btrfs: remove inode number cache feature

It's been deprecated since commit b547a88ea577 ("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>

1 files changed, 0 insertions, 527 deletions

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
deleted file mode 100644
index 2bc342fc5d7e..000000000000
--- a/fs/btrfs/inode-map.c
+++ /dev/null
@@ -1,527 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * Copyright (C) 2007 Oracle.  All rights reserved.
- */
-
-#include <linux/kthread.h>
-#include <linux/pagemap.h>
-
-#include "ctree.h"
-#include "disk-io.h"
-#include "free-space-cache.h"
-#include "inode-map.h"
-#include "transaction.h"
-#include "delalloc-space.h"
-
-static void fail_caching_thread(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-
-	btrfs_warn(fs_info, "failed to start inode caching task");
-	btrfs_clear_pending_and_info(fs_info, INODE_MAP_CACHE,
-				     "disabling inode map caching");
-	spin_lock(&root->ino_cache_lock);
-	root->ino_cache_state = BTRFS_CACHE_ERROR;
-	spin_unlock(&root->ino_cache_lock);
-	wake_up(&root->ino_cache_wait);
-}
-
-static int caching_kthread(void *data)
-{
-	struct btrfs_root *root = data;
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct btrfs_key key;
-	struct btrfs_path *path;
-	struct extent_buffer *leaf;
-	u64 last = (u64)-1;
-	int slot;
-	int ret;
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return 0;
-
-	path = btrfs_alloc_path();
-	if (!path) {
-		fail_caching_thread(root);
-		return -ENOMEM;
-	}
-
-	/* Since the commit root is read-only, we can safely skip locking. */
-	path->skip_locking = 1;
-	path->search_commit_root = 1;
-	path->reada = READA_FORWARD;
-
-	key.objectid = BTRFS_FIRST_FREE_OBJECTID;
-	key.offset = 0;
-	key.type = BTRFS_INODE_ITEM_KEY;
-again:
-	/* need to make sure the commit_root doesn't disappear */
-	down_read(&fs_info->commit_root_sem);
-
-	ret = btrfs_search_slot(NULL, root, &key, path, 0, 0);
-	if (ret < 0)
-		goto out;
-
-	while (1) {
-		if (btrfs_fs_closing(fs_info))
-			goto out;
-
-		leaf = path->nodes[0];
-		slot = path->slots[0];
-		if (slot >= btrfs_header_nritems(leaf)) {
-			ret = btrfs_next_leaf(root, path);
-			if (ret < 0)
-				goto out;
-			else if (ret > 0)
-				break;
-
-			if (need_resched() ||
-			    btrfs_transaction_in_commit(fs_info)) {
-				leaf = path->nodes[0];
-
-				if (WARN_ON(btrfs_header_nritems(leaf) == 0))
-					break;
-
-				/*
-				 * Save the key so we can advances forward
-				 * in the next search.
-				 */
-				btrfs_item_key_to_cpu(leaf, &key, 0);
-				btrfs_release_path(path);
-				root->ino_cache_progress = last;
-				up_read(&fs_info->commit_root_sem);
-				schedule_timeout(1);
-				goto again;
-			} else
-				continue;
-		}
-
-		btrfs_item_key_to_cpu(leaf, &key, slot);
-
-		if (key.type != BTRFS_INODE_ITEM_KEY)
-			goto next;
-
-		if (key.objectid >= root->highest_objectid)
-			break;
-
-		if (last != (u64)-1 && last + 1 != key.objectid) {
-			__btrfs_add_free_space(fs_info, ctl, last + 1,
-					       key.objectid - last - 1, 0);
-			wake_up(&root->ino_cache_wait);
-		}
-
-		last = key.objectid;
-next:
-		path->slots[0]++;
-	}
-
-	if (last < root->highest_objectid - 1) {
-		__btrfs_add_free_space(fs_info, ctl, last + 1,
-				       root->highest_objectid - last - 1, 0);
-	}
-
-	spin_lock(&root->ino_cache_lock);
-	root->ino_cache_state = BTRFS_CACHE_FINISHED;
-	spin_unlock(&root->ino_cache_lock);
-
-	root->ino_cache_progress = (u64)-1;
-	btrfs_unpin_free_ino(root);
-out:
-	wake_up(&root->ino_cache_wait);
-	up_read(&fs_info->commit_root_sem);
-
-	btrfs_free_path(path);
-
-	return ret;
-}
-
-static void start_caching(struct btrfs_root *root)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct task_struct *tsk;
-	int ret;
-	u64 objectid;
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return;
-
-	spin_lock(&root->ino_cache_lock);
-	if (root->ino_cache_state != BTRFS_CACHE_NO) {
-		spin_unlock(&root->ino_cache_lock);
-		return;
-	}
-
-	root->ino_cache_state = BTRFS_CACHE_STARTED;
-	spin_unlock(&root->ino_cache_lock);
-
-	ret = load_free_ino_cache(fs_info, root);
-	if (ret == 1) {
-		spin_lock(&root->ino_cache_lock);
-		root->ino_cache_state = BTRFS_CACHE_FINISHED;
-		spin_unlock(&root->ino_cache_lock);
-		wake_up(&root->ino_cache_wait);
-		return;
-	}
-
-	/*
-	 * It can be quite time-consuming to fill the cache by searching
-	 * through the extent tree, and this can keep ino allocation path
-	 * waiting. Therefore at start we quickly find out the highest
-	 * inode number and we know we can use inode numbers which fall in
-	 * [highest_ino + 1, BTRFS_LAST_FREE_OBJECTID].
