erofs: shouldn't churn the mapping page for duplicated copies

If other duplicated copies exist in one decompression shot, should
leave the old page as is rather than replace it with the new duplicated
one.  Otherwise, the following cold path to deal with duplicated copies
will use the invalid bvec.  It impacts compressed data deduplication.

Also, shift the onlinepage EIO bit to avoid touching the signed bit.

Fixes: 267f2492c8f7 ("erofs: introduce multi-reference pclusters (fully-referenced)")
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20221012045056.13421-1-hsiangkao@linux.alibaba.com

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 559380a535afffda7735fdb80ac09aebc130d8e1..4553be650968b641e1c46d1405ff3c7b6abc5a10 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -888,15 +888,13 @@ static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_backend *be,
 
        if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK)) {
                unsigned int pgnr;
-               struct page *oldpage;
 
                pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;
                DBG_BUGON(pgnr >= be->nr_pages);
-               oldpage = be->decompressed_pages[pgnr];
-               be->decompressed_pages[pgnr] = bvec->page;
-
-               if (!oldpage)
+               if (!be->decompressed_pages[pgnr]) {
+                       be->decompressed_pages[pgnr] = bvec->page;
                        return;
+               }
        }
 
        /* (cold path) one pcluster is requested multiple times */

diff --git a/fs/erofs/zdata.h b/fs/erofs/zdata.h
index e7f04c4fbb81c5742915f5120d5e198efce62218..d98c952129852a95759cfca43e2b0ac3340f3fe6 100644 (file)
--- a/fs/erofs/zdata.h
+++ b/fs/erofs/zdata.h
@@ -126,10 +126,10 @@ static inline unsigned int z_erofs_pclusterpages(struct z_erofs_pcluster *pcl)
 }
 
 /*
- * bit 31: I/O error occurred on this page
- * bit 0 - 30: remaining parts to complete this page
+ * bit 30: I/O error occurred on this page
+ * bit 0 - 29: remaining parts to complete this page
  */
-#define Z_EROFS_PAGE_EIO                       (1 << 31)
+#define Z_EROFS_PAGE_EIO                       (1 << 30)
 
 static inline void z_erofs_onlinepage_init(struct page *page)
 {