From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97B7C3E5A2C for ; Wed, 13 May 2026 08:54:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778662491; cv=none; b=WVyOWdU+g7kHV3R1jH4Xcc9l2sGWkM8komRakPWJ7+I1//08PuU6dASP57h31IhAC9s6umddDgg7IRaYDFlnBN8IDYBo+oWujrwi/Zxpb/s0TF/cEIkDV5tm+9aMWo5mEqEZ3b9/eOmbXy5Kq08GIxWAUI9+9vD9KiVDKElnLig= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778662491; c=relaxed/simple; bh=Puj1Ro9OI6zZxkMJIHy1KCRFn2WSYjIRU73PSWFBXNc=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=gHt5Tn3KJIz59GNOLhEVWEqiBSURx0LA8RMfTUpPPi2cRkEssy0Lk9MVUyfkAw2IpyLUBKR6fWeZbAZkIJHG63xM9LKCo+mGUo6zH2wNNTDDYhhr0V8bwUS5a1A5xfieyCCgM8/NOCJ83zlZM2MdSbW+dRBZjc0y7LfV198WrW4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com; spf=pass smtp.mailfrom=suse.com; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=suse.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.com Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 5EC5B5CE45; Wed, 13 May 2026 08:54:22 +0000 (UTC) Authentication-Results: smtp-out1.suse.de; none Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 3806C593A9; Wed, 13 May 2026 08:54:22 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id ePItDT48BGpERwAAD6G6ig (envelope-from ); Wed, 13 May 2026 08:54:22 +0000 From: Daniel Vacek To: Chris Mason , Josef Bacik , Eric Biggers , "Theodore Y. Ts'o" , Jaegeuk Kim , Jens Axboe , David Sterba Cc: linux-block@vger.kernel.org, Daniel Vacek , linux-fscrypt@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, Boris Burkov Subject: [PATCH v7 09/43] btrfs: add infrastructure for safe em freeing Date: Wed, 13 May 2026 10:52:43 +0200 Message-ID: <20260513085340.3673127-10-neelx@suse.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260513085340.3673127-1-neelx@suse.com> References: <20260513085340.3673127-1-neelx@suse.com> Precedence: bulk X-Mailing-List: linux-block@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[] X-Rspamd-Queue-Id: 5EC5B5CE45 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spam-Score: -4.00 X-Spam-Level: X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Flag: NO X-Rspamd-Action: no action From: Josef Bacik When we add fscrypt support we're going to have fscrypt objects hanging off of extent_maps. This includes a block key, which if we're the last one freeing the key we may have to unregister it from the block layer. This requires taking a semaphore in the block layer, which means we can't free em's under the extent map tree lock. Thankfully we only do this in two places, one where we're dropping a range of extent maps, and when we're freeing logged extents. Add a free_extent_map_safe() which will add the em to a list in the em_tree if we free'd the object. Currently this is unconditional but will be changed to conditional on the fscrypt object we will add in a later patch. To process these delayed objects add a free_pending_extent_maps() that is called after the lock has been dropped on the em_tree. This will process the extent maps on the freed list and do the appropriate freeing work in a safe manner. Signed-off-by: Josef Bacik Reviewed-by: Boris Burkov Signed-off-by: Daniel Vacek --- v5: https://lore.kernel.org/linux-btrfs/6cf44f7860e94de68df242e69f4c5250bd061cff.1706116485.git.josef@toxicpanda.com/ * No changes since (other than simple function renames). --- fs/btrfs/extent_map.c | 76 +++++++++++++++++++++++++++++++++++++++++-- fs/btrfs/extent_map.h | 10 ++++++ fs/btrfs/tree-log.c | 6 ++-- 3 files changed, 87 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c index 9284c0a81bef..61fe262667ee 100644 --- a/fs/btrfs/extent_map.c +++ b/fs/btrfs/extent_map.c @@ -34,7 +34,9 @@ void __cold btrfs_extent_map_exit(void) void btrfs_extent_map_tree_init(struct extent_map_tree *tree) { tree->root = RB_ROOT; + tree->flags = 0; INIT_LIST_HEAD(&tree->modified_extents); + INIT_LIST_HEAD(&tree->freed_extents); rwlock_init(&tree->lock); } @@ -51,9 +53,15 @@ struct extent_map *btrfs_alloc_extent_map(void) RB_CLEAR_NODE(&em->rb_node); refcount_set(&em->refs, 1); INIT_LIST_HEAD(&em->list); + INIT_LIST_HEAD(&em->free_list); return em; } +static void free_extent_map(struct extent_map *em) +{ + kmem_cache_free(extent_map_cache, em); +} + /* * Drop the reference out on @em by one and free the structure if the reference * count hits zero. @@ -65,10 +73,69 @@ void btrfs_free_extent_map(struct extent_map *em) if (refcount_dec_and_test(&em->refs)) { WARN_ON(btrfs_extent_map_in_tree(em)); WARN_ON(!list_empty(&em->list)); - kmem_cache_free(extent_map_cache, em); + free_extent_map(em); + } +} + +/* + * Drop a ref for the extent map in the