On 03/25, John wrote: > On Tue, Mar 24, 2020 at 9:01 PM Chao Yu <yuch...@huawei.com> wrote: > > I guess ssd should support discard, however I saw sdb was wrapped with > > device > > mapper, which may have different character, just want to check that whether > > device mapper disable the discard. > > > > If backup/restore is hard for you, how about let me add some logs on fstrim > > interface? then we could retry fstrim to see where we actually fail. > > I have an older totally different SSD for testing that seems to support > discard: > # hdparm -I /dev/sdc | grep TRIM > * Data Set Management TRIM supported (limit 8 blocks) > * Deterministic read ZEROs after TRIM > > As I test, I created two f2fs partitions on this different SSD: > 1) /dev/sdc2 normal F2FS > 2) /dev/sdc3 encrypted with LUKS (dm-crypt) then formatted to F2FS > > Results: > 1) Regular F2FS > # fstrim -v /regular > /regular: 0 B (0 bytes) trimmed
This is normal. > > 2) Encrypted F2FS > # fstrim -v /encrypted > fstrim: /encrypted: the discard operation is not supported It seems dm-crypt has discard-related support, ie., "allow_discards", in ctrl. But, FWIW, the target simply doesn't support discard at all. # grep discards_supported drivers/md/* drivers/md/dm-cache-target.c: ti->discards_supported = true; drivers/md/dm-clone-target.c: ti->discards_supported = true; drivers/md/dm-log-writes.c: ti->discards_supported = true; drivers/md/dm-table.c: if (!tgt->num_discard_bios && tgt->discards_supported) drivers/md/dm-table.c: DMWARN("%s: %s: ignoring discards_supported because num_discard_bios is zero.", drivers/md/dm-table.c: * 'discards_supported') or it relies on _all_ data devices having drivers/md/dm-table.c: if (!ti->discards_supported && drivers/md/dm-thin.c: * Setting 'discards_supported' circumvents the normal drivers/md/dm-thin.c: ti->discards_supported = true; drivers/md/dm-thin.c: ti->discards_supported = true; drivers/md/dm-zoned-target.c: ti->discards_supported = true; > > Can we conclude that the device mapper is some how spoofing fstrim > into thinking the device doesn't support trim? Happy to hear your > thoughts. > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel