On 2018-07-18 13:04, Chris Murphy wrote:
On Wed, Jul 18, 2018 at 7:30 AM, Austin S. Hemmelgarn
<ahferro...@gmail.com> wrote:
I'm not sure. In this particular case, this will fail on BTRFS for any X
larger than just short of one third of the total free space. I would expect
it to fail for any X larger than just short of half instead.
I'm confused. I can't get it to fail when X is 3/4 of free space.
lvcreate -V 2g -T vg/thintastic -n btrfstest
mkfs.btrfs -M /dev/mapper/vg-btrfstest
mount /dev/mapper/vg-btrfstest /mnt/btrfs
cd /mnt/btrfs
fallocate -l 1500m tmp
dd if=/dev/zero of=/mnt/btrfs/tmp bs=1M count=1450
Succeeds. No enospc. This is on kernel 4.17.6.
Odd, I could have sworn it would fail reliably. Unless something has
changed since I last tested though, doing it with X equal to the free
space on the filesystem will fail.
Copied from terminal:
[chris@f28s btrfs]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-btrfstest 2.0G 17M 2.0G 1% /mnt/btrfs
[chris@f28s btrfs]$ sudo fallocate -l 1500m /mnt/btrfs/tmp
[chris@f28s btrfs]$ filefrag -v tmp
Filesystem type is: 9123683e
File size of tmp is 1572864000 (384000 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 32767: 16400.. 49167: 32768: unwritten
1: 32768.. 65535: 56576.. 89343: 32768: 49168: unwritten
2: 65536.. 98303: 109824.. 142591: 32768: 89344: unwritten
3: 98304.. 131071: 163072.. 195839: 32768: 142592: unwritten
4: 131072.. 163839: 216320.. 249087: 32768: 195840: unwritten
5: 163840.. 196607: 269568.. 302335: 32768: 249088: unwritten
6: 196608.. 229375: 322816.. 355583: 32768: 302336: unwritten
7: 229376.. 262143: 376064.. 408831: 32768: 355584: unwritten
8: 262144.. 294911: 429312.. 462079: 32768: 408832: unwritten
9: 294912.. 327679: 482560.. 515327: 32768: 462080: unwritten
10: 327680.. 344063: 89344.. 105727: 16384: 515328: unwritten
11: 344064.. 360447: 142592.. 158975: 16384: 105728: unwritten
12: 360448.. 376831: 195840.. 212223: 16384: 158976: unwritten
13: 376832.. 383999: 249088.. 256255: 7168: 212224:
last,unwritten,eof
tmp: 14 extents found
[chris@f28s btrfs]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-btrfstest 2.0G 1.5G 543M 74% /mnt/btrfs
[chris@f28s btrfs]$ sudo dd if=/dev/zero of=/mnt/btrfs/tmp bs=1M count=1450
1450+0 records in
1450+0 records out
1520435200 bytes (1.5 GB, 1.4 GiB) copied, 13.4757 s, 113 MB/s
[chris@f28s btrfs]$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg-btrfstest 2.0G 1.5G 591M 72% /mnt/btrfs
[chris@f28s btrfs]$ filefrag -v tmp
Filesystem type is: 9123683e
File size of tmp is 1520435200 (371200 blocks of 4096 bytes)
ext: logical_offset: physical_offset: length: expected: flags:
0: 0.. 16383: 302336.. 318719: 16384:
1: 16384.. 32767: 355584.. 371967: 16384: 318720:
2: 32768.. 49151: 408832.. 425215: 16384: 371968:
3: 49152.. 65535: 462080.. 478463: 16384: 425216:
4: 65536.. 73727: 515328.. 523519: 8192: 478464:
5: 73728.. 86015: 3328.. 15615: 12288: 523520:
6: 86016.. 98303: 256256.. 268543: 12288: 15616:
7: 98304.. 104959: 49168.. 55823: 6656: 268544:
8: 104960.. 109047: 105728.. 109815: 4088: 55824:
9: 109048.. 113143: 158976.. 163071: 4096: 109816:
10: 113144.. 117239: 212224.. 216319: 4096: 163072:
11: 117240.. 121335: 318720.. 322815: 4096: 216320:
12: 121336.. 125431: 371968.. 376063: 4096: 322816:
13: 125432.. 128251: 425216.. 428035: 2820: 376064:
14: 128252.. 131071: 478464.. 481283: 2820: 428036:
15: 131072.. 132409: 1460.. 2797: 1338: 481284:
16: 132410.. 165177: 322816.. 355583: 32768: 2798:
17: 165178.. 197945: 376064.. 408831: 32768: 355584:
18: 197946.. 230713: 429312.. 462079: 32768: 408832:
19: 230714.. 263481: 482560.. 515327: 32768: 462080:
20: 263482.. 296249: 16400.. 49167: 32768: 515328:
21: 296250.. 327687: 56576.. 88013: 31438: 49168:
22: 327688.. 328711: 428036.. 429059: 1024: 88014:
23: 328712.. 361479: 109824.. 142591: 32768: 429060:
24: 361480.. 371199: 88014.. 97733: 9720: 142592: last,eof
tmp: 25 extents found
[chris@f28s btrfs]$
*shrug*
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