From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-179.mta1.migadu.com (out-179.mta1.migadu.com [95.215.58.179]) (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 1BA22371871 for ; Thu, 19 Mar 2026 09:46:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.179 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773913564; cv=none; b=n/3Wjtb8C1um6hUe304Xb+N9RfDEkya5LD32ijqPV3Go/SVsVrmEiOBMqJE5mXijKgfMDQaLwP01yKWhSGnP6cfaXOECIFTsD57l4SyJsD9sCKmR4cLkvSzN3oQCbRowRg+GVSURF5UWb/ybvcthG3zkYMmKuimSHqj7+82IHk8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773913564; c=relaxed/simple; bh=cRN8EZjN0h2+jxrX7Qg7Nt/GA5wUk3GLC0ZFOSeTKc4=; h=From:To:Cc:Subject:Date:Message-Id; b=hi/adczWd529Z7gujWpd0fVxGXKnQmi+koTWnZec/M8ZFPsNQl+gZOhdZqqD9upLd/ut9FsE41uKrcmJgs2Uxr6bnAm72j6YqlpAgrtVUu3TEUieR+blPicE/5OmVk1i7yUx9bLEgfvQUgG4Dc8H6fksjJbbrDNvEBrAd9EIMSw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=gQnorrAO; arc=none smtp.client-ip=95.215.58.179 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="gQnorrAO" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773913559; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc; bh=PRS+C2ToCgbemfPo3OczL8/mKw2zny7KVfM+D8nRAvA=; b=gQnorrAO7XzS4L74gu0g7oxcdTcX/kV1+Ix09t+jSUlIJp5qqTieHkpK/vcrQJoDVNHHmW KdXl2AIdeYaQmpD8tPgszqt9eJOfO5FyBONLluKSxOEhD86Wx4lT52AzWX2DCrElqiquXs EVQvF+A/dDkK7DevYpIFWSH+ufgWNds= From: Zqiang To: tytso@mit.edu, adilger.kernel@dilger.ca, libaokun@linux.alibaba.com Cc: linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, qiang.zhang@linux.dev Subject: [PATCH] ext4: Fix the might_sleep() warnings in kvfree() Date: Thu, 19 Mar 2026 17:45:45 +0800 Message-Id: <20260319094545.19291-1-qiang.zhang@linux.dev> X-Migadu-Flow: FLOW_OUT Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Use the kvfree() in the RCU read critical section can trigger the following warnings: EXT4-fs (vdb): unmounting filesystem cd983e5b-3c83-4f5a-a136-17b00eb9d018. WARNING: suspicious RCU usage ./include/linux/rcupdate.h:409 Illegal context switch in RCU read-side critical section! other info that might help us debug this: rcu_scheduler_active = 2, debug_locks = 1 Call Trace: dump_stack_lvl+0xbb/0xd0 dump_stack+0x14/0x20 lockdep_rcu_suspicious+0x15a/0x1b0 __might_resched+0x375/0x4d0 ? put_object.part.0+0x2c/0x50 __might_sleep+0x108/0x160 vfree+0x58/0x910 ? ext4_group_desc_free+0x27/0x270 kvfree+0x23/0x40 ext4_group_desc_free+0x111/0x270 ext4_put_super+0x3c8/0xd40 generic_shutdown_super+0x14c/0x4a0 ? __pfx_shrinker_free+0x10/0x10 kill_block_super+0x40/0x90 ext4_kill_sb+0x6d/0xb0 deactivate_locked_super+0xb4/0x180 deactivate_super+0x7e/0xa0 cleanup_mnt+0x296/0x3e0 __cleanup_mnt+0x16/0x20 task_work_run+0x157/0x250 ? __pfx_task_work_run+0x10/0x10 ? exit_to_user_mode_loop+0x6a/0x550 exit_to_user_mode_loop+0x102/0x550 do_syscall_64+0x44a/0x500 entry_SYSCALL_64_after_hwframe+0x77/0x7f BUG: sleeping function called from invalid context at mm/vmalloc.c:3441 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 556, name: umount preempt_count: 1, expected: 0 CPU: 3 UID: 0 PID: 556 Comm: umount Call Trace: dump_stack_lvl+0xbb/0xd0 dump_stack+0x14/0x20 __might_resched+0x275/0x4d0 ? put_object.part.0+0x2c/0x50 __might_sleep+0x108/0x160 vfree+0x58/0x910 ? ext4_group_desc_free+0x27/0x270 