-	 */
-	ret = btrfs_find_free_objectid(root, &objectid);
-	if (!ret && objectid <= BTRFS_LAST_FREE_OBJECTID) {
-		__btrfs_add_free_space(fs_info, ctl, objectid,
-				       BTRFS_LAST_FREE_OBJECTID - objectid + 1,
-				       0);
-		wake_up(&root->ino_cache_wait);
-	}
-
-	tsk = kthread_run(caching_kthread, root, "btrfs-ino-cache-%llu",
-			  root->root_key.objectid);
-	if (IS_ERR(tsk))
-		fail_caching_thread(root);
-}
-
-int btrfs_find_free_ino(struct btrfs_root *root, u64 *objectid)
-{
-	if (!btrfs_test_opt(root->fs_info, INODE_MAP_CACHE))
-		return btrfs_find_free_objectid(root, objectid);
-
-again:
-	*objectid = btrfs_find_ino_for_alloc(root);
-
-	if (*objectid != 0)
-		return 0;
-
-	start_caching(root);
-
-	wait_event(root->ino_cache_wait,
-		   root->ino_cache_state == BTRFS_CACHE_FINISHED ||
-		   root->ino_cache_state == BTRFS_CACHE_ERROR ||
-		   root->free_ino_ctl->free_space > 0);
-
-	if (root->ino_cache_state == BTRFS_CACHE_FINISHED &&
-	    root->free_ino_ctl->free_space == 0)
-		return -ENOSPC;
-	else if (root->ino_cache_state == BTRFS_CACHE_ERROR)
-		return btrfs_find_free_objectid(root, objectid);
-	else
-		goto again;
-}
-
-void btrfs_return_ino(struct btrfs_root *root, u64 objectid)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return;
-again:
-	if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
-	} else {
-		down_write(&fs_info->commit_root_sem);
-		spin_lock(&root->ino_cache_lock);
-		if (root->ino_cache_state == BTRFS_CACHE_FINISHED) {
-			spin_unlock(&root->ino_cache_lock);
-			up_write(&fs_info->commit_root_sem);
-			goto again;
-		}
-		spin_unlock(&root->ino_cache_lock);
-
-		start_caching(root);
-
-		__btrfs_add_free_space(fs_info, pinned, objectid, 1, 0);
-
-		up_write(&fs_info->commit_root_sem);
-	}
-}
-
-/*
- * When a transaction is committed, we'll move those inode numbers which are
- * smaller than root->ino_cache_progress from pinned tree to free_ino tree, and
- * others will just be dropped, because the commit root we were searching has
- * changed.
- *
- * Must be called with root->fs_info->commit_root_sem held
- */
-void btrfs_unpin_free_ino(struct btrfs_root *root)
-{
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct rb_root *rbroot = &root->free_ino_pinned->free_space_offset;
-	spinlock_t *rbroot_lock = &root->free_ino_pinned->tree_lock;
-	struct btrfs_free_space *info;
-	struct rb_node *n;
-	u64 count;
-
-	if (!btrfs_test_opt(root->fs_info, INODE_MAP_CACHE))
-		return;
-
-	while (1) {
-		spin_lock(rbroot_lock);
-		n = rb_first(rbroot);
-		if (!n) {
-			spin_unlock(rbroot_lock);
-			break;
-		}
-
-		info = rb_entry(n, struct btrfs_free_space, offset_index);
-		BUG_ON(info->bitmap); /* Logic error */
-
-		if (info->offset > root->ino_cache_progress)
-			count = 0;
-		else
-			count = min(root->ino_cache_progress - info->offset + 1,
-				    info->bytes);
-
-		rb_erase(&info->offset_index, rbroot);
-		spin_unlock(rbroot_lock);
-		if (count)
-			__btrfs_add_free_space(root->fs_info, ctl,
-					       info->offset, count, 0);
-		kmem_cache_free(btrfs_free_space_cachep, info);
-	}
-}
-
-#define INIT_THRESHOLD	((SZ_32K / 2) / sizeof(struct btrfs_free_space))
-#define INODES_PER_BITMAP (PAGE_SIZE * 8)
-
-/*
- * The goal is to keep the memory used by the free_ino tree won't
- * exceed the memory if we use bitmaps only.
