From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 92DF920C012; Wed, 25 Feb 2026 01:46:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771984003; cv=none; b=rVgjiPqacRSmfJlI/ENBDF7d+JcCyYqu77jS8uq8NHDk8LyiS9SOvRRrb+LY8EaTlQENBkIOuTMD+IJn3Idi62llgQ5F0TMpdi9gS8UhN5F6PEND6RCRs3YVwD87KZa+dncwiSTl+6BDYXaHdMkEyq4LGhmqa0nC9/+fik57xhU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771984003; c=relaxed/simple; bh=Pb/iuWcjPYK0cSeXmAO4tGDQpgkkc9ZK9q8GC8XU998=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=O3u7hrQ/gU3HXmIkhJe5REsRVKjOM+pIuFiD+Jq/gBJjbm4JQ4IZlASS5be4Lm4zI413j3C5TbmOcaPYzsWySGdP41W2OzZmQaWGSLhaFQhv0Tip763wceET11hTVBIE16brcdWipf2l3qsNMig+j2W7xSaLzxkuUtWYaL+fazQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=IntCbekh; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="IntCbekh" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B224C116D0; Wed, 25 Feb 2026 01:46:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1771984003; bh=Pb/iuWcjPYK0cSeXmAO4tGDQpgkkc9ZK9q8GC8XU998=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IntCbekh4v5WH/6mD+tnjhr5jQOtQu5hsOSm2rDGeYanSCandI53IALA6vU/XE6DU OpBwS30GT5LNJ3i1LcmWCC42vLo+Pu3H6UgEmDabwigfD/Z1iLXV2aYhT7AECqwUpF PhfviwgU24yCdG3rrR1XDvAAJL1ajl3v6IkfqJSI= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Li Chen , Baokun Li , Zhang Yi , Jan Kara , Theodore Tso , Sasha Levin Subject: [PATCH 6.18 255/641] ext4: fast commit: make s_fc_lock reclaim-safe Date: Tue, 24 Feb 2026 17:19:41 -0800 Message-ID: <20260225012355.020044422@linuxfoundation.org> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260225012348.915798704@linuxfoundation.org> References: <20260225012348.915798704@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Li Chen [ Upstream commit 491f2927ae097e2d405afe0b3fe841931ab8aad2 ] s_fc_lock can be acquired from inode eviction and thus is reclaim unsafe. Since the fast commit path holds s_fc_lock while writing the commit log, allocations under the lock can enter reclaim and invert the lock order with fs_reclaim. Add ext4_fc_lock()/ext4_fc_unlock() helpers which acquire s_fc_lock under memalloc_nofs_save()/restore() context and use them everywhere so allocations under the lock cannot recurse into filesystem reclaim. Fixes: 6593714d67ba ("ext4: hold s_fc_lock while during fast commit") Signed-off-by: Li Chen Reviewed-by: Baokun Li Reviewed-by: Zhang Yi Reviewed-by: Jan Kara Link: https://patch.msgid.link/20260106120621.440126-1-me@linux.beauty Signed-off-by: Theodore Ts'o Signed-off-by: Sasha Levin --- fs/ext4/ext4.h | 16 ++++++++++++++ fs/ext4/fast_commit.c | 51 ++++++++++++++++++++++++------------------- 2 files changed, 44 insertions(+), 23 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 57087da6c7bee..933297251f66a 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -1771,6 +1771,10 @@ struct ext4_sb_info { * Main fast commit lock. This lock protects accesses to the * following fields: * ei->i_fc_list, s_fc_dentry_q, s_fc_q, s_fc_bytes, s_fc_bh. + * + * s_fc_lock can be taken from reclaim context (inode eviction) and is + * thus reclaim unsafe. Use ext4_fc_lock()/ext4_fc_unlock() helpers + * when acquiring / releasing the lock. */ struct mutex s_fc_lock; struct buffer_head *s_fc_bh; @@ -1815,6 +1819,18 @@ static inline void ext4_writepages_up_write(struct super_block *sb, int ctx) percpu_up_write(&EXT4_SB(sb)->s_writepages_rwsem); } +static inline int ext4_fc_lock(struct super_block *sb) +{ + mutex_lock(&EXT4_SB(sb)->s_fc_lock); + return memalloc_nofs_save(); +} + +static inline void ext4_fc_unlock(struct super_block *sb, int ctx) +{ + memalloc_nofs_restore(ctx); + mutex_unlock(&EXT4_SB(sb)->s_fc_lock); +} + static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino) { return