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author | Qu Wenruo <wqu@suse.com> | 2024-02-17 16:59:49 +1030 |
---|---|---|
committer | David Sterba <dsterba@suse.com> | 2024-03-05 17:13:23 +0100 |
commit | 8e7e9c672fd810a099dc2ac92a80e8e95cd5b0dc (patch) | |
tree | 60a6f6d218ebc78fea0016aae795d72bffb40bbc /fs/btrfs/subpage.c | |
parent | 621b9ff18c009ed6512df93b63fcf7dbac4cb4e0 (diff) | |
download | linux-stable-8e7e9c672fd810a099dc2ac92a80e8e95cd5b0dc.tar.gz linux-stable-8e7e9c672fd810a099dc2ac92a80e8e95cd5b0dc.tar.bz2 linux-stable-8e7e9c672fd810a099dc2ac92a80e8e95cd5b0dc.zip |
btrfs: subpage: make reader lock utilize bitmap
Currently btrfs_subpage utilizes its atomic member @reader to manage the
reader counter. However it is only utilized to prevent the page to be
released/unlocked when we still have reads underway.
In that use case, we don't really allow multiple readers on the same
subpage sector. So here we can introduce a new locked bitmap to
represent exactly which subpage range is locked for read.
In theory we can remove btrfs_subpage::reader as it's just the set bits
of the new locked bitmap. But unfortunately bitmap doesn't provide such
handy API yet, so we still keep the reader counter.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/subpage.c')
-rw-r--r-- | fs/btrfs/subpage.c | 45 |
1 files changed, 35 insertions, 10 deletions
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c index 24f8be565a61..eae9e8a478f6 100644 --- a/fs/btrfs/subpage.c +++ b/fs/btrfs/subpage.c @@ -111,6 +111,9 @@ void btrfs_init_subpage_info(struct btrfs_subpage_info *subpage_info, u32 sector subpage_info->checked_offset = cur; cur += nr_bits; + subpage_info->locked_offset = cur; + cur += nr_bits; + subpage_info->total_nr_bits = cur; } @@ -237,28 +240,58 @@ static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info, start + len <= folio_pos(folio) + PAGE_SIZE); } +#define subpage_calc_start_bit(fs_info, folio, name, start, len) \ +({ \ + unsigned int start_bit; \ + \ + btrfs_subpage_assert(fs_info, folio, start, len); \ + start_bit = offset_in_page(start) >> fs_info->sectorsize_bits; \ + start_bit += fs_info->subpage_info->name##_offset; \ + start_bit; \ +}) + void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len) { struct btrfs_subpage *subpage = folio_get_private(folio); + const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len); const int nbits = len >> fs_info->sectorsize_bits; + unsigned long flags; + btrfs_subpage_assert(fs_info, folio, start, len); + spin_lock_irqsave(&subpage->lock, flags); + /* + * Even though it's just for reading the page, no one should have + * locked the subpage range. + */ + ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits)); + bitmap_set(subpage->bitmaps, start_bit, nbits); atomic_add(nbits, &subpage->readers); + spin_unlock_irqrestore(&subpage->lock, flags); } void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info, struct folio *folio, u64 start, u32 len) { struct btrfs_subpage *subpage = folio_get_private(folio); + const int start_bit = subpage_calc_start_bit(fs_info, folio, locked, start, len); const int nbits = len >> fs_info->sectorsize_bits; + unsigned long flags; bool is_data; bool last; btrfs_subpage_assert(fs_info, folio, start, len); is_data = is_data_inode(folio->mapping->host); + + spin_lock_irqsave(&subpage->lock, flags); + + /* The range should have already been locked. */ + ASSERT(bitmap_test_range_all_set(subpage->bitmaps, start_bit, nbits)); ASSERT(atomic_read(&subpage->readers) >= nbits); + + bitmap_clear(subpage->bitmaps, start_bit, nbits); last = atomic_sub_and_test(nbits, &subpage->readers); /* @@ -270,6 +303,7 @@ void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info, */ if (is_data && last) folio_unlock(folio); + spin_unlock_irqrestore(&subpage->lock, flags); } static void btrfs_subpage_clamp_range(struct folio *folio, u64 *start, u32 *len) @@ -365,16 +399,6 @@ void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info, folio_unlock(folio); } -#define subpage_calc_start_bit(fs_info, folio, name, start, len) \ -({ \ - unsigned int start_bit; \ - \ - btrfs_subpage_assert(fs_info, folio, 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, \ @@ -751,6 +775,7 @@ void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info, GET_SUBPAGE_BITMAP(subpage, subpage_info, writeback, &writeback_bitmap); GET_SUBPAGE_BITMAP(subpage, subpage_info, ordered, &ordered_bitmap); GET_SUBPAGE_BITMAP(subpage, subpage_info, checked, &checked_bitmap); + GET_SUBPAGE_BITMAP(subpage, subpage_info, locked, &checked_bitmap); spin_unlock_irqrestore(&subpage->lock, flags); dump_page(folio_page(folio, 0), "btrfs subpage dump"); |