btrfs: remove inode number cache feature

It's been deprecated since commit b547a88e ("btrfs: start
deprecation of mount option inode_cache") which enumerates the reasons.

A filesystem that uses the feature (mount -o inode_cache) tracks the
inode numbers in bitmaps, that data stay on the filesystem after this
patch. The size is roughly 5MiB for 1M inodes [1], which is considered
small enough to be left there. Removal of the change can be implemented
in btrfs-progs if needed.

[1] https://lore.kernel.org/linux-btrfs/20201127145836.GZ6430@twin.jikos.cz/Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/Makefile

@@ -3,7 +3,7 @@
 obj-$(CONFIG_BTRFS_FS) := btrfs.o
 
 btrfs-y += super.o ctree.o extent-tree.o print-tree.o root-tree.o dir-item.o \
-	   file-item.o inode-item.o inode-map.o disk-io.o \
+	   file-item.o inode-item.o disk-io.o \
 	   transaction.o inode.o file.o tree-defrag.o \
 	   extent_map.o sysfs.o struct-funcs.o xattr.o ordered-data.o \
 	   extent_io.o volumes.o async-thread.o ioctl.o locking.o orphan.o \

fs/btrfs/ctree.h

@@ -1077,15 +1077,6 @@ struct btrfs_root {
 	spinlock_t accounting_lock;
 	struct btrfs_block_rsv *block_rsv;
 
-	/* free ino cache stuff */
-	struct btrfs_free_space_ctl *free_ino_ctl;
-	enum btrfs_caching_type ino_cache_state;
-	spinlock_t ino_cache_lock;
-	wait_queue_head_t ino_cache_wait;
-	struct btrfs_free_space_ctl *free_ino_pinned;
-	u64 ino_cache_progress;
-	struct inode *ino_cache_inode;
-
 	struct mutex log_mutex;
 	wait_queue_head_t log_writer_wait;
 	wait_queue_head_t log_commit_wait[2];
@@ -1359,7 +1350,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_USER_SUBVOL_RM_ALLOWED (1 << 14)
 #define BTRFS_MOUNT_ENOSPC_DEBUG	 (1 << 15)
 #define BTRFS_MOUNT_AUTO_DEFRAG		(1 << 16)
-#define BTRFS_MOUNT_INODE_MAP_CACHE	(1 << 17)
+/* bit 17 is free */
 #define BTRFS_MOUNT_USEBACKUPROOT	(1 << 18)
 #define BTRFS_MOUNT_SKIP_BALANCE	(1 << 19)
 #define BTRFS_MOUNT_CHECK_INTEGRITY	(1 << 20)
@@ -1406,9 +1397,7 @@ do {									\
  * transaction commit)
  */
 
-#define BTRFS_PENDING_SET_INODE_MAP_CACHE	(0)
-#define BTRFS_PENDING_CLEAR_INODE_MAP_CACHE	(1)
-#define BTRFS_PENDING_COMMIT			(2)
+#define BTRFS_PENDING_COMMIT			(0)
 
 #define btrfs_test_pending(info, opt)	\
 	test_bit(BTRFS_PENDING_##opt, &(info)->pending_changes)

fs/btrfs/disk-io.c

@@ -29,7 +29,6 @@
 #include "tree-log.h"
 #include "free-space-cache.h"
 #include "free-space-tree.h"
-#include "inode-map.h"
 #include "check-integrity.h"
 #include "rcu-string.h"
 #include "dev-replace.h"
@@ -1336,14 +1335,6 @@ static int btrfs_init_fs_root(struct btrfs_root *root, dev_t anon_dev)
 	int ret;
 	unsigned int nofs_flag;
 
-	root->free_ino_ctl = kzalloc(sizeof(*root->free_ino_ctl), GFP_NOFS);
-	root->free_ino_pinned = kzalloc(sizeof(*root->free_ino_pinned),
-					GFP_NOFS);
-	if (!root->free_ino_pinned || !root->free_ino_ctl) {
-		ret = -ENOMEM;
-		goto fail;
-	}
-
 	/*
 	 * We might be called under a transaction (e.g. indirect backref
 	 * resolution) which could deadlock if it triggers memory reclaim
@@ -1360,10 +1351,6 @@ static int btrfs_init_fs_root(struct btrfs_root *root, dev_t anon_dev)
 		btrfs_check_and_init_root_item(&root->root_item);
 	}
 
