From: David Sterba <dsterba@suse.cz>
To: Qu Wenruo <wqu@suse.com>
Cc: linux-btrfs@vger.kernel.org
Subject: Re: [PATCH v2 4/4] btrfs: subpage: pack all subpage bitmaps into a larger bitmap
Date: Mon, 23 Aug 2021 18:57:46 +0200 [thread overview]
Message-ID: <20210823165746.GH5047@twin.jikos.cz> (raw)
In-Reply-To: <20210817093852.48126-5-wqu@suse.com>
On Tue, Aug 17, 2021 at 05:38:52PM +0800, Qu Wenruo wrote:
> Currently we use u16 bitmap to make 4k sectorsize work for 64K page
> size.
>
> But this u16 bitmap is not large enough to contain larger page size like
> 128K, nor is space efficient for 16K page size.
>
> To handle both cases, here we pack all subpage bitmaps into a larger
> bitmap, now btrfs_subpage::bitmaps[] will be the ultimate bitmap for
> subpage usage.
>
> Each sub-bitmap will has its start bit number recorded in
> btrfs_subpage_info::*_start, and its bitmap length will be recorded in
> btrfs_subpage_info::bitmap_nr_bits.
>
> All subpage bitmap operations will be converted from using direct u16
> operations to bitmap operations, with above *_start calculated.
>
> For 64K page size with 4K sectorsize, this should not cause much
> difference.
>
> While for 16K page size, we will only need 1 unsigned long (u32) to
> store all the bitmaps, which saves quite some space.
>
> Furthermore, this allows us to support larger page size like 128K and
> 258K.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
> fs/btrfs/extent_io.c | 59 +++++++++++--------
> fs/btrfs/subpage.c | 136 +++++++++++++++++++++++++++++--------------
> fs/btrfs/subpage.h | 19 +-----
> 3 files changed, 129 insertions(+), 85 deletions(-)
>
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index 3c5770d47a95..fcb25ff86ea9 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -3856,10 +3856,9 @@ static void find_next_dirty_byte(struct btrfs_fs_info *fs_info,
> struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
> u64 orig_start = *start;
> /* Declare as unsigned long so we can use bitmap ops */
> - unsigned long dirty_bitmap;
> unsigned long flags;
> - int nbits = (orig_start - page_offset(page)) >> fs_info->sectorsize_bits;
> - int range_start_bit = nbits;
> + int range_start_bit = fs_info->subpage_info->dirty_offset +
> + (offset_in_page(orig_start) >> fs_info->sectorsize_bits);
There are several instances of fs_info->subpage_info so that warrants a
temporary variable.
> int range_end_bit;
>
> /*
> @@ -3874,11 +3873,14 @@ static void find_next_dirty_byte(struct btrfs_fs_info *fs_info,
>
> /* We should have the page locked, but just in case */
> spin_lock_irqsave(&subpage->lock, flags);
> - dirty_bitmap = subpage->dirty_bitmap;
> + bitmap_next_set_region(subpage->bitmaps, &range_start_bit, &range_end_bit,
> + fs_info->subpage_info->dirty_offset +
> + fs_info->subpage_info->bitmap_nr_bits);
> spin_unlock_irqrestore(&subpage->lock, flags);
>
> - bitmap_next_set_region(&dirty_bitmap, &range_start_bit, &range_end_bit,
> - BTRFS_SUBPAGE_BITMAP_SIZE);
> + range_start_bit -= fs_info->subpage_info->dirty_offset;
> + range_end_bit -= fs_info->subpage_info->dirty_offset;
> +
> *start = page_offset(page) + range_start_bit * fs_info->sectorsize;
> *end = page_offset(page) + range_end_bit * fs_info->sectorsize;
> }
> @@ -4602,12 +4604,11 @@ static int submit_eb_subpage(struct page *page,
> int submitted = 0;
