From mboxrd@z Thu Jan 1 00:00:00 1970 From: He YunLei Subject: Re: Data lost in Android app for not write new checkpoint Date: Tue, 4 Aug 2015 21:16:21 +0800 Message-ID: <55C0BB25.1070208@huawei.com> References: <55BADD52.9060901@huawei.com> <01a401d0cb7e$bc483130$34d89390$@samsung.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1ZMc5N-00017o-7c for linux-f2fs-devel@lists.sourceforge.net; Tue, 04 Aug 2015 13:16:53 +0000 Received: from szxga01-in.huawei.com ([58.251.152.64]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1ZMc5H-0006Hj-8H for linux-f2fs-devel@lists.sourceforge.net; Tue, 04 Aug 2015 13:16:53 +0000 In-Reply-To: <01a401d0cb7e$bc483130$34d89390$@samsung.com> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Chao Yu Cc: 'Jaegeuk Kim' , linux-f2fs-devel@lists.sourceforge.net On 2015/7/31 18:49, Chao Yu wrote: > Hi Bintian, > >> -----Original Message----- >> From: He YunLei [mailto:heyunlei@huawei.com] >> Sent: Friday, July 31, 2015 10:29 AM >> To: linux-f2fs-devel@lists.sourceforge.net; Jaegeuk Kim >> Cc: Chao Yu; cm224.lee@samsung.com; Bintian >> Subject: [f2fs-dev] Data lost in Android app for not write new checkpoint >> >> Hi all, >> Recently I did some test with f2fs on my Android phone, and found a problem >> which I didn't know how to tackle it. >> I use my Android phone with /data partition formatted by mkfs.f2fs. When the >> phone just started, I check the f2fs status by reading the file /sys/kernel/debug/f2fs/status >> in debugfs. >> >> CP calls: 10 >> GC calls: 19 (BG: 19) >> - data segments : 19 (19) >> - node segments : 0 (0) >> >> We can see /data partition has done 10 times write_checkpoint since f2fs is mounted >> on the phone, it also has triggered 19 times background GC. >> >> ****** >> >> Here I took some photos consecutively, and check the file /sys/kernel/debug/f2fs/status again >> >> ****** >> >> CP calls: 10 >> GC calls: 20 (BG: 20) >> - data segments : 20 (20) >> - node segments : 0 (0) >> >> there is no change in CP calls number and background GC doesn't write new checkpoint. >> if then a sudden power failure or system crash occur, the photos will be lost when the phone >> restart, and a sync before crash will avoid the data lost. >> I think this problem is bad for user experience of using Android phone with f2fs. >> How do we deal with such situation? I wish you and other developers in this list could help >> me in a correct way. > > IMO, it's better to figure out whether this is a bug of f2fs first or not. > > You can enable some traces in f2fs to see whether fsync is called or not. > > enable trace by: > echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_sync_file_enter/enable > echo 1 > /sys/kernel/debug/tracing/events/f2fs/f2fs_sync_file_exit/enable > print trace by: > cat /sys/kernel/debug/tracing/trace > > If fsync is not be called, I think in ext4 there must be the same problem, > but I guess fortunately journal commit thread save its data since it commit > transaction per 5 second by default. You can try to configure (commit=nrsec) > it with larger value for verification the issue with ext4 filesystem. > I enable the event xxx_sync_file_enter both in f2fs and ext4, and find neither of them was triggered by photo files. Then I try f2fs_writepages and ext4_da_write_pages: ino file_name 65573 IMG_20150804_031619.jpg 65575 IMG_20150804_031619_1.jpg 65576 IMG_20150804_031620.jpg 65577 IMG_20150804_031620_1.jpg ext4_da_write_pages: dev 259,0 ino 65573 b_blocknr 0 b_size 0 b_state 0x0000 first_page 0 io_done 0 pages_written 0 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65575 b_blocknr 0 b_size 2408448 b_state 0x0221 first_page 0 io_done 1 pages_written 588 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65575 b_blocknr 0 b_size 0 b_state 0x0000 first_page 0 io_done 0 pages_written 0 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65576 b_blocknr 0 b_size 2428928 b_state 0x0221 first_page 0 io_done 1 pages_written 593 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65576 b_blocknr 0 b_size 0 b_state 0x0000 first_page 0 io_done 0 pages_written 0 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65577 b_blocknr 0 b_size 2383872 b_state 0x0221 first_page 0 io_done 1 pages_written 582 sync_mode 0 ext4_da_write_pages: dev 259,0 ino 65577 b_blocknr 0 b_size 0 b_state 0x0000 first_page 0 io_done 0 pages_written 0 sync_mode 0 f2fs_writepages doesn't appear in the test of f2fs I also try modify commit=300(default 5), but it doesn't work. Maybe somewhere else in ext4 launch the ext4_da_write_pages operation. At the end, I try to mount f2fs with disable_roll_forward, when system reboot, the f2fs is inconsistent, there are several failed check items in fsck. Thanks, He > As a quick thought, maybe we can add one commit data thread, periodically > writebacking user data written by user previously, then do checkpoint for > persistence. > > So by this way, at most, we just lose our data for last configured time of > commit period. > > Thanks, > >> >> Thanks, >> He > > > > . > ------------------------------------------------------------------------------