- */
-static void recalculate_thresholds(struct btrfs_free_space_ctl *ctl)
-{
-	struct btrfs_free_space *info;
-	struct rb_node *n;
-	int max_ino;
-	int max_bitmaps;
-
-	n = rb_last(&ctl->free_space_offset);
-	if (!n) {
-		ctl->extents_thresh = INIT_THRESHOLD;
-		return;
-	}
-	info = rb_entry(n, struct btrfs_free_space, offset_index);
-
-	/*
-	 * Find the maximum inode number in the filesystem. Note we
-	 * ignore the fact that this can be a bitmap, because we are
-	 * not doing precise calculation.
-	 */
-	max_ino = info->bytes - 1;
-
-	max_bitmaps = ALIGN(max_ino, INODES_PER_BITMAP) / INODES_PER_BITMAP;
-	if (max_bitmaps <= ctl->total_bitmaps) {
-		ctl->extents_thresh = 0;
-		return;
-	}
-
-	ctl->extents_thresh = (max_bitmaps - ctl->total_bitmaps) *
-				PAGE_SIZE / sizeof(*info);
-}
-
-/*
- * We don't fall back to bitmap, if we are below the extents threshold
- * or this chunk of inode numbers is a big one.
- */
-static bool use_bitmap(struct btrfs_free_space_ctl *ctl,
-		       struct btrfs_free_space *info)
-{
-	if (ctl->free_extents < ctl->extents_thresh ||
-	    info->bytes > INODES_PER_BITMAP / 10)
-		return false;
-
-	return true;
-}
-
-static const struct btrfs_free_space_op free_ino_op = {
-	.recalc_thresholds	= recalculate_thresholds,
-	.use_bitmap		= use_bitmap,
-};
-
-static void pinned_recalc_thresholds(struct btrfs_free_space_ctl *ctl)
-{
-}
-
-static bool pinned_use_bitmap(struct btrfs_free_space_ctl *ctl,
-			      struct btrfs_free_space *info)
-{
-	/*
-	 * We always use extents for two reasons:
-	 *
-	 * - The pinned tree is only used during the process of caching
-	 *   work.
-	 * - Make code simpler. See btrfs_unpin_free_ino().
-	 */
-	return false;
-}
-
-static const struct btrfs_free_space_op pinned_free_ino_op = {
-	.recalc_thresholds	= pinned_recalc_thresholds,
-	.use_bitmap		= pinned_use_bitmap,
-};
-
-void btrfs_init_free_ino_ctl(struct btrfs_root *root)
-{
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct btrfs_free_space_ctl *pinned = root->free_ino_pinned;
-
-	spin_lock_init(&ctl->tree_lock);
-	ctl->unit = 1;
-	ctl->start = 0;
-	ctl->private = NULL;
-	ctl->op = &free_ino_op;
-	INIT_LIST_HEAD(&ctl->trimming_ranges);
-	mutex_init(&ctl->cache_writeout_mutex);
-
-	/*
-	 * Initially we allow to use 16K of ram to cache chunks of
-	 * inode numbers before we resort to bitmaps. This is somewhat
-	 * arbitrary, but it will be adjusted in runtime.
