fs: add might_sleep() annotation to iput() and more

When iput() drops the reference counter to zero, it may sleep via
inode_wait_for_writeback().  This happens rarely because it's usually
the dcache which evicts inodes, but really iput() should only ever be
called in contexts where sleeping is allowed.  This annotation allows
finding buggy callers.

Additionally, this patch annotates a few low-level functions that can
call iput() conditionally.

Cc: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Link: https://lore.kernel.org/20250917153632.2228828-1-max.kellermann@ionos.com
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: MaxKellermann

fs/inode.c

@@ -1279,6 +1279,8 @@ struct inode *inode_insert5(struct inode *inode, unsigned long hashval,
 	struct hlist_head *head = inode_hashtable + hash(inode->i_sb, hashval);
 	struct inode *old;
 
+	might_sleep();
+
 again:
 	spin_lock(&inode_hash_lock);
 	old = find_inode(inode->i_sb, head, test, data, true);
@@ -1382,6 +1384,8 @@ struct inode *iget5_locked_rcu(struct super_block *sb, unsigned long hashval,
 	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
 	struct inode *inode, *new;
 
+	might_sleep();
+
 again:
 	inode = find_inode(sb, head, test, data, false);
 	if (inode) {
@@ -1422,6 +1426,9 @@ struct inode *iget_locked(struct super_block *sb, unsigned long ino)
 {
 	struct hlist_head *head = inode_hashtable + hash(sb, ino);
 	struct inode *inode;
+
+	might_sleep();
+
 again:
 	inode = find_inode_fast(sb, head, ino, false);
 	if (inode) {
@@ -1605,6 +1612,9 @@ struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
 		int (*test)(struct inode *, void *), void *data)
 {
 	struct inode *inode;
+
+	might_sleep();
+
 again:
 	inode = ilookup5_nowait(sb, hashval, test, data);
 	if (inode) {
@@ -1630,6 +1640,9 @@ struct inode *ilookup(struct super_block *sb, unsigned long ino)
 {
 	struct hlist_head *head = inode_hashtable + hash(sb, ino);
 	struct inode *inode;
+
+	might_sleep();
+
 again:
 	inode = find_inode_fast(sb, head, ino, false);
 
@@ -1780,6 +1793,8 @@ int insert_inode_locked(struct inode *inode)
 	ino_t ino = inode->i_ino;
 	struct hlist_head *head = inode_hashtable + hash(sb, ino);
 
+	might_sleep();
+
 	while (1) {
 		struct inode *old = NULL;
 		spin_lock(&inode_hash_lock);
@@ -1826,6 +1841,8 @@ int insert_inode_locked4(struct inode *inode, unsigned long hashval,
 {
 	struct inode *old;
 
+	might_sleep();
+
 	inode->i_state |= I_CREATING;
 	old = inode_insert5(inode, hashval, test, NULL, data);
 
@@ -1908,6 +1925,7 @@ static void iput_final(struct inode *inode)
  */
 void iput(struct inode *inode)
 {
+	might_sleep();
 	if (unlikely(!inode))
 		return;