The qgroup verification code can trivially be extended to provide
extended information on the extents which a subvolume root
references. Along with qgroup-verify, I have found this tool to be
invaluable when tracking down extent references.
The patch adds a switch to the check subcommand '--subvol-extents'
which takes as args a single subvolume id. When run with the switch,
we'll print out each extent that the subvolume references. The extent
printout gives standard extent info you would expect along with
information on which other roots reference it.
Sample output follows - this is a few lines from a run on a subvolume
I've been testing qgroup changes on:
Print extent state for subvolume 281 on /dev/vdb2
UUID: 8203ca66-9858-4e3f-b447-5bbaacf79c02
Offset Len Root Refs Roots
12582912 20480 12 257 279 280 281 282 283 284 285 286 287 288 289
12603392 8192 12 257 279 280 281 282 283 284 285 286 287 288 289
12611584 12288 12 257 279 280 281 282 283 284 285 286 287 288 289
<snip a bunch of extents to show some variety>
124583936 16384 4 281 282 283 280
125075456 16384 4 280 281 282 283
126255104 16384 11 257 280 281 282 283 284 285 286 287 288 289
4763508736 4096 3 279 280 281
In case it wasn't clear, this applies on top of my qgroup verify patch:
"btrfs-progs: add quota group verify code"
A branch with all this can be found on github:
https://github.com/markfasheh/btrfs-progs-patches/tree/qgroup-verify
Please apply,
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: David Sterba <dsterba@suse.cz>
This patch adds functionality (in qgroup-verify.c) to compute bytecounts in
subvolume quota groups. The original groups are read in and stored in memory
so that after we compute our own bytecounts, we can compare them with those
on disk. A print function is provided to do this comparison and show the
results on the console.
A 'qgroup check' pass is added to btrfsck. If any subvolume quota groups
differ from what we compute, the differences for them are printed. We also
provide an option '--qgroup-report' which will run only the quota check code
and print a report on all quota groups. Other than making it possible to
verify that our qgroup changes work correctly, this mode can also be used in
xfstests for automated checking after qgroup tests.
This patch does not address the following:
- compressed counts are identical to non compressed, because kernel doesn't
make the distinction yet. Adding the code to verify compressed counts
shouldn't be hard at all though once kernel can do this.
- It is only concerned with subvolume quota groups (like most of
btrfs-progs).
Signed-off-by: Mark Fasheh <mfasheh@suse.de>
Signed-off-by: David Sterba <dsterba@suse.cz>
Mark Fasheh