-	btrfs_init_free_ino_ctl(root);
-	spin_lock_init(&root->ino_cache_lock);
-	init_waitqueue_head(&root->ino_cache_wait);
-
 	/*
 	 * Don't assign anonymous block device to roots that are not exposed to
 	 * userspace, the id pool is limited to 1M
@@ -2033,8 +2020,6 @@ void btrfs_put_root(struct btrfs_root *root)
 			free_anon_bdev(root->anon_dev);
 		btrfs_drew_lock_destroy(&root->snapshot_lock);
 		free_root_extent_buffers(root);
-		kfree(root->free_ino_ctl);
-		kfree(root->free_ino_pinned);
 #ifdef CONFIG_BTRFS_DEBUG
 		spin_lock(&root->fs_info->fs_roots_radix_lock);
 		list_del_init(&root->leak_list);
@@ -3988,14 +3973,6 @@ void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 		}
 	}
 
-	if (root->free_ino_pinned)
-		__btrfs_remove_free_space_cache(root->free_ino_pinned);
-	if (root->free_ino_ctl)
-		__btrfs_remove_free_space_cache(root->free_ino_ctl);
-	if (root->ino_cache_inode) {
-		iput(root->ino_cache_inode);
-		root->ino_cache_inode = NULL;
-	}
 	if (drop_ref)
 		btrfs_put_root(root);
 }

fs/btrfs/free-space-cache.c

@@ -16,7 +16,6 @@
 #include "transaction.h"
 #include "disk-io.h"
 #include "extent_io.h"
-#include "inode-map.h"
 #include "volumes.h"
 #include "space-info.h"
 #include "delalloc-space.h"
@@ -37,10 +36,6 @@ static int link_free_space(struct btrfs_free_space_ctl *ctl,
 			   struct btrfs_free_space *info);
 static void unlink_free_space(struct btrfs_free_space_ctl *ctl,
 			      struct btrfs_free_space *info);
-static int btrfs_wait_cache_io_root(struct btrfs_root *root,
-			     struct btrfs_trans_handle *trans,
-			     struct btrfs_io_ctl *io_ctl,
-			     struct btrfs_path *path);
 static int search_bitmap(struct btrfs_free_space_ctl *ctl,
 			 struct btrfs_free_space *bitmap_info, u64 *offset,
 			 u64 *bytes, bool for_alloc);
@@ -1222,14 +1217,6 @@ static int __btrfs_wait_cache_io(struct btrfs_root *root,
 
 }
 
-static int btrfs_wait_cache_io_root(struct btrfs_root *root,
-				    struct btrfs_trans_handle *trans,
-				    struct btrfs_io_ctl *io_ctl,
-				    struct btrfs_path *path)
-{
-	return __btrfs_wait_cache_io(root, trans, NULL, io_ctl, path, 0);
-}
-
 int btrfs_wait_cache_io(struct btrfs_trans_handle *trans,
 			struct btrfs_block_group *block_group,
 			struct btrfs_path *path)
@@ -3807,170 +3794,6 @@ int btrfs_trim_block_group_bitmaps(struct btrfs_block_group *block_group,
 	return ret;
 }
 
