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: [<ffffffff81318c89>] dump_stack+0x67/0x9e [<ffffffff810810b0>] ___might_sleep+0xf0/0x140 [<ffffffff81081153>] __might_sleep+0x53/0xb0 [<ffffffff8126c1dc>] ext4_commit_super+0x19c/0x290 [<ffffffff8126e61a>] __ext4_grp_locked_error+0x14a/0x230 [<ffffffff81081153>] ? __might_sleep+0x53/0xb0 [<ffffffff812822be>] 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@xxxxxxxxxxxxxxx Reported-by: Nikolay Borisov <kernel@xxxxxxxx> Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) 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) -- 2.11.0.rc0.7.gbe5a750 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html