On 2025/5/6 18:18, Gao Xiang wrote:
When compressed data deduplication is enabled, multiple logical extents may reference the same compressed physical cluster. The previous commit 94c43de73521 ("erofs: fix wrong primary bvec selection on deduplicated extents") already avoids using shortened bvecs. However, in such cases, the extra temporary buffers also need to be preserved for later use in z_erofs_fill_other_copies() to to prevent data corruption. IOWs, extra temporary buffers have to be retained not only due to varying start relative offsets (`pageofs_out`, as indicated by `pcl->multibases`) but also because of shortened bvecs. android.hardware.graphics.compo...@2.1.so : 270696 bytes 0: 0.. 204185 | 204185 : 628019200.. 628084736 | 65536 -> 1: 204185.. 225536 | 21351 : 544063488.. 544129024 | 65536 2: 225536.. 270696 | 45160 : 0.. 0 | 0 com.android.vndk.v28.apex : 93814897 bytes ... 364: 53869896..54095257 | 225361 : 543997952.. 544063488 | 65536 -> 365: 54095257..54309344 | 214087 : 544063488.. 544129024 | 65536 366: 54309344..54514557 | 205213 : 544129024.. 544194560 | 65536 ... Both 204185 and 54095257 have the same start relative offset of 3481, but the logical page 55 of `android.hardware.graphics.compo...@2.1.so` ranges from 225280 to 229632, forming a shortened bvec [225280, 225536) that cannot be used for decompressing the range from 54095257 to 54309344 of `com.android.vndk.v28.apex`. Since `pcl->multibases` is already meaningless, just mark `keepxcpy` on demand for simplicity. Again, this issue can only lead to data corruption if `-Ededupe` is on. Fixes: 94c43de73521 ("erofs: fix wrong primary bvec selection on deduplicated extents") Signed-off-by: Gao Xiang <hsiang...@linux.alibaba.com> --- fs/erofs/zdata.c | 31 ++++++++++++++----------------- 1 file changed, 14 insertions(+), 17 deletions(-) diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c index 5c061aaeeb45..b8e6b76c23d5 100644 --- a/fs/erofs/zdata.c +++ b/fs/erofs/zdata.c @@ -79,9 +79,6 @@ struct z_erofs_pcluster { /* L: whether partial decompression or not */ bool partial;- /* L: indicate several pageofs_outs or not */- bool multibases; - /* L: whether extra buffer allocations are best-effort */ bool besteffort;@@ -1046,8 +1043,6 @@ static int z_erofs_scan_folio(struct z_erofs_frontend *f,break;erofs_onlinefolio_split(folio);- if (f->pcl->pageofs_out != (map->m_la & ~PAGE_MASK)) - f->pcl->multibases = true; if (f->pcl->length < offset + end - map->m_la) { f->pcl->length = offset + end - map->m_la; f->pcl->pageofs_out = map->m_la & ~PAGE_MASK; @@ -1093,7 +1088,6 @@ struct z_erofs_backend { struct page *onstack_pages[Z_EROFS_ONSTACK_PAGES]; struct super_block *sb; struct z_erofs_pcluster *pcl; - /* pages with the longest decompressed length for deduplication */ struct page **decompressed_pages; /* pages to keep the compressed data */ @@ -1102,6 +1096,8 @@ struct z_erofs_backend { struct list_head decompressed_secondary_bvecs; struct page **pagepool; unsigned int onstack_used, nr_pages; + /* indicate if temporary copies should be preserved for later use */ + bool keepxcpy; };struct z_erofs_bvec_item {@@ -1112,18 +1108,20 @@ struct z_erofs_bvec_item { static void z_erofs_do_decompressed_bvec(struct z_erofs_backend *be, struct z_erofs_bvec *bvec) { + int poff = bvec->offset + be->pcl->pageofs_out;
Looks good! Reviewed-by: Hongbo Li <lihongb...@huawei.com> Thanks, Hongbo
struct z_erofs_bvec_item *item; - unsigned int pgnr; - - if (!((bvec->offset + be->pcl->pageofs_out) & ~PAGE_MASK) && - (bvec->end == PAGE_SIZE || - bvec->offset + bvec->end == be->pcl->length)) { - pgnr = (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT; - DBG_BUGON(pgnr >= be->nr_pages); - if (!be->decompressed_pages[pgnr]) { - be->decompressed_pages[pgnr] = bvec->page; + struct page **page; + + if (!(poff & ~PAGE_MASK) && (bvec->end == PAGE_SIZE || + bvec->offset + bvec->end == be->pcl->length)) { + DBG_BUGON((poff >> PAGE_SHIFT) >= be->nr_pages); + page = be->decompressed_pages + (poff >> PAGE_SHIFT); + if (!*page) { + *page = bvec->page; return; } + } else { + be->keepxcpy = true; }/* (cold path) one pcluster is requested multiple times */@@ -1289,7 +1287,7 @@ static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, int err) .alg = pcl->algorithmformat, .inplace_io = overlapped, .partial_decoding = pcl->partial, - .fillgaps = pcl->multibases, + .fillgaps = be->keepxcpy, .gfp = pcl->besteffort ? GFP_KERNEL : GFP_NOWAIT | __GFP_NORETRY }, be->pagepool); @@ -1346,7 +1344,6 @@ static int z_erofs_decompress_pcluster(struct z_erofs_backend *be, int err)pcl->length = 0;pcl->partial = true; - pcl->multibases = false; pcl->besteffort = false; pcl->bvset.nextpage = NULL; pcl->vcnt = 0;
