On 2012/12/7 1:09, Jan Kara wrote: > On Fri 07-12-12 00:21:25, qixuan wu wrote: >> Hi Kara, >> >> On Thu, Dec 6, 2012 at 8:37 PM, Jan Kara <jack@xxxxxxx> wrote: >>> On Thu 06-12-12 09:13:45, Li Zefan wrote: >>>>>> I found this in one log: >>>>>> >>>>>> Nov 14 05:26:55 kernel: EXT3-fs error (device sda7): ext3_readdir: bad entry in directory #7225391: rec_len is smaller than minimal - offset=3952, inode=0, rec_len=0, name_len=0 >>>>>> Nov 14 13:42:40 kernel: EXT3-fs error (device sda7): ext3_readdir: bad entry in directory #7225391: rec_len is smaller than minimal - offset=4024, inode=0, rec_len=0, name_len=0 >>>>>> Nov 16 17:29:40 kernel: EXT3-fs error (device sda7): ext3_readdir: bad entry in directory #7225391: rec_len is smaller than minimal - offset=4084, inode=0, rec_len=0, name_len=0 >>>>>> Nov 23 19:42:44 kernel: EXT3-fs error (device sda7): ext3_readdir: bad entry in directory #7225391: rec_len is smaller than minimal - offset=3952, inode=0, rec_len=0, name_len=0 >>> Sorry for posting here in the thread but I got unsubscribed from the >>> list so I don't have the beginning of the thread in my inbox. >>> >>> ext3 directory format is such that the last directory entry in the block >>> should have length to exactly fill up the whole block. Apparently, the >>> length got trimmed for some reason so we ended up before end of directory >>> block looked of another directory entry there and didn't find anything. I >>> will also make one observation regarding offsets. They are 3952, 4024, and >>> 4084. If we subtract that from 4096 (block size), we get differences (in >>> binary) 10010000, 01001000, 00001100. Interestingly these have always two >>> bits set. Might be luck but need not... >> >> Yes, we also found the interesting things that the offset happen in >> many boards are like below: >> 1) 3952 >> 2) 3988( 3952+36) >> 3) 4024( 3988+36) >> 4) 4048(4042+24) >> 5) 4084(same as the rec_len of ".." file if there isn't any file). >> >> I need introduce the rule of the files in the dir, for example: >> . >> .. >> current_log.txt (len is 15, rec_len is 24 when there is file after it, >> the value "24" i think has relative with offset 4048) >> 20120526124556.865213.txt(len is 25, rec_len is 36 when there is file after it). >> 20120526124984.239475.txt(len is 25, rec_len is 36 when there is file after it). >> .... >> Because the rec_len is 36, it has some relative with those offset >> values( the diff of those values are multiple of 36). >> I need tell another thing, customer's app invoke opendir/readdir very >> frequently. There are more than 1000 times, every second(the value >> need to be confirmed). >> >>> Anyway it would be interesting to get the dump of the corrupted directory >>> before e2fsck is run. You can do that by running: >>> debugfs -R "dump_inode <7225391> /tmp/corrupted_dir" /dev/sda7 >>> >>> Then you can send the dump of the corrupted directory here. >> >> We have already dump of the data by debugfs. The data is very good >> without error. But we just did it before fsck, even the fsck is not >> giving any error. I want to know whether fsck will modify disk data >> without reporting any error or not ? > Ah, OK. So it seems that directory block is OK, just f_pos gets corrupted > somehow. There are guards in ext3_readdir() to rescan dir block when > directory is modified but maybe that's not working correctly. I don't want > to burn too much time on this since this is so ancient kernel but I'd be > looking in that direction... > I've added some debug code into ext3, which does these things: - dump the dir block - print the current and last f_pos and offset - dump_stack() to see which process triggers the bug Hope we can trigger the bug in our labs (We did see this happened twice this week in a lab), though we can't patch the kernel in the products. I compared ext3_readdir() with latest ext3, and saw no difference except some API changes. I'll dig deeper. Thansks for the suggestion! Regards Li Zefan -- 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