> u64 page_start = page_offset(page);
> int bit_start = 0;
> - const int nbits = BTRFS_SUBPAGE_BITMAP_SIZE;
> int sectors_per_node = fs_info->nodesize >> fs_info->sectorsize_bits;
> int ret;
>
> /* Lock and write each dirty extent buffers in the range */
> - while (bit_start < nbits) {
> + while (bit_start < fs_info->subpage_info->bitmap_nr_bits) {
> struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
> struct extent_buffer *eb;
> unsigned long flags;
> @@ -4623,7 +4624,8 @@ static int submit_eb_subpage(struct page *page,
> break;
> }
> spin_lock_irqsave(&subpage->lock, flags);
> - if (!((1 << bit_start) & subpage->dirty_bitmap)) {
> + if (!test_bit(bit_start + fs_info->subpage_info->dirty_offset,
> + subpage->bitmaps)) {
> spin_unlock_irqrestore(&subpage->lock, flags);
> spin_unlock(&page->mapping->private_lock);
> bit_start++;
> @@ -7170,32 +7172,41 @@ void memmove_extent_buffer(const struct extent_buffer *dst,
> }
> }
>
> +#define GANG_LOOKUP_SIZE 16
> static struct extent_buffer *get_next_extent_buffer(
> struct btrfs_fs_info *fs_info, struct page *page, u64 bytenr)
> {
> - struct extent_buffer *gang[BTRFS_SUBPAGE_BITMAP_SIZE];
> + struct extent_buffer *gang[GANG_LOOKUP_SIZE];
> struct extent_buffer *found = NULL;
> u64 page_start = page_offset(page);
> - int ret;
> - int i;
> + u64 cur = page_start;
>
> ASSERT(in_range(bytenr, page_start, PAGE_SIZE));
> - ASSERT(PAGE_SIZE / fs_info->nodesize <= BTRFS_SUBPAGE_BITMAP_SIZE);
> lockdep_assert_held(&fs_info->buffer_lock);
>
> - ret = radix_tree_gang_lookup(&fs_info->buffer_radix, (void **)gang,
> - bytenr >> fs_info->sectorsize_bits,
> - PAGE_SIZE / fs_info->nodesize);
> - for (i = 0; i < ret; i++) {
> - /* Already beyond page end */
> - if (gang[i]->start >= page_start + PAGE_SIZE)
> - break;
> - /* Found one */
> - if (gang[i]->start >= bytenr) {
> - found = gang[i];
> - break;
> + while (cur < page_start + PAGE_SIZE) {
> + int ret;
> + int i;
> +
> + ret = radix_tree_gang_lookup(&fs_info->buffer_radix,
> + (void **)gang, cur >> fs_info->sectorsize_bits,
> + min_t(unsigned int, GANG_LOOKUP_SIZE,
> + PAGE_SIZE / fs_info->nodesize));
> + if (ret == 0)
> + goto out;
> + for (i = 0; i < ret; i++) {
> + /* Already beyond page end */
> + if (gang[i]->start >= page_start + PAGE_SIZE)
> + goto out;
> + /* Found one */
> + if (gang[i]->start >= bytenr) {
> + found = gang[i];
> + goto out;
> + }
> }
> + cur = gang[ret - 1]->start + gang[ret - 1]->len;
> }
> +out:
> return found;
> }
>
> diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
> index c4fb2ce52207..578095c52a0f 100644
> --- a/fs/btrfs/subpage.c
> +++ b/fs/btrfs/subpage.c
> @@ -142,10 +142,13 @@ struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
> enum btrfs_subpage_type type)
> {
> struct btrfs_subpage *ret;
> + unsigned int real_size;
>
> ASSERT(fs_info->sectorsize < PAGE_SIZE);
>
> - ret = kzalloc(sizeof(struct btrfs_subpage), GFP_NOFS);
> + real_size = struct_size(ret, bitmaps,
> + BITS_TO_LONGS(fs_info->subpage_info->total_nr_bits));
> + ret = kzalloc(real_size, GFP_NOFS);
> if (!ret)
> return ERR_PTR(-ENOMEM);
>
> @@ -328,37 +331,60 @@ void btrfs_page_end_writer_lock(const struct btrfs_fs_info *fs_info,
> unlock_page(page);
> }
>
> -/*
> - * Convert the [start, start + len) range into a u16 bitmap
> - *
> - * For example: if start == page_offset() + 16K, len = 16K, we get 0x00f0.
