From: Theodore Ts'o Date: Mon, 14 Nov 2016 03:02:29 +0000 (-0500) Subject: ext4: don't lock buffer in ext4_commit_super if holding spinlock X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1566a48aaa10c6bb29b9a69dd8279f9a4fc41e35;p=linux-beck.git ext4: don't lock buffer in ext4_commit_super if holding spinlock If there is an error reported in mballoc via ext4_grp_locked_error(), the code is holding a spinlock, so ext4_commit_super() must not try to lock the buffer head, or else it will trigger a BUG: BUG: sleeping function called from invalid context at ./include/linux/buffer_head.h:358 in_atomic(): 1, irqs_disabled(): 0, pid: 993, name: mount CPU: 0 PID: 993 Comm: mount Not tainted 4.9.0-rc1-clouder1 #62 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.8.1-0-g4adadbd-20150316_085822-nilsson.home.kraxel.org 04/01/2014 ffff880006423548 ffffffff81318c89 ffffffff819ecdd0 0000000000000166 ffff880006423558 ffffffff810810b0 ffff880006423580 ffffffff81081153 ffff880006e5a1a0 ffff88000690e400 0000000000000000 ffff8800064235c0 Call Trace: [] dump_stack+0x67/0x9e [] ___might_sleep+0xf0/0x140 [] __might_sleep+0x53/0xb0 [] ext4_commit_super+0x19c/0x290 [] __ext4_grp_locked_error+0x14a/0x230 [] ? __might_sleep+0x53/0xb0 [] ext4_mb_generate_buddy+0x1de/0x320 Since ext4_grp_locked_error() calls ext4_commit_super with sync == 0 (and it is the only caller which does so), avoid locking and unlocking the buffer in this case. This can result in races with ext4_commit_super() if there are other problems (which is what commit 4743f83990614 was trying to address), but a Warning is better than BUG. Fixes: 4743f83990614 Cc: stable@vger.kernel.org # 4.9 Reported-by: Nikolay Borisov Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara --- diff --git a/fs/ext4/super.c b/fs/ext4/super.c index e4f61c39328a..ff6f3ab09c7e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4537,7 +4537,8 @@ static int ext4_commit_super(struct super_block *sb, int sync) &EXT4_SB(sb)->s_freeinodes_counter)); BUFFER_TRACE(sbh, "marking dirty"); ext4_superblock_csum_set(sb); - lock_buffer(sbh); + if (sync) + lock_buffer(sbh); if (buffer_write_io_error(sbh)) { /* * Oh, dear. A previous attempt to write the @@ -4553,8 +4554,8 @@ static int ext4_commit_super(struct super_block *sb, int sync) set_buffer_uptodate(sbh); } mark_buffer_dirty(sbh); - unlock_buffer(sbh); if (sync) { + unlock_buffer(sbh); error = __sync_dirty_buffer(sbh, test_opt(sb, BARRIER) ? WRITE_FUA : WRITE_SYNC); if (error)