ino == EXT4_ROOT_INO || diff --git a/fs/ext4/fast_commit.c b/fs/ext4/fast_commit.c index fa66b08de9994..5bd57d7f921b9 100644 --- a/fs/ext4/fast_commit.c +++ b/fs/ext4/fast_commit.c @@ -231,16 +231,16 @@ static bool ext4_fc_disabled(struct super_block *sb) void ext4_fc_del(struct inode *inode) { struct ext4_inode_info *ei = EXT4_I(inode); - struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); struct ext4_fc_dentry_update *fc_dentry; wait_queue_head_t *wq; + int alloc_ctx; if (ext4_fc_disabled(inode->i_sb)) return; - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(inode->i_sb); if (list_empty(&ei->i_fc_list) && list_empty(&ei->i_fc_dilist)) { - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(inode->i_sb, alloc_ctx); return; } @@ -275,9 +275,9 @@ void ext4_fc_del(struct inode *inode) #endif prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE); if (ext4_test_inode_state(inode, EXT4_STATE_FC_FLUSHING_DATA)) { - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(inode->i_sb, alloc_ctx); schedule(); - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(inode->i_sb); } finish_wait(wq, &wait.wq_entry); } @@ -288,7 +288,7 @@ void ext4_fc_del(struct inode *inode) * dentry create references, since it is not needed to log it anyways. */ if (list_empty(&ei->i_fc_dilist)) { - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(inode->i_sb, alloc_ctx); return; } @@ -298,7 +298,7 @@ void ext4_fc_del(struct inode *inode) list_del_init(&fc_dentry->fcd_dilist); WARN_ON(!list_empty(&ei->i_fc_dilist)); - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(inode->i_sb, alloc_ctx); release_dentry_name_snapshot(&fc_dentry->fcd_name); kmem_cache_free(ext4_fc_dentry_cachep, fc_dentry); @@ -315,6 +315,7 @@ void ext4_fc_mark_ineligible(struct super_block *sb, int reason, handle_t *handl tid_t tid; bool has_transaction = true; bool is_ineligible; + int alloc_ctx; if (ext4_fc_disabled(sb)) return; @@ -329,12 +330,12 @@ void ext4_fc_mark_ineligible(struct super_block *sb, int reason, handle_t *handl has_transaction = false; read_unlock(&sbi->s_journal->j_state_lock); } - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); is_ineligible = ext4_test_mount_flag(sb, EXT4_MF_FC_INELIGIBLE); if (has_transaction && (!is_ineligible || tid_gt(tid, sbi->s_fc_ineligible_tid))) sbi->s_fc_ineligible_tid = tid; ext4_set_mount_flag(sb, EXT4_MF_FC_INELIGIBLE); - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); WARN_ON(reason >= EXT4_FC_REASON_MAX); sbi->s_fc_stats.fc_ineligible_reason_count[reason]++; } @@ -358,6 +359,7 @@ static int ext4_fc_track_template( struct ext4_inode_info *ei = EXT4_I(inode); struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); tid_t tid = 0; + int alloc_ctx; int ret; tid = handle->h_transaction->t_tid; @@ -373,14 +375,14 @@ static int ext4_fc_track_template( if (!enqueue) return ret; - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(inode->i_sb); if (list_empty(&EXT4_I(inode)->i_fc_list)) list_add_tail(&EXT4_I(inode)->i_fc_list, (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING || sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING) ? &sbi->s_fc_q[FC_Q_STAGING] : &sbi->s_fc_q[FC_Q_MAIN]); - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(inode->i_sb, alloc_ctx); return ret; } @@ -402,6 +404,7 @@ static int __track_dentry_update(handle_t *handle, struct inode *inode, struct inode *dir = dentry->d_parent->d_inode; struct super_block *sb = inode->i_sb; struct ext4_sb_info *sbi = EXT4_SB(sb); + int alloc_ctx; spin_unlock(&ei->i_fc_lock); @@ -425,7 +428,7 @@ static int __track_dentry_update(handle_t *handle, struct inode *inode, take_dentry_name_snapshot(&node->fcd_name, dentry); INIT_LIST_HEAD(&node->fcd_dilist); INIT_LIST_HEAD(&node->fcd_list); - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); if (sbi->s_journal->j_flags & JBD2_FULL_COMMIT_ONGOING || sbi->s_journal->j_flags & JBD2_FAST_COMMIT_ONGOING) list_add_tail(&node->fcd_list, @@ -446,7 +449,7 @@ static int __track_dentry_update(handle_t *handle, struct inode *inode, WARN_ON(!list_empty(&ei->i_fc_dilist)); list_add_tail(&node->fcd_dilist, &ei->i_fc_dilist); } - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); spin_lock(&ei->i_fc_lock); return 0; @@ -1046,18 +1049,19 @@ static int ext4_fc_perform_commit(journal_t *journal) struct blk_plug plug; int ret = 0; u32 crc = 0; + int alloc_ctx; /* * Step 1: Mark all inodes on s_fc_q[MAIN] with * EXT4_STATE_FC_FLUSHING_DATA. This prevents these inodes from being * freed until the data flush is over. */ - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { ext4_set_inode_state(&iter->vfs_inode, EXT4_STATE_FC_FLUSHING_DATA); } - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); /* Step 2: Flush data for all the eligible inodes. */ ret = ext4_fc_flush_data(journal); @@ -1067,7 +1071,7 @@ static int ext4_fc_perform_commit(journal_t *journal) * any error from step 2. This ensures that waiters waiting on * EXT4_STATE_FC_FLUSHING_DATA can resume. */ - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { ext4_clear_inode_state(&iter->vfs_inode, EXT4_STATE_FC_FLUSHING_DATA); @@ -1084,7 +1088,7 @@ static int ext4_fc_perform_commit(journal_t *journal) * prepare_to_wait() in ext4_fc_del(). */ smp_mb(); - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); /* * If we encountered error in Step 2, return it now after clearing @@ -1101,12 +1105,12 @@ static int ext4_fc_perform_commit(journal_t *journal) * previous handles are now drained. We now mark the inodes on the * commit queue as being committed. */ - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); list_for_each_entry(iter, &sbi->s_fc_q[FC_Q_MAIN], i_fc_list) { ext4_set_inode_state(&iter->vfs_inode, EXT4_STATE_FC_COMMITTING); } - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); jbd2_journal_unlock_updates(journal); /* @@ -1117,6 +1121,7 @@ static int ext4_fc_perform_commit(journal_t *journal) blkdev_issue_flush(journal->j_fs_dev); blk_start_plug(&plug); + alloc_ctx = ext4_fc_lock(sb); /* Step 6: Write fast commit blocks to disk. */ if (sbi->s_fc_bytes == 0) { /* @@ -1134,7 +1139,6 @@ static int ext4_fc_perform_commit(journal_t *journal) } /* Step 6.2: Now write all the dentry updates. */ - mutex_lock(&sbi->s_fc_lock); ret = ext4_fc_commit_dentry_updates(journal, &crc); if (ret) goto out; @@ -1156,7 +1160,7 @@ static int ext4_fc_perform_commit(journal_t *journal) ret = ext4_fc_write_tail(sb, crc); out: - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); blk_finish_plug(&plug); return ret; } @@ -1290,6 +1294,7 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid) struct ext4_sb_info *sbi = EXT4_SB(sb); struct ext4_inode_info *ei; struct ext4_fc_dentry_update *fc_dentry; + int alloc_ctx; if (full && sbi->s_fc_bh) sbi->s_fc_bh = NULL; @@ -1297,7 +1302,7 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid) trace_ext4_fc_cleanup(journal, full, tid); jbd2_fc_release_bufs(journal); - mutex_lock(&sbi->s_fc_lock); + alloc_ctx = ext4_fc_lock(sb); while (!list_empty(&sbi->s_fc_q[FC_Q_MAIN])) { ei = list_first_entry(&sbi->s_fc_q[FC_Q_MAIN], struct ext4_inode_info, @@ -1356,7 +1361,7 @@ static void ext4_fc_cleanup(journal_t *journal, int full, tid_t tid) if (full) sbi->s_fc_bytes = 0; - mutex_unlock(&sbi->s_fc_lock); + ext4_fc_unlock(sb, alloc_ctx); trace_ext4_fc_stats(sb); } -- 2.51.0