1483,7 @@ int __break_lease(struct inode *inode, unsigned int mode, unsigned int type)
 	new_fl->fl_flags = type;
 
 	/* typically we will check that ctx is non-NULL before calling */
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (!ctx) {
 		WARN_ON_ONCE(1);
 		goto free_lock;
@@ -1588,7 +1588,7 @@ void lease_get_mtime(struct inode *inode, struct timespec64 *time)
 	struct file_lock_context *ctx;
 	struct file_lock *fl;
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (ctx && !list_empty_careful(&ctx->flc_lease)) {
 		spin_lock(&ctx->flc_lock);
 		fl = list_first_entry_or_null(&ctx->flc_lease,
@@ -1634,7 +1634,7 @@ int fcntl_getlease(struct file *filp)
 	int type = F_UNLCK;
 	LIST_HEAD(dispose);
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (ctx && !list_empty_careful(&ctx->flc_lease)) {
 		percpu_down_read(&file_rwsem);
 		spin_lock(&ctx->flc_lock);
@@ -1823,7 +1823,7 @@ static int generic_delete_lease(struct file *filp, void *owner)
 	struct file_lock_context *ctx;
 	LIST_HEAD(dispose);
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (!ctx) {
 		trace_generic_delete_lease(inode, NULL);
 		return error;
@@ -2563,7 +2563,7 @@ void locks_remove_posix(struct file *filp, fl_owner_t owner)
 	 * posix_lock_file().  Another process could be setting a lock on this
 	 * file at the same time, but we wouldn't remove that lock anyway.
 	 */
-	ctx =  smp_load_acquire(&inode->i_flctx);
+	ctx =  locks_inode_context(inode);
 	if (!ctx || list_empty(&ctx->flc_posix))
 		return;
 
@@ -2684,7 +2684,7 @@ bool vfs_inode_has_locks(struct inode *inode)
 	struct file_lock_context *ctx;
 	bool ret;
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (!ctx)
 		return false;
 
@@ -2865,7 +2865,7 @@ void show_fd_locks(struct seq_file *f,
 	struct file_lock_context *ctx;
 	int id = 0;
 
-	ctx = smp_load_acquire(&inode->i_flctx);
+	ctx = locks_inode_context(inode);
 	if (!ctx)
 		return;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d6cb42b7e91c..092673178e13 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1187,6 +1187,13 @@ extern void show_fd_locks(struct seq_file *f,
 			 struct file *filp, struct files_struct *files);
 extern bool locks_owner_has_blockers(struct file_lock_context *flctx,
 			fl_owner_t owner);
+
+static inline struct file_lock_context *
+locks_inode_context(const struct inode *inode)
+{
+	return smp_load_acquire(&inode->i_flctx);
+}
+
 #else /* !CONFIG_FILE_LOCKING */
 static inline int fcntl_getlk(struct file *file, unsigned int cmd,
 			      struct flock __user *user)
@@ -1327,6 +1334,13 @@ static inline bool locks_owner_has_blockers(struct file_lock_context *flctx,
 {
 	return false;
 }
+
+static inline struct file_lock_context *
+locks_inode_context(const struct inode *inode)
+{
+	return NULL;
+}
+
 #endif /* !CONFIG_FILE_LOCKING */
 
 static inline struct inode *file_inode(const struct file *f)
-- 
2.38.1