Hello! On Tue 23-08-22 12:16:46, Boyang Xue wrote: > On the latest kernel 6.0.0-0.rc2, I find the user quota limit in an > ext4 mount is unstable, that after several successful "write file then > delete" loops, it will finally fail with "Disk quota exceeded". This > bug can be reproduced on at least kernel-6.0.0-0.rc2 and > kernel-5.14.0-*, but can't be reproduced on kernel-4.18.0 based RHEL8 > kernel. <snip reproducer> > Run log on kernel-6.0.0-0.rc2 > ``` > (...skip successful Run#[1-2]...) > *** Run#3 *** > --- Quota before writing file --- > Disk quotas for user quota_test_user1 (uid 1003): > Filesystem blocks quota limit grace files quota limit grace > /dev/loop0 0 200000 300000 0 2000 3000 > --- --- > dd: error writing '/mntpt/test_300m': Disk quota exceeded > 299997+0 records in > 299996+0 records out > 307195904 bytes (307 MB, 293 MiB) copied, 1.44836 s, 212 MB/s So this shows that we have failed allocating the last filesystem block. I suspect this happens because the file gets allocted from several free space extens and so one extra indirect tree block needs to be allocated (or something like that). To verify that you can check the created file with "filefrag -v". Anyway I don't think it is quite correct to assume the filesystem can fit 300000 data blocks within 300000 block quota because the metadata overhead gets accounted into quota as well and the user has no direct control over that. So you should probably give filesystem some slack space in your tests for metadata overhead. > --- Quota after writing file --- > Disk quotas for user quota_test_user1 (uid 1003): > Filesystem blocks quota limit grace files quota limit grace > /dev/loop0 300000* 200000 300000 7days 1 2000 3000 > --- --- > --- Quota after deleting file --- > Disk quotas for user quota_test_user1 (uid 1003): > Filesystem blocks quota limit grace files quota limit grace > /dev/loop0 0 200000 300000 0 2000 3000 > --- --- > ``` Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR
