[v4,07/10] btrfs: subpage: dump the involved bitmap when ASSERT() failed

Commit Message

Qu Wenruo Jan. 11, 2025, 10:43 a.m. UTC

For btrfs_folio_assert_not_dirty() and btrfs_folio_set_lock(), we call
bitmap_test_range_all_zero() to ensure the involved range has no
dirty/lock bit already set.

However with my recent enhanced delalloc range error handling, I was
hitting the ASSERT() inside btrfs_folio_set_lock(), and it turns out
that some error handling path is not properly update the folio flags.

So add some extra dumpping for the ASSERTs to dump the involved bitmap
to help debug.

Reviewed-by: Boris Burkov <[e-mail]>
Signed-off-by: Qu Wenruo <[e-mail]>
---
 fs/btrfs/subpage.c | 41 ++++++++++++++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 11 deletions(-)

Patch

diff --git a/fs/btrfs/subpage.c b/fs/btrfs/subpage.c
index 03d7bfc042e2..5d088f7d6184 100644
--- a/fs/btrfs/subpage.c
+++ b/fs/btrfs/subpage.c
@@ -635,6 +635,28 @@  IMPLEMENT_BTRFS_PAGE_OPS(ordered, folio_set_ordered, folio_clear_ordered,
 IMPLEMENT_BTRFS_PAGE_OPS(checked, folio_set_checked, folio_clear_checked,
 			 folio_test_checked);
 
+#define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst)			\
+{									\
+	const int sectors_per_page = fs_info->sectors_per_page;		\
+									\
+	ASSERT(sectors_per_page < BITS_PER_LONG);			\
+	*dst = bitmap_read(subpage->bitmaps,				\
+			   sectors_per_page * btrfs_bitmap_nr_##name,	\
+			   sectors_per_page);				\
+}
+
+#define subpage_dump_bitmap(fs_info, folio, name, start, len)		\
+{									\
+	struct btrfs_subpage *subpage = folio_get_private(folio);	\
+	unsigned long bitmap;						\
+									\
+	GET_SUBPAGE_BITMAP(subpage, fs_info, name, &bitmap);		\
+	btrfs_warn(fs_info,						\
+	"dumpping bitmap start=%llu len=%u folio=%llu " #name "_bitmap=%*pbl", \
+		   start, len, folio_pos(folio),			\
+		   fs_info->sectors_per_page, &bitmap);			\
+}
+
 /*
  * Make sure not only the page dirty bit is cleared, but also subpage dirty bit
  * is cleared.
@@ -660,6 +682,10 @@  void btrfs_folio_assert_not_dirty(const struct btrfs_fs_info *fs_info,
 	subpage = folio_get_private(folio);
 	ASSERT(subpage);
 	spin_lock_irqsave(&subpage->lock, flags);
+	if (unlikely(!bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits))) {
+		subpage_dump_bitmap(fs_info, folio, dirty, start, len);
+		ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
+	}
 	ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
@@ -689,23 +715,16 @@  void btrfs_folio_set_lock(const struct btrfs_fs_info *fs_info,
 	nbits = len >> fs_info->sectorsize_bits;
 	spin_lock_irqsave(&subpage->lock, flags);
 	/* Target range should not yet be locked. */
-	ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
+	if (unlikely(!bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits))) {
+		subpage_dump_bitmap(fs_info, folio, locked, start, len);
+		ASSERT(bitmap_test_range_all_zero(subpage->bitmaps, start_bit, nbits));
+	}
 	bitmap_set(subpage->bitmaps, start_bit, nbits);
 	ret = atomic_add_return(nbits, &subpage->nr_locked);
 	ASSERT(ret <= fs_info->sectors_per_page);
 	spin_unlock_irqrestore(&subpage->lock, flags);
 }
 
-#define GET_SUBPAGE_BITMAP(subpage, fs_info, name, dst)			\
-{									\
-	const int sectors_per_page = fs_info->sectors_per_page;		\
-									\
-	ASSERT(sectors_per_page < BITS_PER_LONG);			\
-	*dst = bitmap_read(subpage->bitmaps,				\
-			   sectors_per_page * btrfs_bitmap_nr_##name,	\
-			   sectors_per_page);				\
-}
-
 void __cold btrfs_subpage_dump_bitmap(const struct btrfs_fs_info *fs_info,
 				      struct folio *folio, u64 start, u32 len)
 {