On 2017年12月06日 02:47, Andrei Borzenkov wrote: > 02.12.2017 03:27, Qu Wenruo пишет: >> >> That's the difference between how sub show and quota works. >> >> For quota, it's per-root owner check. >> Means even a file extent is shared between different inodes, if all >> inodes are inside the same subvolume, it's counted as exclusive. >> And if any of the file extent belongs to other subvolume, then it's >> counted as shared. >> > > Could you also explain how parent qgroup computes exclusive space? I.e. > > 10:~ # mkfs -t btrfs -f /dev/sdb1 > btrfs-progs v4.13.3 > See http://btrfs.wiki.kernel.org for more information. > > Performing full device TRIM /dev/sdb1 (1023.00MiB) ... > Label: (null) > UUID: b9b0643f-a248-4667-9e69-acf5baaef05b > Node size: 16384 > Sector size: 4096 > Filesystem size: 1023.00MiB > Block group profiles: > Data: single 8.00MiB > Metadata: DUP 51.12MiB > System: DUP 8.00MiB > SSD detected: no > Incompat features: extref, skinny-metadata > Number of devices: 1 > Devices: > ID SIZE PATH > 1 1023.00MiB /dev/sdb1 > > 10:~ # mount -t btrfs /dev/sdb1 /mnt > 10:~ # cd /mnt > 10:/mnt # btrfs quota enable . > 10:/mnt # btrfs su cre sub1 > Create subvolume './sub1' > 10:/mnt # dd if=/dev/urandom of=sub1/file1 bs=1K count=1024 > 1024+0 records in > 1024+0 records out > 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.00833739 s, 126 MB/s > 10:/mnt # dd if=/dev/urandom of=sub1/file2 bs=1K count=1024 > 1024+0 records in > 1024+0 records out > 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0179272 s, 58.5 MB/s > 10:/mnt # btrfs subvolume snapshot sub1 sub2 > Create a snapshot of 'sub1' in './sub2' > 10:/mnt # dd if=/dev/urandom of=sub2/file2 bs=1K count=1024 conv=notrunc > 1024+0 records in > 1024+0 records out > 1048576 bytes (1.0 MB, 1.0 MiB) copied, 0.0348762 s, 30.1 MB/s > 10:/mnt # btrfs qgroup show --sync -p . > qgroupid rfer excl parent > -------- ---- ---- ------ > 0/5 16.00KiB 16.00KiB --- > 0/256 2.02MiB 1.02MiB --- > 0/257 2.02MiB 1.02MiB --- > > So far so good. This is expected, each subvolume has 1MiB shared and > 1MiB exclusive. > > 10:/mnt # btrfs qgroup create 22/7 /mnt > 10:/mnt # btrfs qgroup assign --rescan 0/256 22/7 /mnt > Quota data changed, rescan scheduled > 10:/mnt # btrfs quota rescan -s /mnt > no rescan operation in progress > 10:/mnt # btrfs qgroup assign --rescan 0/257 22/7 /mnt > Quota data changed, rescan scheduled > 10:/mnt # btrfs quota rescan -s /mnt > no rescan operation in progress > 10:/mnt # btrfs qgroup show --sync -p . > qgroupid rfer excl parent > -------- ---- ---- ------ > 0/5 16.00KiB 16.00KiB --- > 0/256 2.02MiB 1.02MiB 22/7 > 0/257 2.02MiB 1.02MiB 22/7 > 22/7 3.03MiB 3.03MiB --- > 10:/mnt # > > Oops. Total for 22/7 is correct (1MiB shared + 2 * 1MiB exclusive) but > why all data is treated as exclusive here? It does not match your > explanation ...
Why? The qgroup calculates it correctly without problem. All extents in subvolume 256 and 257 belongs to qgroup 22/7. the 1M shared data all belongs to qgroup 22/7 so it's counted as exclusive. Not to mention the already exclusive extent from 0/256 and 0/257. The name "exclusive" just means, all referencer(s) of one extent are all in the qgroup. So the explanation is still correct. Please read btrfs-quota(8) 'SUBVOLUME QUOTA GROUPS' section for more details. Thanks, Qu >
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