This is a note to let you know that I've just added the patch titled
btrfs: unify to use writer locks for subpage locking
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
btrfs-unify-to-use-writer-locks-for-subpage-locking.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 53439df281508c3c819e6fd8f7f14fb84d93b2f8
Author: Qu Wenruo <wqu@xxxxxxxx>
Date: Wed Oct 9 16:21:06 2024 +1030
btrfs: unify to use writer locks for subpage locking
[ Upstream commit 336e69f3025fb70db9d0dfb7f36ac79887bf5341 ]
Since commit d7172f52e993 ("btrfs: use per-buffer locking for
extent_buffer reading"), metadata read no longer relies on the subpage
reader locking.
This means we do not need to maintain a different metadata/data split
for locking, so we can convert the existing reader lock users by:
- add_ra_bio_pages()
Convert to btrfs_folio_set_writer_lock()
- end_folio_read()
Convert to btrfs_folio_end_writer_lock()
- begin_folio_read()
Convert to btrfs_folio_set_writer_lock()
- folio_range_has_eb()
Remove the subpage->readers checks, since it is always 0.
- Remove btrfs_subpage_start_reader() and btrfs_subpage_end_reader()
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Reviewed-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Stable-dep-of: 8bf334beb349 ("btrfs: fix double accounting race when extent_writepage_io() failed")
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 90aef2627ca27..64eaf74fbebc8 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -545,8 +545,7 @@ static noinline int add_ra_bio_pages(struct inode *inode,
* subpage::readers and to unlock the page.
*/
if (fs_info->sectorsize < PAGE_SIZE)
- btrfs_subpage_start_reader(fs_info, folio, cur,
- add_size);
+ btrfs_folio_set_writer_lock(fs_info, folio, cur, add_size);
folio_put(folio);
cur += add_size;
}
diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 8222ae6f29af5..5d6b3b812593d 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -438,7 +438,7 @@ static void end_folio_read(struct folio *folio, bool uptodate, u64 start, u32 le
if (!btrfs_is_subpage(fs_info, folio->mapping))
folio_unlock(folio);
else
- btrfs_subpage_end_reader(fs_info, folio, start, len);
+ btrfs_folio_end_writer_lock(fs_info, folio, start, len);
}
/*
@@ -495,7 +495,7 @@ static void begin_folio_read(struct btrfs_fs_info *fs_info, struct folio *folio)
return;
ASSERT(folio_test_private(folio));
- btrfs_subpage_start_reader(fs_info, folio, folio_pos(folio), PAGE_SIZE);
+ btrfs_folio_set_writer_lock(fs_info, folio, folio_pos(folio), PAGE_SIZE);
}
/*
@@ -2507,12 +2507,6 @@ static bool folio_range_has_eb(struct btrfs_fs_info *fs_info, struct folio *foli
subpage = folio_get_private(folio);
if (atomic_read(&subpage->eb_refs))
return true;
- /*
- * Even there is no eb refs here, we may still have
- * end_folio_read() call relying on page::private.
- */
- if (atomic_read(&subpage->readers))
- return true;
}
return false;
}
diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 99341e98bbcc7..0587a7d7b5e81 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -140,12 +140,10 @@ struct btrfs_subpage *btrfs_alloc_subpage(const struct btrfs_fs_info *fs_info,
return ERR_PTR(-ENOMEM);
spin_lock_init(&ret->lock);
- if (type == BTRFS_SUBPAGE_METADATA) {
+ if (type == BTRFS_SUBPAGE_METADATA)
atomic_set(&ret->eb_refs, 0);
- } else {
- atomic_set(&ret->readers, 0);
+ else
atomic_set(&ret->writers, 0);
- }
return ret;
}
@@ -221,62 +219,6 @@ static void btrfs_subpage_assert(const struct btrfs_fs_info *fs_info,
__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(BTRFS_I(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);
-
- /*
- * For data we need to unlock the page if the last read has finished.
- *
- * And please don't replace @last with atomic_sub_and_test() call
- * inside if () condition.
- * As we want the atomic_sub_and_test() to be always executed.
- */
- 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)
{
u64 orig_start = *start;
diff --git a/fs/btrfs/subpage.h b/fs/btrfs/subpage.h
index 6289d6f65b87d..8488ea057b30b 100644
--- a/fs/btrfs/subpage.h
+++ b/fs/btrfs/subpage.h
@@ -45,14 +45,6 @@ enum {
struct btrfs_subpage {
/* Common members for both data and metadata pages */
spinlock_t lock;
- /*
- * Both data and metadata needs to track how many readers are for the
- * page.
- * Data relies on @readers to unlock the page when last reader finished.
- * While metadata doesn't need page unlock, it needs to prevent
- * page::private get cleared before the last end_page_read().
- */
- atomic_t readers;
union {
/*
* Structures only used by metadata
@@ -95,11 +87,6 @@ void btrfs_free_subpage(struct btrfs_subpage *subpage);
void btrfs_folio_inc_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
void btrfs_folio_dec_eb_refs(const struct btrfs_fs_info *fs_info, struct folio *folio);
-void btrfs_subpage_start_reader(const struct btrfs_fs_info *fs_info,
- struct folio *folio, u64 start, u32 len);
-void btrfs_subpage_end_reader(const struct btrfs_fs_info *fs_info,
- struct folio *folio, u64 start, u32 len);
-
void btrfs_folio_end_writer_lock(const struct btrfs_fs_info *fs_info,
struct folio *folio, u64 start, u32 len);
void btrfs_folio_set_writer_lock(const struct btrfs_fs_info *fs_info,
