Commit f68c34ca authored May 10, 2021 by Gao Xiang Committed by Gao Xiang Apr 08, 2022

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 <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <xiang@kernel.org>

parent 50ea9ae0

fs/erofs/zmap.c

+19 −2

Original line number	Diff line number	Diff line
		@@ -449,14 +449,31 @@ 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;