Jan Kara <jack@xxxxxxx> writes: > On Thu 16-06-16 16:42:58, Nikola Pajkovsky wrote: >> Jan Kara <jack@xxxxxxx> writes: >> >> > On Fri 10-06-16 07:52:56, Nikola Pajkovsky wrote: >> >> Jan Kara <jack@xxxxxxx> writes: >> >> > On Thu 09-06-16 09:23:29, Nikola Pajkovsky wrote: >> >> >> Holger Hoffstätte <holger@xxxxxxxxxxxxxxxxxxxxxx> writes: >> >> >> >> >> >> > On Wed, 08 Jun 2016 14:56:31 +0200, Jan Kara wrote: >> >> >> > (snip) >> >> >> >> Attached patch fixes the issue for me. I'll submit it once a full xfstests >> >> >> >> run finishes for it (which may take a while as our server room is currently >> >> >> >> moving to a different place). >> >> >> >> >> >> >> >> Honza >> >> >> >> -- >> >> >> >> Jan Kara <jack@xxxxxxxx> >> >> >> >> SUSE Labs, CR >> >> >> >> From 3a120841a5d9a6c42bf196389467e9e663cf1cf8 Mon Sep 17 00:00:00 2001 >> >> >> >> From: Jan Kara <jack@xxxxxxx> >> >> >> >> Date: Wed, 8 Jun 2016 10:01:45 +0200 >> >> >> >> Subject: [PATCH] ext4: Fix deadlock during page writeback >> >> >> >> >> >> >> >> Commit 06bd3c36a733 (ext4: fix data exposure after a crash) uncovered a >> >> >> >> deadlock in ext4_writepages() which was previously much harder to hit. >> >> >> >> After this commit xfstest generic/130 reproduces the deadlock on small >> >> >> >> filesystems. >> >> >> > >> >> >> > Since you marked this for -stable, just a heads-up that the previous patch >> >> >> > for the data exposure was rejected from -stable (see [1]) because it >> >> >> > has the mismatching "!IS_NOQUOTA(inode) &&" line, which didn't exist >> >> >> > until 4.6. I removed it locally but Greg probably wants an official patch. >> >> >> > >> >> >> > So both this and the previous patch need to be submitted. >> >> >> > >> >> >> > [1] http://permalink.gmane.org/gmane.linux.kernel.stable/18074{4,5,6} >> >> >> >> >> >> I'm just wondering if the Jan's patch is not related to blocked >> >> >> processes in following trace. It very hard to hit it and I don't have >> >> >> any reproducer. >> >> > >> >> > This looks like a different issue. Does the machine recover itself or is it >> >> > a hard hang and you have to press a reset button? >> >> >> >> The machine is bit bigger than I have pretend. It's 18 vcpu with 160 GB >> >> ram and machine has dedicated mount point only for PostgreSQL data. >> >> >> >> Nevertheless, I was able always to ssh to the machine, so machine itself >> >> was not in hard hang and ext4 mostly gets recover by itself (it took >> >> 30min). But I have seen situation, were every process who 'touch' the ext4 >> >> goes immediately to D state and does not recover even after hour. >> > >> > If such situation happens, can you run 'echo w >/proc/sysrq-trigger' to >> > dump stuck processes and also run 'iostat -x 1' for a while to see how much >> > IO is happening in the system? That should tell us more. >> >> >> Link to 'echo w >/proc/sysrq-trigger' is here, because it's bit bigger >> to mail it. >> >> http://expirebox.com/download/68c26e396feb8c9abb0485f857ccea3a.html > > Can you upload it again please? I've got to looking at the file only today > and it is already deleted. Thanks! http://expirebox.com/download/c010e712e55938435c446cdc01a0b523.html >> I was running iotop and there was traffic roughly ~20 KB/s write. >> >> What was bit more interesting, was looking at >> >> cat /proc/vmstat | egrep "nr_dirty|nr_writeback" >> >> nr_drity had around 240 and was slowly counting up, but nr_writeback had >> ~8800 and was stuck for 120s. > > Hum, interesting. This would suggest like IO completion got stuck for some > reason. We'll see more from the stacktraces hopefully. I have monitor /sys/kernel/debug/bdi/253:32/stats for 10 mins per 1 sec. Values are all same as follows: --[ Sun Jun 19 06:11:08 CEST 2016 BdiWriteback: 15840 kB BdiReclaimable: 32320 kB BdiDirtyThresh: 0 kB DirtyThresh: 1048576 kB BackgroundThresh: 131072 kB BdiDirtied: 6131163680 kB BdiWritten: 6130214880 kB BdiWriteBandwidth: 324948 kBps b_dirty: 2 b_io: 3 b_more_io: 0 bdi_list: 1 state: c Maybe those values can cause issue and kicks in writeback to often and block everyone else. $ sysctl -a | grep dirty | grep -v ratio vm.dirty_background_bytes = 134217728 vm.dirty_bytes = 1073741824 vm.dirty_expire_centisecs = 1500 vm.dirty_writeback_centisecs = 500 I even have output of command, if you're interested. $ trace-cmd record -e ext4 -e jbd2 -e writeback -e block sleep 600 -- Nikola -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
