Commit 7c3ca183 authored by Gao Xiang's avatar Gao Xiang
Browse files

erofs: restrict pcluster size limitations 



Error out if {en,de}encoded size of a pcluster is unsupported:
  Maximum supported encoded size (of a pcluster):  1 MiB
  Maximum supported decoded size (of a pcluster): 12 MiB

Users can still choose to use supported large configurations (e.g.,
for archival purposes), but there may be performance penalties in
low-memory scenarios compared to smaller pclusters.

Reviewed-by: default avatarChao Yu <chao@kernel.org>
Signed-off-by: default avatarGao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240912074156.2925394-1-hsiangkao@linux.alibaba.com
parent 79f504a2

fs/erofs/erofs_fs.h

+4 −1
Original line number Diff line number Diff line
@@ -288,9 +288,12 @@ struct erofs_dirent { 


#define EROFS_NAME_LEN      255



/* maximum supported size of a physical compression cluster */

/* maximum supported encoded size of a physical compressed cluster */

#define Z_EROFS_PCLUSTER_MAX_SIZE	(1024 * 1024)



/* maximum supported decoded size of a physical compressed cluster */

#define Z_EROFS_PCLUSTER_MAX_DSIZE	(12 * 1024 * 1024)



/* available compression algorithm types (for h_algorithmtype) */

enum {

	Z_EROFS_COMPRESSION_LZ4		= 0,

fs/erofs/zmap.c

+20 −22
Original line number Diff line number Diff line
@@ -687,32 +687,30 @@ int z_erofs_map_blocks_iter(struct inode *inode, struct erofs_map_blocks *map, 
	int err = 0;



	trace_erofs_map_blocks_enter(inode, map, flags);



	/* when trying to read beyond EOF, leave it unmapped */

	if (map->m_la >= inode->i_size) {

	if (map->m_la >= inode->i_size) {	/* post-EOF unmapped extent */

		map->m_llen = map->m_la + 1 - inode->i_size;

		map->m_la = inode->i_size;

		map->m_flags = 0;

		goto out;

	}



	} else {

		err = z_erofs_fill_inode_lazy(inode);

	if (err)

		goto out;



		if (!err) {

			if ((vi->z_advise & Z_EROFS_ADVISE_FRAGMENT_PCLUSTER) &&

			    !vi->z_tailextent_headlcn) {

				map->m_la = 0;

				map->m_llen = inode->i_size;

		map->m_flags = EROFS_MAP_MAPPED | EROFS_MAP_FULL_MAPPED |

				EROFS_MAP_FRAGMENT;

		goto out;

	}



				map->m_flags = EROFS_MAP_MAPPED |

					EROFS_MAP_FULL_MAPPED | EROFS_MAP_FRAGMENT;

			} else {

				err = z_erofs_do_map_blocks(inode, map, flags);

out:

			}

		}

		if (!err && (map->m_flags & EROFS_MAP_ENCODED) &&

		    unlikely(map->m_plen > Z_EROFS_PCLUSTER_MAX_SIZE ||

			     map->m_llen > Z_EROFS_PCLUSTER_MAX_DSIZE))

			err = -EOPNOTSUPP;

		if (err)

			map->m_llen = 0;

	}

	trace_erofs_map_blocks_exit(inode, map, flags, err);

	return err;

}