> - */
> -static u16 btrfs_subpage_calc_bitmap(const struct btrfs_fs_info *fs_info,
> - struct page *page, u64 start, u32 len)
> +static bool bitmap_test_range_all_set(unsigned long *addr, unsigned int start,
> + unsigned int nbits)
> {
> - const int bit_start = offset_in_page(start) >> fs_info->sectorsize_bits;
> - const int nbits = len >> fs_info->sectorsize_bits;
> + unsigned int found_zero;
>
> - btrfs_subpage_assert(fs_info, page, start, len);
> + found_zero = find_next_zero_bit(addr, start + nbits, start);
> + if (found_zero == start + nbits)
> + return true;
> + return false;
> +}
>
> - /*
> - * Here nbits can be 16, thus can go beyond u16 range. We make the
> - * first left shift to be calculate in unsigned long (at least u32),
> - * then truncate the result to u16.
> - */
> - return (u16)(((1UL << nbits) - 1) << bit_start);
> +static bool bitmap_test_range_all_zero(unsigned long *addr, unsigned int start,
> + unsigned int nbits)
> +{
> + unsigned int found_set;
> +
> + found_set = find_next_bit(addr, start + nbits, start);
> + if (found_set == start + nbits)
> + return true;
> + return false;
> }
>
> +#define subpage_calc_start_bit(fs_info, page, name, start, len) \
> +({ \
> + unsigned int start_bit; \
> + \
> + btrfs_subpage_assert(fs_info, page, start, len); \
> + start_bit = offset_in_page(start) >> fs_info->sectorsize_bits; \
> + start_bit += fs_info->subpage_info->name##_offset; \
> + start_bit; \
> +})
> +
> +#define subpage_test_bitmap_all_set(fs_info, subpage, name) \
> + bitmap_test_range_all_set(subpage->bitmaps, \
> + fs_info->subpage_info->name##_offset, \
> + fs_info->subpage_info->bitmap_nr_bits)
> +
> +#define subpage_test_bitmap_all_zero(fs_info, subpage, name) \
> + bitmap_test_range_all_zero(subpage->bitmaps, \
> + fs_info->subpage_info->name##_offset, \
> + fs_info->subpage_info->bitmap_nr_bits)
> +
> void btrfs_subpage_set_uptodate(const struct btrfs_fs_info *fs_info,
> struct page *page, u64 start, u32 len)
> {
> struct btrfs_subpage *subpage = (struct btrfs_subpage *)page->private;
> - const u16 tmp = btrfs_subpage_calc_bitmap(fs_info, page, start, len);
> + unsigned int start_bit = subpage_calc_start_bit(fs_info, page,
> + uptodate, start, len);
> unsigned long flags;
>
> spin_lock_irqsave(&subpage->lock, flags);
> - subpage->uptodate_bitmap |= tmp;
> - if (subpage->uptodate_bitmap == U16_MAX)
> + bitmap_set(subpage->bitmaps, start_bit,
> + len >> fs_info->sectorsize_bits);
All the bitmap_* calls like this and the parameter fit one line.
next prev parent reply other threads:[~2021-08-23 17:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-17 9:38 [PATCH v2 0/2] btrfs: subpage: pack all subpage bitmaps into a larger bitmap Qu Wenruo
2021-08-17 9:38 ` [PATCH v2 1/4] btrfs: only call btrfs_alloc_subpage() when sectorsize is smaller than PAGE_SIZE Qu Wenruo
2021-08-17 9:38 ` [PATCH v2 2/4] btrfs: make btrfs_alloc_subpage() to return struct btrfs_subpage * directly Qu Wenruo
2021-08-17 9:38 ` [PATCH v2 3/4] btrfs: introduce btrfs_subpage_bitmap_info Qu Wenruo
2021-08-17 10:11 ` Nikolay Borisov
2021-08-23 16:45 ` David Sterba
2021-08-30 14:28 ` Nikolay Borisov
2021-08-23 16:41 ` David Sterba
2021-08-23 23:15 ` Qu Wenruo
2021-08-17 9:38 ` [PATCH v2 4/4] btrfs: subpage: pack all subpage bitmaps into a larger bitmap Qu Wenruo
2021-08-17 13:43 ` Nikolay Borisov
2021-08-23 17:00 ` David Sterba
2021-08-23 16:57 ` David Sterba [this message]
2021-08-23 23:16 ` Qu Wenruo
2021-08-24 14:20 ` David Sterba
2021-08-17 13:44 ` [PATCH v2 0/2] " Nikolay Borisov
2021-08-23 17:05 ` David Sterba
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