kvfree+0x23/0x40 ext4_group_desc_free+0x111/0x270 ext4_put_super+0x3c8/0xd40 generic_shutdown_super+0x14c/0x4a0 ? __pfx_shrinker_free+0x10/0x10 kill_block_super+0x40/0x90 ext4_kill_sb+0x6d/0xb0 deactivate_locked_super+0xb4/0x180 deactivate_super+0x7e/0xa0 cleanup_mnt+0x296/0x3e0 __cleanup_mnt+0x16/0x20 task_work_run+0x157/0x250 ? __pfx_task_work_run+0x10/0x10 ? exit_to_user_mode_loop+0x6a/0x550 exit_to_user_mode_loop+0x102/0x550 do_syscall_64+0x44a/0x500 entry_SYSCALL_64_after_hwframe+0x77/0x7f The above scenarios occur in initialization failures and teardown paths, there are no parallel operations on the resources released by kvfree(), this commit therefore remove rcu_read_lock/unlock() and use rcu_access_pointer() instead of rcu_dereference() operations. Fixes: 7c990728b99e ("ext4: fix potential race between s_flex_groups online resizing and access") Fixes: df3da4ea5a0f ("ext4: fix potential race between s_group_info online resizing and access") Signed-off-by: Zqiang --- fs/ext4/mballoc.c | 10 +++------- fs/ext4/super.c | 8 ++------ 2 files changed, 5 insertions(+), 13 deletions(-) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 20e9fdaf4301..e96513cc6151 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -3580,9 +3580,7 @@ static int ext4_mb_init_backend(struct super_block *sb) rcu_read_unlock(); iput(sbi->s_buddy_cache); err_freesgi: - rcu_read_lock(); - kvfree(rcu_dereference(sbi->s_group_info)); - rcu_read_unlock(); + kvfree(rcu_access_pointer(sbi->s_group_info)); return -ENOMEM; } @@ -3897,7 +3895,8 @@ void ext4_mb_release(struct super_block *sb) WARN_ON_ONCE(!list_empty(&sbi->s_discard_list)); } - if (sbi->s_group_info) { + group_info = rcu_access_pointer(sbi->s_group_info); + if (group_info) { for (i = 0; i < ngroups; i++) { cond_resched(); grinfo = ext4_get_group_info(sb, i); @@ -3915,12 +3914,9 @@ void ext4_mb_release(struct super_block *sb) num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) - 1) >> EXT4_DESC_PER_BLOCK_BITS(sb); - rcu_read_lock(); - group_info = rcu_dereference(sbi->s_group_info); for (i = 0; i < num_meta_group_infos; i++) kfree(group_info[i]); kvfree(group_info); - rcu_read_unlock(); } ext4_mb_avg_fragment_size_destroy(sbi); ext4_mb_largest_free_orders_destroy(sbi); diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 43f680c750ae..0b2fa7bd787f 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -1254,12 +1254,10 @@ static void ext4_group_desc_free(struct ext4_sb_info *sbi) struct buffer_head **group_desc; int i; - rcu_read_lock(); - group_desc = rcu_dereference(sbi->s_group_desc); + group_desc = rcu_access_pointer(sbi->s_group_desc); for (i = 0; i < sbi->s_gdb_count; i++) brelse(group_desc[i]); kvfree(group_desc); - rcu_read_unlock(); } static void ext4_flex_groups_free(struct ext4_sb_info *sbi) @@ -1267,14 +1265,12 @@ static void ext4_flex_groups_free(struct ext4_sb_info *sbi) struct flex_groups **flex_groups; int i; - rcu_read_lock(); - flex_groups = rcu_dereference(sbi->s_flex_groups); + flex_groups = rcu_access_pointer(sbi->s_flex_groups); if (flex_groups) { for (i = 0; i < sbi->s_flex_groups_allocated; i++) kvfree(flex_groups[i]); kvfree(flex_groups); } - rcu_read_unlock(); } static void ext4_put_super(struct super_block *sb) -- 2.17.1