-/*
- * Find the left-most item in the cache tree, and then return the
- * smallest inode number in the item.
- *
- * Note: the returned inode number may not be the smallest one in
- * the tree, if the left-most item is a bitmap.
- */
-u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root)
-{
-	struct btrfs_free_space_ctl *ctl = fs_root->free_ino_ctl;
-	struct btrfs_free_space *entry = NULL;
-	u64 ino = 0;
-
-	spin_lock(&ctl->tree_lock);
-
-	if (RB_EMPTY_ROOT(&ctl->free_space_offset))
-		goto out;
-
-	entry = rb_entry(rb_first(&ctl->free_space_offset),
-			 struct btrfs_free_space, offset_index);
-
-	if (!entry->bitmap) {
-		ino = entry->offset;
-
-		unlink_free_space(ctl, entry);
-		entry->offset++;
-		entry->bytes--;
-		if (!entry->bytes)
-			kmem_cache_free(btrfs_free_space_cachep, entry);
-		else
-			link_free_space(ctl, entry);
-	} else {
-		u64 offset = 0;
-		u64 count = 1;
-		int ret;
-
-		ret = search_bitmap(ctl, entry, &offset, &count, true);
-		/* Logic error; Should be empty if it can't find anything */
-		ASSERT(!ret);
-
-		ino = offset;
-		bitmap_clear_bits(ctl, entry, offset, 1);
-		if (entry->bytes == 0)
-			free_bitmap(ctl, entry);
-	}
-out:
-	spin_unlock(&ctl->tree_lock);
-
-	return ino;
-}
-
-struct inode *lookup_free_ino_inode(struct btrfs_root *root,
-				    struct btrfs_path *path)
-{
-	struct inode *inode = NULL;
-
-	spin_lock(&root->ino_cache_lock);
-	if (root->ino_cache_inode)
-		inode = igrab(root->ino_cache_inode);
-	spin_unlock(&root->ino_cache_lock);
-	if (inode)
-		return inode;
-
-	inode = __lookup_free_space_inode(root, path, 0);
-	if (IS_ERR(inode))
-		return inode;
-
-	spin_lock(&root->ino_cache_lock);
-	if (!btrfs_fs_closing(root->fs_info))
-		root->ino_cache_inode = igrab(inode);
-	spin_unlock(&root->ino_cache_lock);
-
-	return inode;
-}
-
-int create_free_ino_inode(struct btrfs_root *root,
-			  struct btrfs_trans_handle *trans,
-			  struct btrfs_path *path)
-{
-	return __create_free_space_inode(root, trans, path,
-					 BTRFS_FREE_INO_OBJECTID, 0);
-}
-
-int load_free_ino_cache(struct btrfs_fs_info *fs_info, struct btrfs_root *root)
-{
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct btrfs_path *path;
-	struct inode *inode;
-	int ret = 0;
-	u64 root_gen = btrfs_root_generation(&root->root_item);
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return 0;
-
-	/*
-	 * If we're unmounting then just return, since this does a search on the
-	 * normal root and not the commit root and we could deadlock.
-	 */
-	if (btrfs_fs_closing(fs_info))
-		return 0;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return 0;
-
-	inode = lookup_free_ino_inode(root, path);
-	if (IS_ERR(inode))
-		goto out;
-
-	if (root_gen != BTRFS_I(inode)->generation)
-		goto out_put;
-
-	ret = __load_free_space_cache(root, inode, ctl, path, 0);
-
-	if (ret < 0)
-		btrfs_err(fs_info,
-			"failed to load free ino cache for root %llu",
-			root->root_key.objectid);
-out_put:
-	iput(inode);
-out:
-	btrfs_free_path(path);
-	return ret;
-}
-
-int btrfs_write_out_ino_cache(struct btrfs_root *root,
-			      struct btrfs_trans_handle *trans,
-			      struct btrfs_path *path,
-			      struct inode *inode)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	int ret;
-	struct btrfs_io_ctl io_ctl;
-	bool release_metadata = true;
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return 0;
-
-	memset(&io_ctl, 0, sizeof(io_ctl));
-	ret = __btrfs_write_out_cache(root, inode, ctl, NULL, &io_ctl, trans);
-	if (!ret) {
-		/*
-		 * At this point writepages() didn't error out, so our metadata
-		 * reservation is released when the writeback finishes, at
-		 * inode.c:btrfs_finish_ordered_io(), regardless of it finishing
-		 * with or without an error.
-		 */
-		release_metadata = false;
-		ret = btrfs_wait_cache_io_root(root, trans, &io_ctl, path);
-	}
-
-	if (ret) {
-		if (release_metadata)
-			btrfs_delalloc_release_metadata(BTRFS_I(inode),
-					inode->i_size, true);
-		btrfs_debug(fs_info,
-			  "failed to write free ino cache for root %llu error %d",
-			  root->root_key.objectid, ret);
-	}
-
-	return ret;
-}
-
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 /*
  * Use this if you need to make a bitmap or extent entry specifically, it

