On Tue, 2009-06-16 at 10:00 +0200, Jens Axboe wrote: > On Tue, Jun 16 2009, Zhang, Yanmin wrote: > > On Fri, 2009-06-12 at 14:54 +0200, Jens Axboe wrote: > > > Hi, > > > > > > Here's the 10th version of the writeback patches. Changes since v9: > > > > > > - Fix bdi task exit race leaving work on the list, flush it after we > > > know we cannot be found anymore. > > > - Rename flusher tasks from bdi-foo to flush-foo. Should make it more > > > clear to the casual observer. > > > - Fix a problem with the btrfs bdi register patch that would spew > > > warnings for > 1 mounted btrfs file system. > > > - Rebase to current -git, there were some conflicts with the latest work > > > from viro/hch. > > > - Fix a block layer core problem were stacked devices would overwrite > > > the bdi state, causing problems and warning spew. > > > - In bdi_writeback_all(), in the race occurence of a work allocation > > > failure, restart scanning from the beginning. Then we can drop the > > > bdi_lock mutex before diving into bdi specific writeback. > > > - Convert bdi_lock to a spinlock. > > > - Use spin_trylock() in bdi_writeback_all(), if this isn't a data > > > integrity writeback. Debatable, I kind of like it... > > > - Get rid of BDI_CAP_FLUSH_FORKER, just check for match with the > > > default_backing_dev_info. > > > - Fix race in list checking in bdi_forker_task(). > > > > > > > > > For ease of patching, I've put the full diff here: > > > > > > http://kernel.dk/writeback-v10.patch > > Jens, > > > > I applied the patch to 2.6.30 and got a confliction. The attachment is > > the patch I ported to 2.6.30. Did I miss anything? > > > > > > With the patch, kernel reports below messages on 2 machines. > > > > INFO: task sync:29984 blocked for more than 120 seconds. > > "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > sync D ffff88002805e300 6168 29984 24581 > > ffff88022f84b780 0000000000000082 7fffffffffffffff ffff880133dbfe70 > > 0000000000000000 ffff88022e2b4c50 ffff88022e2b4fd8 00000001000c7bb8 > > ffff88022f513fd0 ffff880133dbfde8 ffff880133dbfec8 ffff88022d5d13c8 > > Call Trace: > > [<ffffffff802b69e4>] ? bdi_sched_wait+0x0/0xd > > [<ffffffff80780fde>] ? schedule+0x9/0x1d > > [<ffffffff802b69ed>] ? bdi_sched_wait+0x9/0xd > > [<ffffffff8078158d>] ? __wait_on_bit+0x40/0x6f > > [<ffffffff802b69e4>] ? bdi_sched_wait+0x0/0xd > > [<ffffffff80781628>] ? out_of_line_wait_on_bit+0x6c/0x78 > > [<ffffffff8024a426>] ? wake_bit_function+0x0/0x23 > > [<ffffffff802b67ac>] ? bdi_writeback_all+0x12a/0x152 > > [<ffffffff802b6805>] ? generic_sync_sb_inodes+0x31/0xde > > [<ffffffff802b6935>] ? sync_inodes_sb+0x83/0x88 > > [<ffffffff802b6980>] ? __sync_inodes+0x46/0x8f > > [<ffffffff802b94f2>] ? do_sync+0x36/0x5a > > [<ffffffff802b9538>] ? sys_sync+0xe/0x12 > > [<ffffffff8020b9ab>] ? system_call_fastpath+0x16/0x1b > > I don't think it is your backport, for some reason the v10 missed a > change that I think could solve this race. If not, there's another in > there that I need to look at. > > So against your current base, could you try with the below added as > well? The printk() is just so we can see if this triggers for you or > not. > > diff --git a/mm/backing-dev.c b/mm/backing-dev.c > index b3e80c5..a065da5 100644 > --- a/mm/backing-dev.c > +++ b/mm/backing-dev.c > @@ -384,6 +384,15 @@ static int bdi_start_fn(void *ptr) > */ > synchronize_srcu(&bdi->srcu); > > + /* > + * Flush any pending work. No more can be added, since > + * the bdi is no longer discoverable. > + */ > + if (!list_empty(&bdi->work_list)) { > + printk("bdi: flushing racy work\n"); I ran testings with the patch. 2 machines reported the same issues when do sync just after mounting filesystems for testing. These 2 machines did print out above info. One printed it just before dumping the blocking info. I ran a series of test cases. Every case does umount filesystems, then mount them again for testing. > + wb_do_writeback(wb); > + } > + > bdi_put_wb(bdi, wb); > return ret; > } > -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
