Messages in this thread | | | Date | Tue, 21 Feb 2023 08:09:53 +0800 | Subject | Re: [PATCH v2 4/4] btrfs: replace btrfs_io_context::raid_map[] with a fixed u64 value | From | Qu Wenruo <> |
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On 2023/2/20 20:14, Geert Uytterhoeven wrote: > Hi Qu, > > On Mon, Feb 20, 2023 at 12:50 PM Qu Wenruo <quwenruo.btrfs@gmx.com> wrote: >> On 2023/2/20 16:53, Geert Uytterhoeven wrote: >>> On Tue, 7 Feb 2023, Qu Wenruo wrote: >>>> In btrfs_io_context structure, we have a pointer raid_map, which is to >>>> indicate the logical bytenr for each stripe. >>>> >>>> But considering we always call sort_parity_stripes(), the result >>>> raid_map[] is always sorted, thus raid_map[0] is always the logical >>>> bytenr of the full stripe. >>>> >>>> So why we waste the space and time (for sorting) for raid_map[]? >>>> >>>> This patch will replace btrfs_io_context::raid_map with a single u64 >>>> number, full_stripe_start, by: >>>> >>>> - Replace btrfs_io_context::raid_map with full_stripe_start >>>> >>>> - Replace call sites using raid_map[0] to use full_stripe_start >>>> >>>> - Replace call sites using raid_map[i] to compare with nr_data_stripes. >>>> >>>> The benefits are: >>>> >>>> - Less memory wasted on raid_map >>>> It's sizeof(u64) * num_stripes vs size(u64). >>>> It's always a save for at least one u64, and the benefit grows larger >>>> with num_stripes. >>>> >>>> - No more weird alloc_btrfs_io_context() behavior >>>> As there is only one fixed size + one variable length array. >>>> >>>> Signed-off-by: Qu Wenruo <wqu@suse.com> >>> >>> Thanks for your patch, which is now commit 4a8c6e8a6dc8ae4c ("btrfs: >>> replace btrfs_io_context::raid_map with a fixed u64 value") in >>> next-20230220. >>> >>> noreply@ellerman.id.au reported several build failures when >>> building for 32-bit platforms: >>> >>> ERROR: modpost: "__umoddi3" [fs/btrfs/btrfs.ko] undefined! >>> >>>> --- a/fs/btrfs/volumes.c >>>> +++ b/fs/btrfs/volumes.c >>>> @@ -6556,35 +6532,44 @@ int __btrfs_map_block(struct btrfs_fs_info >>>> *fs_info, enum btrfs_map_op op, >>>> } >>>> bioc->map_type = map->type; >>>> >>>> - for (i = 0; i < num_stripes; i++) { >>>> - set_io_stripe(&bioc->stripes[i], map, stripe_index, >>>> stripe_offset, >>>> - stripe_nr); >>>> - stripe_index++; >>>> - } >>>> - >>>> - /* Build raid_map */ >>>> + /* >>>> + * For RAID56 full map, we need to make sure the stripes[] follows >>>> + * the rule that data stripes are all ordered, then followed with P >>>> + * and Q (if we have). >>>> + * >>>> + * It's still mostly the same as other profiles, just with extra >>>> + * rotataion. >>>> + */ >>>> if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK && need_raid_map && >>>> (need_full_stripe(op) || mirror_num > 1)) { >>>> - u64 tmp; >>>> - unsigned rot; >>>> - >>>> - /* Work out the disk rotation on this stripe-set */ >>>> - rot = stripe_nr % num_stripes; >>>> - >>>> - /* Fill in the logical address of each stripe */ >>>> - tmp = stripe_nr * data_stripes; >>>> - for (i = 0; i < data_stripes; i++) >>>> - bioc->raid_map[(i + rot) % num_stripes] = >>>> - em->start + ((tmp + i) << BTRFS_STRIPE_LEN_SHIFT); >>>> - >>>> - bioc->raid_map[(i + rot) % map->num_stripes] = RAID5_P_STRIPE; >>>> - if (map->type & BTRFS_BLOCK_GROUP_RAID6) >>>> - bioc->raid_map[(i + rot + 1) % num_stripes] = >>>> - RAID6_Q_STRIPE; >>>> - >>>> - sort_parity_stripes(bioc, num_stripes); >>>> + /* >>>> + * For RAID56 @stripe_nr is already the number of full stripes >>>> + * before us, which is also the rotation value (needs to modulo >>>> + * with num_stripes). >>>> + * >>>> + * In this case, we just add @stripe_nr with @i, then do the >>>> + * modulo, to reduce one modulo call. >>>> + */ >>>> + bioc->full_stripe_logical = em->start + >>>> + ((stripe_nr * data_stripes) << BTRFS_STRIPE_LEN_SHIFT); >>>> + for (i = 0; i < num_stripes; i++) { >>>> + set_io_stripe(&bioc->stripes[i], map, >>>> + (i + stripe_nr) % num_stripes, >>> >>> As stripe_nr is u64, this is a 64-by-32 modulo operation, which >>> should be implemented using a helper from include/linux/math64.h >>> instead. >> >> This is an older version, in the latest version, the @stripe_nr variable >> is also u32, and I tried compiling the latest branch with i686, it >> doesn't cause any u64 division problems anymore. >> >> You can find the latest branch in either github or from the mailling list: >> >> https://github.com/adam900710/linux/tree/map_block_refactor >> >> https://lore.kernel.org/linux-btrfs/cover.1676611535.git.wqu@suse.com/ > > So the older version was "v2", and the latest version had no > version indicator, nor changelog, thus assuming v1? > No surprise people end up applying the wrong version...
The previous version is two separate patchsets, the new one is the merged one.
And I sent the merged version because the dependency problem and conflicts, and since it's the merged version, no changelog based on previous version.
Thanks, Qu
> > Gr{oetje,eeting}s, > > Geert >
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