fs/btrfs/free-space-cache.h

@@ -97,17 +97,6 @@ int btrfs_wait_cache_io(struct btrfs_trans_handle *trans,
 int btrfs_write_out_cache(struct btrfs_trans_handle *trans,
 			  struct btrfs_block_group *block_group,
 			  struct btrfs_path *path);
-struct inode *lookup_free_ino_inode(struct btrfs_root *root,
-				    struct btrfs_path *path);
-int create_free_ino_inode(struct btrfs_root *root,
-			  struct btrfs_trans_handle *trans,
-			  struct btrfs_path *path);
-int load_free_ino_cache(struct btrfs_fs_info *fs_info,
-			struct btrfs_root *root);
-int btrfs_write_out_ino_cache(struct btrfs_root *root,
-			      struct btrfs_trans_handle *trans,
-			      struct btrfs_path *path,
-			      struct inode *inode);
 
 void btrfs_init_free_space_ctl(struct btrfs_block_group *block_group,
 			       struct btrfs_free_space_ctl *ctl);
@@ -127,7 +116,6 @@ bool btrfs_is_free_space_trimmed(struct btrfs_block_group *block_group);
 u64 btrfs_find_space_for_alloc(struct btrfs_block_group *block_group,
 			       u64 offset, u64 bytes, u64 empty_size,
 			       u64 *max_extent_size);
-u64 btrfs_find_ino_for_alloc(struct btrfs_root *fs_root);
 void btrfs_dump_free_space(struct btrfs_block_group *block_group,
 			   u64 bytes);
 int btrfs_find_space_cluster(struct btrfs_block_group *block_group,

fs/btrfs/inode-map.h

-/* SPDX-License-Identifier: GPL-2.0 */
-
-#ifndef BTRFS_INODE_MAP_H
-#define BTRFS_INODE_MAP_H
-
-void btrfs_init_free_ino_ctl(struct btrfs_root *root);
-void btrfs_unpin_free_ino(struct btrfs_root *root);
-void btrfs_return_ino(struct btrfs_root *root, u64 objectid);
-int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid);
-int btrfs_save_ino_cache(struct btrfs_root *root,
-			 struct btrfs_trans_handle *trans);
-
-#endif

fs/btrfs/inode.c

@@ -45,7 +45,6 @@
 #include "compression.h"
 #include "locking.h"
 #include "free-space-cache.h"
-#include "inode-map.h"
 #include "props.h"
 #include "qgroup.h"
 #include "delalloc-space.h"
@@ -4214,12 +4213,6 @@ int btrfs_delete_subvolume(struct inode *dir, struct dentry *dentry)
 		d_invalidate(dentry);
 		btrfs_prune_dentries(dest);
 		ASSERT(dest->send_in_progress == 0);
-
-		/* the last ref */
-		if (dest->ino_cache_inode) {
-			iput(dest->ino_cache_inode);
-			dest->ino_cache_inode = NULL;
-		}
 	}
 
 	return ret;
@@ -5295,10 +5288,6 @@ void btrfs_evict_inode(struct inode *inode)
 		btrfs_end_transaction(trans);
 	}
 
-	if (!(root == fs_info->tree_root ||
-	      root->root_key.objectid == BTRFS_TREE_RELOC_OBJECTID))
-		btrfs_return_ino(root, btrfs_ino(BTRFS_I(inode)));
-
 free_rsv:
 	btrfs_free_block_rsv(fs_info, rsv);
 no_delete:

fs/btrfs/ioctl.c

@@ -34,7 +34,6 @@
 #include "print-tree.h"
 #include "volumes.h"
 #include "locking.h"
-#include "inode-map.h"
 #include "backref.h"
 #include "rcu-string.h"
 #include "send.h"

fs/btrfs/relocation.c

@@ -18,7 +18,6 @@
 #include "btrfs_inode.h"
 #include "async-thread.h"
 #include "free-space-cache.h"
-#include "inode-map.h"
 #include "qgroup.h"
 #include "print-tree.h"
 #include "delalloc-space.h"

fs/btrfs/super.c

@@ -338,7 +338,6 @@ enum {
 	Opt_device,
 	Opt_fatal_errors,
 	Opt_flushoncommit, Opt_noflushoncommit,
-	Opt_inode_cache, Opt_noinode_cache,
 	Opt_max_inline,
 	Opt_barrier, Opt_nobarrier,
 	Opt_datacow, Opt_nodatacow,
@@ -371,6 +370,7 @@ enum {
 
