bcachefs: fix truncate with ATTR_MODE

After the v5.12 rebase, we started oopsing when truncate was passed
ATTR_MODE, due to not passing mnt_userns to setattr_copy(). This
refactors things so that truncate/extend finish by using
bch2_setattr_nonsize(), which solves the problem.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/fs-io.c

@@ -2252,11 +2252,11 @@ static int bch2_truncate_page(struct bch_inode_info *inode, loff_t from)
 				    from, round_up(from, PAGE_SIZE));
 }
 
-static int bch2_extend(struct bch_inode_info *inode,
+static int bch2_extend(struct mnt_idmap *idmap,
+		       struct bch_inode_info *inode,
 		       struct bch_inode_unpacked *inode_u,
 		       struct iattr *iattr)
 {
-	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct address_space *mapping = inode->v.i_mapping;
 	int ret;
 
@@ -2270,25 +2270,15 @@ static int bch2_extend(struct bch_inode_info *inode,
 		return ret;
 
 	truncate_setsize(&inode->v, iattr->ia_size);
-	/* ATTR_MODE will never be set here, ns argument isn't needed: */
-	setattr_copy(NULL, &inode->v, iattr);
-
-	mutex_lock(&inode->ei_update_lock);
-	ret = bch2_write_inode_size(c, inode, inode->v.i_size,
-				    ATTR_MTIME|ATTR_CTIME);
-	mutex_unlock(&inode->ei_update_lock);
 
-	return ret;
+	return bch2_setattr_nonsize(idmap, inode, iattr);
 }
 
 static int bch2_truncate_finish_fn(struct bch_inode_info *inode,
 				   struct bch_inode_unpacked *bi,
 				   void *p)
 {
-	struct bch_fs *c = inode->v.i_sb->s_fs_info;
-
 	bi->bi_flags &= ~BCH_INODE_I_SIZE_DIRTY;
-	bi->bi_mtime = bi->bi_ctime = bch2_current_time(c);
 	return 0;
 }
 
@@ -2302,7 +2292,8 @@ static int bch2_truncate_start_fn(struct bch_inode_info *inode,
 	return 0;
 }
 
-int bch2_truncate(struct bch_inode_info *inode, struct iattr *iattr)
+int bch2_truncate(struct mnt_idmap *idmap,
+		  struct bch_inode_info *inode, struct iattr *iattr)
 {
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct address_space *mapping = inode->v.i_mapping;
@@ -2313,6 +2304,18 @@ int bch2_truncate(struct bch_inode_info *inode, struct iattr *iattr)
 	s64 i_sectors_delta = 0;
 	int ret = 0;
 
+	/*
+	 * Don't update timestamps if we're not doing anything:
+	 */
+	if (iattr->ia_size == inode->v.i_size)
+		return 0;
+
+	if (!(iattr->ia_valid & ATTR_MTIME))
+		ktime_get_coarse_real_ts64(&iattr->ia_mtime);
+	if (!(iattr->ia_valid & ATTR_CTIME))
+		ktime_get_coarse_real_ts64(&iattr->ia_ctime);
+	iattr->ia_valid |= ATTR_MTIME|ATTR_CTIME;
+
 	inode_dio_wait(&inode->v);
 	bch2_pagecache_block_get(&inode->ei_pagecache_lock);
 
@@ -2342,10 +2345,12 @@ int bch2_truncate(struct bch_inode_info *inode, struct iattr *iattr)
 		inode->v.i_size < inode_u.bi_size);
 
 	if (iattr->ia_size > inode->v.i_size) {
-		ret = bch2_extend(inode, &inode_u, iattr);
+		ret = bch2_extend(idmap, inode, &inode_u, iattr);
 		goto err;
 	}
 
+	iattr->ia_valid &= ~ATTR_SIZE;
+
 	ret = bch2_truncate_page(inode, iattr->ia_size);
 	if (unlikely(ret))
 		goto err;
@@ -2389,13 +2394,11 @@ int bch2_truncate(struct bch_inode_info *inode, struct iattr *iattr)
 	if (unlikely(ret))
 		goto err;
 
-	/* ATTR_MODE will never be set here, ns argument isn't needed: */
-	setattr_copy(NULL, &inode->v, iattr);
-
 	mutex_lock(&inode->ei_update_lock);
-	ret = bch2_write_inode(c, inode, bch2_truncate_finish_fn, NULL,
-			       ATTR_MTIME|ATTR_CTIME);
+	ret = bch2_write_inode(c, inode, bch2_truncate_finish_fn, NULL, 0);
 	mutex_unlock(&inode->ei_update_lock);
+
+	ret = bch2_setattr_nonsize(idmap, inode, iattr);
 err:
 	bch2_pagecache_block_put(&inode->ei_pagecache_lock);
 	return ret;

fs/bcachefs/fs-io.h

@@ -31,7 +31,8 @@ ssize_t bch2_write_iter(struct kiocb *, struct iov_iter *);
 
 int bch2_fsync(struct file *, loff_t, loff_t, int);
 
-int bch2_truncate(struct bch_inode_info *, struct iattr *);
+int bch2_truncate(struct mnt_idmap *,
+		  struct bch_inode_info *, struct iattr *);
 long bch2_fallocate_dispatch(struct file *, int, loff_t, loff_t);
 
 loff_t bch2_remap_file_range(struct file *, loff_t, struct file *,

fs/bcachefs/fs.c

@@ -662,6 +662,9 @@ static void bch2_setattr_copy(struct mnt_idmap *idmap,
 	if (ia_valid & ATTR_GID)
 		bi->bi_gid = from_kgid(i_user_ns(&inode->v), attr->ia_gid);
 
+	if (ia_valid & ATTR_SIZE)
+		bi->bi_size = attr->ia_size;
+
 	if (ia_valid & ATTR_ATIME)
 		bi->bi_atime = timespec_to_bch2_time(c, attr->ia_atime);
 	if (ia_valid & ATTR_MTIME)
@@ -682,9 +685,9 @@ static void bch2_setattr_copy(struct mnt_idmap *idmap,
 	}
 }
 
-static int bch2_setattr_nonsize(struct mnt_idmap *idmap,
-				struct bch_inode_info *inode,
-				struct iattr *attr)
+int bch2_setattr_nonsize(struct mnt_idmap *idmap,
+			 struct bch_inode_info *inode,
+			 struct iattr *attr)
 {
 	struct bch_fs *c = inode->v.i_sb->s_fs_info;
 	struct bch_qid qid;
@@ -808,7 +811,7 @@ static int bch2_setattr(struct mnt_idmap *idmap,
 		return ret;
 
 	return iattr->ia_valid & ATTR_SIZE
-		? bch2_truncate(inode, iattr)
+		? bch2_truncate(idmap, inode, iattr)
 		: bch2_setattr_nonsize(idmap, inode, iattr);
 }
 

fs/bcachefs/fs.h

@@ -166,6 +166,10 @@ void bch2_inode_update_after_write(struct bch_fs *,
 int __must_check bch2_write_inode(struct bch_fs *, struct bch_inode_info *,
 				  inode_set_fn, void *, unsigned);
 
+int bch2_setattr_nonsize(struct mnt_idmap *,
+			 struct bch_inode_info *,
+			 struct iattr *);
+
 void bch2_vfs_exit(void);
 int bch2_vfs_init(void);