From 0852b6ca941ef3ff75076e85738877bd3271e1cd Mon Sep 17 00:00:00 2001 From: Gao Xiang Date: Mon, 10 May 2021 14:47:15 +0800 Subject: [PATCH] erofs: fix 1 lcluster-sized pcluster for big pcluster If the 1st NONHEAD lcluster of a pcluster isn't CBLKCNT lcluster type rather than a HEAD or PLAIN type instead, which means its pclustersize _must_ be 1 lcluster (since its uncompressed size < 2 lclusters), as illustrated below: HEAD HEAD / PLAIN lcluster type ____________ ____________ |_:__________|_________:__| file data (uncompressed) . . .____________. |____________| pcluster data (compressed) Such on-disk case was explained before [1] but missed to be handled properly in the runtime implementation. It can be observed if manually generating 1 lcluster-sized pcluster with 2 lclusters (thus CBLKCNT doesn't exist.) Let's fix it now. [1] https://lore.kernel.org/r/20210407043927.10623-1-xiang@kernel.org Link: https://lore.kernel.org/r/20210510064715.29123-1-xiang@kernel.org Fixes: cec6e93beadf ("erofs: support parsing big pcluster compress indexes") Reviewed-by: Chao Yu Signed-off-by: Gao Xiang --- fs/erofs/zmap.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-) diff --git a/fs/erofs/zmap.c b/fs/erofs/zmap.c index e62d813756f2..efaf32596b97 100644 --- a/fs/erofs/zmap.c +++ b/fs/erofs/zmap.c @@ -450,14 +450,31 @@ static int z_erofs_get_extent_compressedlen(struct z_erofs_maprecorder *m, lcn = m->lcn + 1; if (m->compressedlcs) goto out; - if (lcn == initial_lcn) - goto err_bonus_cblkcnt; err = z_erofs_load_cluster_from_disk(m, lcn); if (err) return err; + /* + * If the 1st NONHEAD lcluster has already been handled initially w/o + * valid compressedlcs, which means at least it mustn't be CBLKCNT, or + * an internal implemenatation error is detected. + * + * The following code can also handle it properly anyway, but let's + * BUG_ON in the debugging mode only for developers to notice that. + */ + DBG_BUGON(lcn == initial_lcn && + m->type == Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD); + switch (m->type) { + case Z_EROFS_VLE_CLUSTER_TYPE_PLAIN: + case Z_EROFS_VLE_CLUSTER_TYPE_HEAD: + /* + * if the 1st NONHEAD lcluster is actually PLAIN or HEAD type + * rather than CBLKCNT, it's a 1 lcluster-sized pcluster. + */ + m->compressedlcs = 1; + break; case Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD: if (m->delta[0] != 1) goto err_bonus_cblkcnt;