On Thu, Jun 18 2009, Zhang, Yanmin wrote: > On Thu, 2009-06-18 at 07:13 +0200, Jens Axboe wrote: > > On Thu, Jun 18 2009, Zhang, Yanmin wrote: > > > On Tue, 2009-06-16 at 21:53 +0200, Jens Axboe wrote: > > > > On Tue, Jun 16 2009, 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. > > > > > > > > OK that wont work, since we need to actually wait for the work to be > > > > flushed, otherwise we wreak things when we free the bdi immediately > > > > after that. > > > > > > > > Can you try with this patch? > > > Jens, > > > > > > I tested below patch on 4 machines (run all fio sub-test cases twice which > > > need more than 10 hours). The previous 2 machines don't stop this time. > > > Unfortunately, the 3rd machine stops. I double-check the disassembled codes > > > of kernel and make sure bdi_start_fn really calls wb_do_writeback. > > > > Sorry I should have made that more clear when posting v11. This patch > > wont fully solve the problem, however the v11 patch series should. So if > > you test with that, hopefully all soft hangs should be gone. > Ok. I will start new testing against V11. I also add some debugging codes into > V11. Great, thanks! There's a small issue with v11 that you should be aware of. The test for bdi_add_default_flusher_task() was inverted. I'm attaching a diff at the end. The interesting bit is the 2nd hunk of backing-dev.c, the others are just a cleanup. diff --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h index 6815f8b..e623c57 100644 --- a/include/linux/backing-dev.h +++ b/include/linux/backing-dev.h @@ -107,7 +107,6 @@ void bdi_start_writeback(struct backing_dev_info *bdi, struct super_block *sb, long nr_pages, enum writeback_sync_modes sync_mode); int bdi_writeback_task(struct bdi_writeback *wb); void bdi_writeback_all(struct super_block *sb, struct writeback_control *wbc); -void bdi_add_default_flusher_task(struct backing_dev_info *bdi); void bdi_add_flusher_task(struct backing_dev_info *bdi); int bdi_has_dirty_io(struct backing_dev_info *bdi); diff --git a/mm/backing-dev.c b/mm/backing-dev.c index b4517ee..c2eec72 100644 --- a/mm/backing-dev.c +++ b/mm/backing-dev.c @@ -37,6 +37,8 @@ static int bdi_sync_supers(void *); static void sync_supers_timer_fn(unsigned long); static void arm_supers_timer(void); +static void bdi_add_default_flusher_task(struct backing_dev_info *bdi); + #ifdef CONFIG_DEBUG_FS #include <linux/debugfs.h> #include <linux/seq_file.h> @@ -496,7 +498,7 @@ static int bdi_forker_task(void *ptr) list_for_each_entry_safe(bdi, tmp, &bdi_list, bdi_list) { if (bdi->wb.task) continue; - if (!list_empty(&bdi->work_list) && + if (list_empty(&bdi->work_list) && !bdi_has_dirty_io(bdi)) continue; @@ -607,7 +609,7 @@ static int flusher_add_helper_test(struct backing_dev_info *bdi) * Add the default flusher task that gets created for any bdi * that has dirty data pending writeout */ -void bdi_add_default_flusher_task(struct backing_dev_info *bdi) +void static bdi_add_default_flusher_task(struct backing_dev_info *bdi) { bdi_add_one_flusher_task(bdi, flusher_add_helper_test); } -- Jens Axboe -- 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
