nilfs2: fix lockdep warnings during disk space reclamation

During disk space reclamation, nilfs2 still emits the following lockdep
warning due to page/folio operations on shadowed page caches that nilfs2
uses to get a snapshot of DAT file in memory:

  WARNING: CPU: 0 PID: 2643 at include/linux/backing-dev.h:272 __folio_mark_dirty+0x645/0x670
  ...
  RIP: 0010:__folio_mark_dirty+0x645/0x670
  ...
  Call Trace:
    filemap_dirty_folio+0x74/0xd0
    __set_page_dirty_nobuffers+0x85/0xb0
    nilfs_copy_dirty_pages+0x288/0x510 [nilfs2]
    nilfs_mdt_save_to_shadow_map+0x50/0xe0 [nilfs2]
    nilfs_clean_segments+0xee/0x5d0 [nilfs2]
    nilfs_ioctl_clean_segments.isra.19+0xb08/0xf40 [nilfs2]
    nilfs_ioctl+0xc52/0xfb0 [nilfs2]
    __x64_sys_ioctl+0x11d/0x170

This fixes the remaining warning by using inode objects to hold those
page caches.

Link: https://lkml.kernel.org/r/1647867427-30498-3-git-send-email-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Tested-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hao Sun <sunhao.th@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 59 insertions, 4 deletions

diff --git a/fs/nilfs2/inode.c b/fs/nilfs2/inode.c
index 2557f5f5a935..6045cea21f52 100644
--- a/fs/nilfs2/inode.c
+++ b/fs/nilfs2/inode.c
@@ -30,6 +30,7 @@
  * @root: pointer on NILFS root object (mounted checkpoint)
  * @for_gc: inode for GC flag
  * @for_btnc: inode for B-tree node cache flag
+ * @for_shadow: inode for shadowed page cache flag
  */
 struct nilfs_iget_args {
 	u64 ino;
@@ -37,6 +38,7 @@ struct nilfs_iget_args {
 	struct nilfs_root *root;
 	bool for_gc;
 	bool for_btnc;
+	bool for_shadow;
 };
 
 static int nilfs_iget_test(struct inode *inode, void *opaque);
@@ -315,7 +317,7 @@ static int nilfs_insert_inode_locked(struct inode *inode,
 {
 	struct nilfs_iget_args args = {
 		.ino = ino, .root = root, .cno = 0, .for_gc = false,
-		.for_btnc = false
+		.for_btnc = false, .for_shadow = false
 	};
 
 	return insert_inode_locked4(inode, ino, nilfs_iget_test, &args);
@@ -534,6 +536,12 @@ static int nilfs_iget_test(struct inode *inode, void *opaque)
 	} else if (args->for_btnc) {
 		return 0;
 	}
+	if (test_bit(NILFS_I_SHADOW, &ii->i_state)) {
+		if (!args->for_shadow)
+			return 0;
+	} else if (args->for_shadow) {
+		return 0;
+	}
 
 	if (!test_bit(NILFS_I_GCINODE, &ii->i_state))
 		return !args->for_gc;
@@ -555,6 +563,8 @@ static int nilfs_iget_set(struct inode *inode, void *opaque)
 		NILFS_I(inode)->i_state = BIT(NILFS_I_GCINODE);
 	if (args->for_btnc)
 		NILFS_I(inode)->i_state |= BIT(NILFS_I_BTNC);
+	if (args->for_shadow)
+		NILFS_I(inode)->i_state |= BIT(NILFS_I_SHADOW);
 	return 0;
 }
 
@@ -563,7 +573,7 @@ struct inode *nilfs_ilookup(struct super_block *sb, struct nilfs_root *root,
 {
 	struct nilfs_iget_args args = {
 		.ino = ino, .root = root, .cno = 0, .for_gc = false,
-		.for_btnc = false
+		.for_btnc = false, .for_shadow = false
 	};
 
 	return ilookup5(sb, ino, nilfs_iget_test, &args);
@@ -574,7 +584,7 @@ struct inode *nilfs_iget_locked(struct super_block *sb, struct nilfs_root *root,
 {
 	struct nilfs_iget_args args = {
 		.ino = ino, .root = root, .cno = 0, .for_gc = false,
-		.for_btnc = false
+		.for_btnc = false, .for_shadow = false
 	};
 
 	return iget5_locked(sb, ino, nilfs_iget_test, nilfs_iget_set, &args);
@@ -606,7 +616,7 @@ struct inode *nilfs_iget_for_gc(struct super_block *sb, unsigned long ino,
 {
 	struct nilfs_iget_args args = {
 		.ino = ino, .root = NULL, .cno = cno, .for_gc = true,
-		.for_btnc = false
+		.for_btnc = false, .for_shadow = false
 	};
 	struct inode *inode;
 	int err;
@@ -653,6 +663,7 @@ int nilfs_attach_btree_node_cache(struct inode *inode)
 	args.cno = ii->i_cno;
 	args.for_gc = test_bit(NILFS_I_GCINODE, &ii->i_state) != 0;
 	args.for_btnc = true;
+	args.for_shadow = test_bit(NILFS_I_SHADOW, &ii->i_state) != 0;
 
 	btnc_inode = iget5_locked(inode->i_sb, inode->i_ino, nilfs_iget_test,
 				  nilfs_iget_set, &args);
@@ -688,6 +699,50 @@ void nilfs_detach_btree_node_cache(struct inode *inode)
 	}
 }
 
+/**
+ * nilfs_iget_for_shadow - obtain inode for shadow mapping
+ * @inode: inode object that uses shadow mapping
+ *
+ * nilfs_iget_for_shadow() allocates a pair of inodes that holds page
+ * caches for shadow mapping.  The page cache for data pages is set up
+ * in one inode and the one for b-tree node pages is set up in the
+ * other inode, which is attached to the former inode.
+ *
+ * Return Value: On success, a pointer to the inode for data pages is
+ * returned. On errors, one of the following negative error code is returned
+ * in a pointer type.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ */
+struct inode *nilfs_iget_for_shadow(struct inode *inode)
+{
+	struct nilfs_iget_args args = {
+		.ino = inode->i_ino, .root = NULL, .cno = 0, .for_gc = false,
+		.for_btnc = false, .for_shadow = true
+	};
+	struct inode *s_inode;
+	int err;
+
+	s_inode = iget5_locked(inode->i_sb, inode->i_ino, nilfs_iget_test,
+			       nilfs_iget_set, &args);
+	if (unlikely(!s_inode))
+		return ERR_PTR(-ENOMEM);
+	if (!(s_inode->i_state & I_NEW))
+		return inode;
+
+	NILFS_I(s_inode)->i_flags = 0;
+	memset(NILFS_I(s_inode)->i_bmap, 0, sizeof(struct nilfs_bmap));
+	mapping_set_gfp_mask(s_inode->i_mapping, GFP_NOFS);
+
+	err = nilfs_attach_btree_node_cache(s_inode);
+	if (unlikely(err)) {
+		iget_failed(s_inode);
+		return ERR_PTR(err);
+	}
+	unlock_new_inode(s_inode);
+	return s_inode;
+}
+
 void nilfs_write_inode_common(struct inode *inode,
 			      struct nilfs_inode *raw_inode, int has_bmap)
 {