-	 */
-	ctl->extents_thresh = INIT_THRESHOLD;
-
-	spin_lock_init(&pinned->tree_lock);
-	pinned->unit = 1;
-	pinned->start = 0;
-	pinned->private = NULL;
-	pinned->extents_thresh = 0;
-	pinned->op = &pinned_free_ino_op;
-}
-
-int btrfs_save_ino_cache(struct btrfs_root *root,
-			 struct btrfs_trans_handle *trans)
-{
-	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct btrfs_free_space_ctl *ctl = root->free_ino_ctl;
-	struct btrfs_path *path;
-	struct inode *inode;
-	struct btrfs_block_rsv *rsv;
-	struct extent_changeset *data_reserved = NULL;
-	u64 num_bytes;
-	u64 alloc_hint = 0;
-	int ret;
-	int prealloc;
-	bool retry = false;
-
-	/* only fs tree and subvol/snap needs ino cache */
-	if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID &&
-	    (root->root_key.objectid < BTRFS_FIRST_FREE_OBJECTID ||
-	     root->root_key.objectid > BTRFS_LAST_FREE_OBJECTID))
-		return 0;
-
-	/* Don't save inode cache if we are deleting this root */
-	if (btrfs_root_refs(&root->root_item) == 0)
-		return 0;
-
-	if (!btrfs_test_opt(fs_info, INODE_MAP_CACHE))
-		return 0;
-
-	path = btrfs_alloc_path();
-	if (!path)
-		return -ENOMEM;
-
-	rsv = trans->block_rsv;
-	trans->block_rsv = &fs_info->trans_block_rsv;
-
-	num_bytes = trans->bytes_reserved;
-	/*
-	 * 1 item for inode item insertion if need
-	 * 4 items for inode item update (in the worst case)
-	 * 1 items for slack space if we need do truncation
-	 * 1 item for free space object
-	 * 3 items for pre-allocation
-	 */
-	trans->bytes_reserved = btrfs_calc_insert_metadata_size(fs_info, 10);
-	ret = btrfs_block_rsv_add(root, trans->block_rsv,
-				  trans->bytes_reserved,
-				  BTRFS_RESERVE_NO_FLUSH);
-	if (ret)
-		goto out;
-	trace_btrfs_space_reservation(fs_info, "ino_cache", trans->transid,
-				      trans->bytes_reserved, 1);
-again:
-	inode = lookup_free_ino_inode(root, path);
-	if (IS_ERR(inode) && (PTR_ERR(inode) != -ENOENT || retry)) {
-		ret = PTR_ERR(inode);
-		goto out_release;
-	}
-
-	if (IS_ERR(inode)) {
-		BUG_ON(retry); /* Logic error */
-		retry = true;
-
-		ret = create_free_ino_inode(root, trans, path);
-		if (ret)
-			goto out_release;
-		goto again;
-	}
-
-	BTRFS_I(inode)->generation = 0;
-	ret = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	if (ret) {
-		btrfs_abort_transaction(trans, ret);
-		goto out_put;
-	}
-
-	if (i_size_read(inode) > 0) {
-		ret = btrfs_truncate_free_space_cache(trans, NULL, inode);
-		if (ret) {
-			if (ret != -ENOSPC)
-				btrfs_abort_transaction(trans, ret);
-			goto out_put;
-		}
-	}
-
-	spin_lock(&root->ino_cache_lock);
-	if (root->ino_cache_state != BTRFS_CACHE_FINISHED) {
-		ret = -1;
-		spin_unlock(&root->ino_cache_lock);
-		goto out_put;
-	}
-	spin_unlock(&root->ino_cache_lock);
-
-	spin_lock(&ctl->tree_lock);
-	prealloc = sizeof(struct btrfs_free_space) * ctl->free_extents;
-	prealloc = ALIGN(prealloc, PAGE_SIZE);
-	prealloc += ctl->total_bitmaps * PAGE_SIZE;
-	spin_unlock(&ctl->tree_lock);
-
-	/* Just to make sure we have enough space */
-	prealloc += 8 * PAGE_SIZE;
-
-	ret = btrfs_delalloc_reserve_space(BTRFS_I(inode), &data_reserved, 0,
-					   prealloc);
-	if (ret)
-		goto out_put;
-
-	ret = btrfs_prealloc_file_range_trans(inode, trans, 0, 0, prealloc,
-					      prealloc, prealloc, &alloc_hint);
-	if (ret) {
-		btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc);
-		btrfs_delalloc_release_metadata(BTRFS_I(inode), prealloc, true);
-		goto out_put;
-	}
-
-	ret = btrfs_write_out_ino_cache(root, trans, path, inode);
-	btrfs_delalloc_release_extents(BTRFS_I(inode), prealloc);
-out_put:
-	iput(inode);
-out_release:
-	trace_btrfs_space_reservation(fs_info, "ino_cache", trans->transid,
-				      trans->bytes_reserved, 0);
-	btrfs_block_rsv_release(fs_info, trans->block_rsv,
-				trans->bytes_reserved, NULL);
-out:
-	trans->block_rsv = rsv;
-	trans->bytes_reserved = num_bytes;
-
-	btrfs_free_path(path);
-	extent_changeset_free(data_reserved);
-	return ret;
-}