Why was this selected? It is a new feature not a fix, it's not marked for a stable kernel and moreover it's incomplete (2327fb2e23416cfb2795ccca2f77d4d65925be99 is a prerequisite). I have the same question for the patches for 5.15 and 5.16. I think we should either drop it, or at the very least include the above mentioned commit as well. Thanks! -Lukas On Mon, Jan 17, 2022 at 09:40:07PM -0500, Sasha Levin wrote: > From: Lukas Czerner <lczerner@xxxxxxxxxx> > > [ Upstream commit 4a69aecbfb30a3fc85bf8028386c047d5607a97a ] > > Ext4 has an optimization mechanism for batched disacrd (FITRIM) that > should help speed up subsequent calls of FITRIM ioctl by skipping the > groups that were previously trimmed. However because the FITRIM allows > to set the minimum size of an extent to trim, ext4 stores the last > minimum extent size and only avoids trimming the group if it was > previously trimmed with minimum extent size equal to, or smaller than > the current call. > > There is currently no way to bypass the optimization without > umount/mount cycle. This becomes a problem when the file system is > live migrated to a different storage, because the optimization will > prevent possibly useful discard calls to the storage. > > Fix it by exporting the s_last_trim_minblks via sysfs interface which > will allow us to set the minimum size to the number of blocks larger > than subsequent FITRIM call, effectively bypassing the optimization. > > By setting the s_last_trim_minblks to ULONG_MAX the optimization will be > effectively cleared regardless of the previous state, or file system > configuration. > > For example: > getconf ULONG_MAX > /sys/fs/ext4/dm-1/last_trim_minblks > > Signed-off-by: Lukas Czerner <lczerner@xxxxxxxxxx> > Reported-by: Laurent GUERBY <laurent@xxxxxxxxxx> > Reviewed-by: Andreas Dilger <adilger@xxxxxxxxx> > Link: https://lore.kernel.org/r/20211103145122.17338-2-lczerner@xxxxxxxxxx > Signed-off-by: Theodore Ts'o <tytso@xxxxxxx> > Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> > --- > fs/ext4/sysfs.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/fs/ext4/sysfs.c b/fs/ext4/sysfs.c > index f24bef3be48a3..4192b4af10602 100644 > --- a/fs/ext4/sysfs.c > +++ b/fs/ext4/sysfs.c > @@ -250,6 +250,7 @@ EXT4_ATTR(last_error_time, 0444, last_error_time); > EXT4_ATTR(journal_task, 0444, journal_task); > EXT4_RW_ATTR_SBI_UI(mb_prefetch, s_mb_prefetch); > EXT4_RW_ATTR_SBI_UI(mb_prefetch_limit, s_mb_prefetch_limit); > +EXT4_RW_ATTR_SBI_UL(last_trim_minblks, s_last_trim_minblks); > > static unsigned int old_bump_val = 128; > EXT4_ATTR_PTR(max_writeback_mb_bump, 0444, pointer_ui, &old_bump_val); > @@ -299,6 +300,7 @@ static struct attribute *ext4_attrs[] = { > #endif > ATTR_LIST(mb_prefetch), > ATTR_LIST(mb_prefetch_limit), > + ATTR_LIST(last_trim_minblks), > NULL, > }; > ATTRIBUTE_GROUPS(ext4); > -- > 2.34.1 >
