On Mon, Dec 09, 2019 at 09:52:54AM +0800, Qu Wenruo wrote: > > > On 2019/12/9 上午9:33, Zygo Blaxell wrote: > > On Sun, Dec 08, 2019 at 07:17:21PM -0500, Zygo Blaxell wrote: > >> On Sun, Dec 08, 2019 at 02:19:10PM -0500, Mike Gilbert wrote: > >>> Hello, > >>> > >>> I have a directory entry that cannot be stat-ed or unlinked. This > >>> issue persists across reboots, so it seems there is something wrong on > >>> disk. > >>> > >>> % ls -l /var/cache/ccache.bad/2/c > >>> ls: cannot access > >>> '/var/cache/ccache.bad/2/c/0390cb341d248c589c419007da68b2-7351.manifest': > >>> No such > >>> file or directory > >>> total 0 > >>> -????????? ? ? ? ? ? 0390cb341d248c589c419007da68b2-7351.manifest > >> > >> I have seen a bug similar to this some years ago. It was present as > >> far back as 4.5, and seems to still be present in 5.0.21. I don't have > >> detailed tracking information on it due to the low severity: not a crash > >> or data corruption bug, and workarounds exist both to prevent the bug > >> and to clean up its aftermath. > >> > >> The reproducer is something like: > >> > >> while (true) { // pseudocode > >> int fd = create(tmp_name); > >> write(fd, ...); > >> fsync(fd); // required, bug does not appear without this fsync > >> close(fd); > >> rename(tmp_name, regular_name); > >> } > >> > >> and a crash, maybe with some heavy write load. This is typical of > >> applications like git and ccache, and in the wild, broken directory > >> entries are often found in these applications' directories. > >> > >> Somewhere between 4.5 and 4.12 (a big range, I know), there was a change > >> in behavior: before, the broken directory entry could not be removed, > >> renamed, or used for a new file, the only way to get rid of the broken > >> directory entry was to delete the entire subvol. After the behavior > >> change, the broken directory entry could be removed by creating a new > >> file and renaming it to the broken directory entry name. > > > > I found a filesystem that currently has one of these broken dirents: > > > > root@tester24:/media/testfs/beeshome# ls -l > > ls: cannot access 'beesstats.txt.tmp': No such file or directory > > total 3446032 > > -rw-r--r-- 1 root root 10313 Nov 22 2018 all-df-today.png > > -rw-r--r-- 1 root root 3297813 Nov 22 2018 all-df-today.txt > > -rw------- 1 root root 1048488 Dec 7 17:35 beescrawl.dat > > -rwx------ 1 root root 1073741824 Dec 8 20:19 beeshash.dat > > -????????? ? ? ? ? ? beesstats.txt.tmp > > -rw-r--r-- 1 root root 16064406 Dec 3 00:13 df-2019-11-28.txt > > -rw-r--r-- 1 root root 4269887 Dec 5 00:52 df-2019-12-03.txt > > -rw-r--r-- 1 root root 6358158 Dec 7 16:44 df-2019-12-05.txt > > -rw-r--r-- 1 root root 3221101 Dec 8 20:18 df-2019-12-07.txt > > -rw-r--r-- 1 root root 2208475574 Dec 3 00:13 log-2019-11-28.txt > > -rw-r--r-- 1 root root 72372394 Dec 5 00:52 log-2019-12-03.txt > > -rw-r--r-- 1 root root 97472346 Dec 7 16:44 log-2019-12-05.txt > > -rw-r--r-- 1 root root 42378425 Dec 8 20:19 log-2019-12-07.txt > > lrwxrwxrwx 1 root root 18 Dec 7 17:35 log-today.txt -> log-2019-12-07.txt > > > > It seems I can create a file with the same name, and then I get two: > > > > root@tester24:/media/testfs/beeshome# date > beesstats.txt.tmp > > root@tester24:/media/testfs/beeshome# ls -l > > total 3446044 > > -rw-r--r-- 1 root root 10313 Nov 22 2018 all-df-today.png > > -rw-r--r-- 1 root root 3297813 Nov 22 2018 all-df-today.txt > > -rw------- 1 root root 1048488 Dec 7 17:35 beescrawl.dat > > -rwx------ 1 root root 1073741824 Dec 8 20:19 beeshash.dat > > -rw-r--r-- 1 root root 29 Dec 8 20:19 beesstats.txt.tmp > > -rw-r--r-- 1 root root 29 Dec 8 20:19 beesstats.txt.tmp > > -rw-r--r-- 1 root root 16064406 Dec 3 00:13 df-2019-11-28.txt > > -rw-r--r-- 1 root root 4269887 Dec 5 00:52 df-2019-12-03.txt > > -rw-r--r-- 1 root root 6358158 Dec 7 16:44 df-2019-12-05.txt > > -rw-r--r-- 1 root root 3221363 Dec 8 20:19 df-2019-12-07.txt > > -rw-r--r-- 1 root root 2208475574 Dec 3 00:13 log-2019-11-28.txt > > -rw-r--r-- 1 root root 72372394 Dec 5 00:52 log-2019-12-03.txt > > -rw-r--r-- 1 root root 97472346 Dec 7 16:44 log-2019-12-05.txt > > -rw-r--r-- 1 root root 42384027 Dec 8 20:19 log-2019-12-07.txt > > lrwxrwxrwx 1 root root 18 Dec 7 17:35 log-today.txt -> log-2019-12-07.txt > > root@tester24:/media/testfs/beeshome# cat beesstats.txt.tmp > > Sun Dec 8 20:19:38 EST 2019 > > > > dump-tree sees both DIR_INDEX but only one DIR_ITEM: > > > > item 9 key (256 DIR_ITEM 2721875446) itemoff 15740 itemsize 47 > > location key (133693 INODE_ITEM 0) type FILE > > transid 5002644 data_len 0 name_len 17 > > name: beesstats.txt.tmp > > item 18 key (256 DIR_INDEX 22037) itemoff 15332 itemsize 47 > > location key (11481 INODE_ITEM 0) type FILE > > transid 1876891 data_len 0 name_len 17 > > name: beesstats.txt.tmp > > item 32 key (256 DIR_INDEX 264858) itemoff 14684 itemsize 47 > > location key (133693 INODE_ITEM 0) type FILE > > transid 5002644 data_len 0 name_len 17 > > name: beesstats.txt.tmp > > > > but I can only delete DIR_ITEMs: > > > > root@tester24:/media/testfs/beeshome# rm beesstats.txt.tmp > > root@tester24:/media/testfs/beeshome# rm beesstats.txt.tmp > > rm: cannot remove 'beesstats.txt.tmp': No such file or directory > > root@tester24:/media/testfs/beeshome# ls -l > > ls: cannot access 'beesstats.txt.tmp': No such file or directory > > total 3446048 > > -rw-r--r-- 1 root root 10313 Nov 22 2018 all-df-today.png > > -rw-r--r-- 1 root root 3297813 Nov 22 2018 all-df-today.txt > > -rw------- 1 root root 1048488 Dec 7 17:35 beescrawl.dat > > -rwx------ 1 root root 1073741824 Dec 8 20:20 beeshash.dat > > -????????? ? ? ? ? ? beesstats.txt.tmp > > -rw-r--r-- 1 root root 16064406 Dec 3 00:13 df-2019-11-28.txt > > -rw-r--r-- 1 root root 4269887 Dec 5 00:52 df-2019-12-03.txt > > -rw-r--r-- 1 root root 6358158 Dec 7 16:44 df-2019-12-05.txt > > -rw-r--r-- 1 root root 3221494 Dec 8 20:19 df-2019-12-07.txt > > -rw-r--r-- 1 root root 2208475574 Dec 3 00:13 log-2019-11-28.txt > > -rw-r--r-- 1 root root 72372394 Dec 5 00:52 log-2019-12-03.txt > > -rw-r--r-- 1 root root 97472346 Dec 7 16:44 log-2019-12-05.txt > > -rw-r--r-- 1 root root 42396102 Dec 8 20:20 log-2019-12-07.txt > > lrwxrwxrwx 1 root root 18 Dec 7 17:35 log-today.txt -> log-2019-12-07.txt > > > > leaving the first DIR_INDEX behind: > > > > item 17 key (256 DIR_INDEX 22037) itemoff 15379 itemsize 47 > > location key (11481 INODE_ITEM 0) type FILE > > transid 1876891 data_len 0 name_len 17 > > name: beesstats.txt.tmp > > This looks like a older kernel bug (hopes so). > > So there is an orphan DIR_INDEX left, but never cleaned up properly. > > In that case, btrfs-progs should be able to repair it. > But strangely, why original mode check didn't report it? I'm not sure what you mean by "original mode check". I can't run btrfs check on this filesystem (97GB of metadata, too big for either regular or lowmem to handle in reasonable time). There used to be a stat check on the missing inode, which would fail in older kernels, and make the filename permanently unusable (until the subvol was deleted). That broke a lot of applications. The stat check was removed at some point, which is much better. > BTW, does that 11481 inode still exist? Nope, the only '11481' in the entire subvol's dump-tree output is that DIR_INDEX item. > Thanks, > Qu > > > > So the btrfs read side is fine, it's the writing side that is putting bad > > metadata on the disk. > > > >> Another workaround is to remove the fsync by running the application > >> under eatmydata. btrfs performs a flush in the rename() operation when > >> an existing file is replaced, so the fsync that triggers the bug was > >> not necessary in the first place. Note this only works when replacing > >> an existing file, so the flushoncommit mount option is required to make > >> this work in other cases. > >> > >>> % uname -a > >>> Linux naomi 4.19.67 #4 SMP Sun Aug 18 14:35:39 EDT 2019 x86_64 AMD > >>> Phenom(tm) II X6 1055T Processor > >>> AuthenticAMD GNU/Linux > >>> > >>> % btrfs --version > >>> btrfs-progs v5.4 > >>> > >>> I have tried running btrfs check, and I get differing results based on > >>> the --mode switch: > >>> > >>> # btrfs check --readonly /dev/sda3 > >>> [1/7] checking root items > >>> [2/7] checking extents > >>> [3/7] checking free space cache > >>> [4/7] checking fs roots > >>> [5/7] checking only csums items (without verifying data) > >>> [6/7] checking root refs > >>> [7/7] checking quota groups > >>> Opening filesystem to check... > >>> Checking filesystem on /dev/sda3 > >>> UUID: 5e9dcab6-036d-40f1-8b40-24ab4c062bf6 > >>> found 284337733632 bytes used, no error found > >>> total csum bytes: 267182280 > >>> total tree bytes: 4498915328 > >>> total fs tree bytes: 3972464640 > >>> total extent tree bytes: 199819264 > >>> btree space waste bytes: 776711635 > >>> file data blocks allocated: 313928671232 > >>> referenced 279141621760 > >>> > >>> # btrfs check --readonly --mode=lowmem /dev/sda3 > >>> [1/7] checking root items > >>> [2/7] checking extents > >>> [3/7] checking free space cache > >>> [4/7] checking fs roots > >>> ERROR: root 5 INODE_ITEM[4065004] index 18446744073709551615 name > >>> 0390cb341d248c589c419007da68b2-7351.manifest filetype 1 missing > >>> ERROR: root 5 DIR ITEM[486836 13905] name > >>> 0390cb341d248c589c419007da68b2-7351.manifest filetype 1 mismath > >>> ERROR: root 5 DIR ITEM[486836 2543451757] mismatch name > >>> 0390cb341d248c589c419007da68b2-7351.manifest filetype 1 > >>> ERROR: errors found in fs roots > >>> Opening filesystem to check... > >>> Checking filesystem on /dev/sda3 > >>> UUID: 5e9dcab6-036d-40f1-8b40-24ab4c062bf6 > >>> found 284337733632 bytes used, error(s) found > >>> total csum bytes: 267182280 > >>> total tree bytes: 4498915328 > >>> total fs tree bytes: 3972464640 > >>> total extent tree bytes: 199819264 > >>> btree space waste bytes: 776711635 > >>> file data blocks allocated: 313928671232 > >>> referenced 279141621760 > >>> > >>> Please advise on possible next steps to diagnose and fix this. > > > > >