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btrfs: subpage: make writer lock utilize bitmap

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For the writer counter, it's pretty much the same as the reader counter,
and they are exclusive.  So move them to the new locked bitmap.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Qu Wenruo 2024-02-17 16:59:50 +10:30 committed by David Sterba
parent 8e7e9c672f
commit b086c5bd99
1 changed files with 19 additions and 2 deletions
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21
fs/btrfs/subpage.c
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@ -328,24 +328,34 @@ static void btrfs_subpage_start_writer(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;
int ret;
btrfs_subpage_assert(fs_info, folio, start, len);
spin_lock_irqsave(&subpage->lock, flags);
ASSERT(atomic_read(&subpage->readers) == 0);
ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
bitmap_set(subpage->bitmaps, start_bit, nbits);
ret = atomic_add_return(nbits, &subpage->writers);
ASSERT(ret == nbits);
spin_unlock_irqrestore(&subpage->lock, flags);
}
static bool btrfs_subpage_end_and_test_writer(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 last;
btrfs_subpage_assert(fs_info, folio, start, len);
spin_lock_irqsave(&subpage->lock, flags);
/*
* We have call sites passing @lock_page into
* extent_clear_unlock_delalloc() for compression path.
@ -353,11 +363,18 @@ static bool btrfs_subpage_end_and_test_writer(const struct btrfs_fs_info *fs_inf
* This @locked_page is locked by plain lock_page(), thus its
* subpage::writers is 0. Handle them in a special way.
*/
if (atomic_read(&subpage->writers) == 0)
if (atomic_read(&subpage->writers) == 0) {
spin_unlock_irqrestore(&subpage->lock, flags);
return true;
}
ASSERT(atomic_read(&subpage->writers) >= nbits);
return atomic_sub_and_test(nbits, &subpage->writers);
/* The target range should have been locked. */
ASSERT(bitmap_test_range_all_set(subpage->bitmaps, start_bit, nbits));
bitmap_clear(subpage->bitmaps, start_bit, nbits);
last = atomic_sub_and_test(nbits, &subpage->writers);
spin_unlock_irqrestore(&subpage->lock, flags);
return last;
}
/*