4.9-stable review patch. If anyone has any objections, please let me know.
------------------ From: Theodore Ts'o <[email protected]> commit 1566a48aaa10c6bb29b9a69dd8279f9a4fc41e35 upstream. 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 Reported-by: Nikolay Borisov <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]> Reviewed-by: Jan Kara <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]> --- fs/ext4/super.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -4550,7 +4550,8 @@ static int ext4_commit_super(struct supe &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 @@ -4566,8 +4567,8 @@ static int ext4_commit_super(struct supe 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)
