erofs: ensure all folios are managed in erofs_try_to_free_all_cached_folios()

[PATCH] [PATCH v3] erofs: ensure all folios are managed in erofs_try_to_free_all_cached_folios()

Posted by Zhan Xusheng 1 day, 6 hours ago

folio_trylock() in erofs_try_to_free_all_cached_folios() may
successfully acquire the folio lock, but the subsequent check
for erofs_folio_is_managed() can skip unlocking when the folio
is not managed by EROFS.

As Gao Xiang pointed out, this condition should not happen in
practice because compressed_bvecs[] only holds valid cached folios
at this point — any non-managed folio would have already been
detached by z_erofs_cache_release_folio() under folio lock.

Fix this by adding DBG_BUGON() to catch unexpected folios
and ensure folio_unlock() is always called.

Suggested-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>
---
 fs/erofs/zdata.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index fe8121df9ef2..b566996a0d1a 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -605,8 +605,7 @@ static int erofs_try_to_free_all_cached_folios(struct erofs_sb_info *sbi,
 			if (!folio_trylock(folio))
 				return -EBUSY;
 
-			if (!erofs_folio_is_managed(sbi, folio))
-				continue;
+			DBG_BUGON(!erofs_folio_is_managed(sbi, folio));
 			pcl->compressed_bvecs[i].page = NULL;
 			folio_detach_private(folio);
 			folio_unlock(folio);
-- 
2.43.0

Re: [PATCH] [PATCH v3] erofs: ensure all folios are managed in erofs_try_to_free_all_cached_folios()

Posted by Gao Xiang 1 day, 5 hours ago


On 2026/3/31 13:02, Zhan Xusheng wrote:
> folio_trylock() in erofs_try_to_free_all_cached_folios() may
> successfully acquire the folio lock, but the subsequent check
> for erofs_folio_is_managed() can skip unlocking when the folio
> is not managed by EROFS.
> 
> As Gao Xiang pointed out, this condition should not happen in
> practice because compressed_bvecs[] only holds valid cached folios
> at this point — any non-managed folio would have already been
> detached by z_erofs_cache_release_folio() under folio lock.
> 
> Fix this by adding DBG_BUGON() to catch unexpected folios
> and ensure folio_unlock() is always called.
> 
> Suggested-by: Gao Xiang <hsiangkao@linux.alibaba.com>
> Signed-off-by: Zhan Xusheng <zhanxusheng@xiaomi.com>

Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>

Thanks,
Gao Xiang