 	/* Deprecated options */
 	Opt_recovery,
+	Opt_inode_cache, Opt_noinode_cache,
 
 	/* Debugging options */
 	Opt_check_integrity,
@@ -880,14 +880,9 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 			}
 			break;
 		case Opt_inode_cache:
-			btrfs_warn(info,
-	"the 'inode_cache' option is deprecated and will have no effect from 5.11");
-			btrfs_set_pending_and_info(info, INODE_MAP_CACHE,
-					   "enabling inode map caching");
-			break;
 		case Opt_noinode_cache:
-			btrfs_clear_pending_and_info(info, INODE_MAP_CACHE,
-					     "disabling inode map caching");
+			btrfs_warn(info,
+	"the 'inode_cache' option is deprecated and has no effect since 5.11");
 			break;
 		case Opt_clear_cache:
 			btrfs_set_and_info(info, CLEAR_CACHE,
@@ -1506,8 +1501,6 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",enospc_debug");
 	if (btrfs_test_opt(info, AUTO_DEFRAG))
 		seq_puts(seq, ",autodefrag");
-	if (btrfs_test_opt(info, INODE_MAP_CACHE))
-		seq_puts(seq, ",inode_cache");
 	if (btrfs_test_opt(info, SKIP_BALANCE))
 		seq_puts(seq, ",skip_balance");
 #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY

fs/btrfs/transaction.c

@@ -16,7 +16,6 @@
 #include "transaction.h"
 #include "locking.h"
 #include "tree-log.h"
-#include "inode-map.h"
 #include "volumes.h"
 #include "dev-replace.h"
 #include "qgroup.h"
@@ -163,8 +162,6 @@ static noinline void switch_commit_roots(struct btrfs_trans_handle *trans)
 		list_del_init(&root->dirty_list);
 		free_extent_buffer(root->commit_root);
 		root->commit_root = btrfs_root_node(root);
-		if (is_fstree(root->root_key.objectid))
-			btrfs_unpin_free_ino(root);
 		extent_io_tree_release(&root->dirty_log_pages);
 		btrfs_qgroup_clean_swapped_blocks(root);
 	}
@@ -1342,8 +1339,6 @@ static noinline int commit_fs_roots(struct btrfs_trans_handle *trans)
 			btrfs_free_log(trans, root);
 			btrfs_update_reloc_root(trans, root);
 
-			btrfs_save_ino_cache(root, trans);
-
 			/* see comments in should_cow_block() */
 			clear_bit(BTRFS_ROOT_FORCE_COW, &root->state);
 			smp_mb__after_atomic();
@@ -2436,10 +2431,6 @@ int btrfs_clean_one_deleted_snapshot(struct btrfs_root *root)
 	btrfs_debug(fs_info, "cleaner removing %llu", root->root_key.objectid);
 
 	btrfs_kill_all_delayed_nodes(root);
-	if (root->ino_cache_inode) {
-		iput(root->ino_cache_inode);
-		root->ino_cache_inode = NULL;
-	}
 
 	if (btrfs_header_backref_rev(root->node) <
 			BTRFS_MIXED_BACKREF_REV)
@@ -2460,16 +2451,6 @@ void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info)
 	if (!prev)
 		return;
 
-	bit = 1 << BTRFS_PENDING_SET_INODE_MAP_CACHE;
-	if (prev & bit)
-		btrfs_set_opt(fs_info->mount_opt, INODE_MAP_CACHE);
-	prev &= ~bit;
-
-	bit = 1 << BTRFS_PENDING_CLEAR_INODE_MAP_CACHE;
-	if (prev & bit)
-		btrfs_clear_opt(fs_info->mount_opt, INODE_MAP_CACHE);
-	prev &= ~bit;
-
 	bit = 1 << BTRFS_PENDING_COMMIT;
 	if (prev & bit)
 		btrfs_debug(fs_info, "pending commit done");

fs/btrfs/tree-log.c

@@ -17,7 +17,6 @@
 #include "backref.h"
 #include "compression.h"
 #include "qgroup.h"
-#include "inode-map.h"
 #include "block-group.h"
 #include "space-info.h"