erofs: avoid useless loops in z_erofs_pcluster_readmore() when reading beyond EOF

z_erofs_pcluster_readmore() may take a long time to loop when the page
offset is large enough, which is unnecessary should be prevented.

For example, when the following case is encountered, it will loop 4691368
times, taking about 27 seconds:
    - offset = 19217289215
    - inode_size = 1442672

Signed-off-by: Chunhai Guo <guochunhai@vivo.com>
Fixes: 386292919c25 ("erofs: introduce readmore decompression strategy")
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230710042531.28761-1-guochunhai@vivo.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 5f1890e309c6ebaeebc4672a1665a4ec65043a53..d9a0763f459570eecf91dd2dcbd8e2b1bd1f6417 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1841,7 +1841,7 @@ static void z_erofs_pcluster_readmore(struct z_erofs_decompress_frontend *f,
        }
 
        cur = map->m_la + map->m_llen - 1;
-       while (cur >= end) {
+       while ((cur >= end) && (cur < i_size_read(inode))) {
                pgoff_t index = cur >> PAGE_SHIFT;
                struct page *page;