given tree. + * + * @tree: tree that the em is a part of. + * @em: the em to drop the reference to. + * + * Drop the reference count on @em by one, if the reference count hits 0 and + * there is an object on the em that can't be safely freed in the current + * context (if we are holding the extent_map_tree->lock for example), then add + * it to the freed_extents list on the extent_map_tree for later processing. + * + * This must be followed by a btrfs_free_pending_extent_maps() to clear + * the pending frees. + */ +void btrfs_free_extent_map_safe(struct extent_map_tree *tree, + struct extent_map *em) +{ + lockdep_assert_held_write(&tree->lock); + + if (!em) + return; + + if (refcount_dec_and_test(&em->refs)) { + WARN_ON(btrfs_extent_map_in_tree(em)); + WARN_ON(!list_empty(&em->list)); + list_add_tail(&em->free_list, &tree->freed_extents); + set_bit(EXTENT_MAP_TREE_PENDING_FREES, &tree->flags); } } +/* + * Free the em objects that exist on the em tree + * + * @tree: the tree to free the objects from. + * + * If there are any objects on the em->freed_extents list go ahead and + * free them here in a safe way. This is to be coupled with any uses of + * btrfs_free_extent_map_safe(). + */ +void btrfs_free_pending_extent_maps(struct extent_map_tree *tree) +{ + struct extent_map *em; + + /* Avoid taking the write lock if we don't have any pending frees. */ + if (!test_and_clear_bit(EXTENT_MAP_TREE_PENDING_FREES, &tree->flags)) + return; + + write_lock(&tree->lock); + while ((em = list_first_entry_or_null(&tree->freed_extents, + struct extent_map, free_list))) { + list_del_init(&em->free_list); + write_unlock(&tree->lock); + free_extent_map(em); + cond_resched(); + write_lock(&tree->lock); + } + write_unlock(&tree->lock); +} + /* Do the math around the end of an extent, handling wrapping. */ static u64 range_end(u64 start, u64 len) { @@ -784,7 +851,7 @@ static void drop_all_extent_maps_fast(struct btrfs_inode *inode) em = rb_entry(node, struct extent_map, rb_node); em->flags &= ~(EXTENT_FLAG_PINNED | EXTENT_FLAG_LOGGING); btrfs_remove_extent_mapping(inode, em); - btrfs_free_extent_map(em); + btrfs_free_extent_map_safe(tree, em); if (cond_resched_rwlock_write(&tree->lock)) node = rb_first(&tree->root); @@ -792,6 +859,8 @@ static void drop_all_extent_maps_fast(struct btrfs_inode *inode) node = next; } write_unlock(&tree->lock); + + btrfs_free_pending_extent_maps(tree); } /* @@ -986,13 +1055,14 @@ void btrfs_drop_extent_map_range(struct btrfs_inode *inode, u64 start, u64 end, btrfs_free_extent_map(em); next: /* Once for us (for our lookup reference). */ - btrfs_free_extent_map(em); + btrfs_free_extent_map_safe(em_tree, em); em = next_em; } write_unlock(&em_tree->lock); + btrfs_free_pending_extent_maps(em_tree); btrfs_free_extent_map(split); btrfs_free_extent_map(split2); } diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h index 6f685f3c9327..a962012be1c3 100644 --- a/fs/btrfs/extent_map.h +++ b/fs/btrfs/extent_map.h @@ -97,11 +97,18 @@ struct extent_map { u32 flags; refcount_t refs; struct list_head list; + struct list_head free_list; +}; + +enum extent_map_flags { + EXTENT_MAP_TREE_PENDING_FREES, }; struct extent_map_tree { struct rb_root root; + unsigned long flags; struct list_head modified_extents; + struct list_head freed_extents; rwlock_t lock; }; @@ -175,6 +182,9 @@ int btrfs_split_extent_map(struct btrfs_inode *inode, u64 start, u64 len, u64 pr struct extent_map *btrfs_alloc_extent_map(void); void btrfs_free_extent_map(struct extent_map *em); +void btrfs_free_extent_map_safe(struct extent_map_tree *tree, + struct extent_map *em); +void btrfs_free_pending_extent_maps(struct extent_map_tree *tree); int __init btrfs_extent_map_init(void); void __cold btrfs_extent_map_exit(void); int btrfs_unpin_extent_cache(struct btrfs_inode *inode, u64 start, u64 len, u64 gen); diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index 9123adafa0d1..e6cd475057db 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -5410,7 +5410,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, */ if (ret) { btrfs_clear_em_logging(inode, em); - btrfs_free_extent_map(em); + btrfs_free_extent_map_safe(tree, em); continue; } @@ -5419,11 +5419,13 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans, ret = log_one_extent(trans, inode, em, path, ctx); write_lock(&tree->lock); btrfs_clear_em_logging(inode, em); - btrfs_free_extent_map(em); + btrfs_free_extent_map_safe(tree, em); } WARN_ON(!list_empty(&extents)); write_unlock(&tree->lock); + btrfs_free_pending_extent_maps(tree); + if (!ret) ret = btrfs_log_prealloc_extents(trans, inode, path, ctx); if (ret) -- 2.53.0