erofs: tidy up z_erofs_do_read_page()

 - Fix a typo: spiltted => split;

 - Move !EROFS_MAP_MAPPED and EROFS_MAP_FRAGMENT upwards;

 - Increase `split` in advance to avoid unnecessary repeats.

Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Link: https://lore.kernel.org/r/20230817082813.81180-4-hsiangkao@linux.alibaba.com

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index 9b67991edc7bf7a7c5da2743e7c52a165d23a5d6..6c78566efb92c001dc46c46764dd021708b83e94 100644 (file)
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -981,49 +981,34 @@ static int z_erofs_do_read_page(struct z_erofs_decompress_frontend *fe,
        struct erofs_map_blocks *const map = &fe->map;
        const loff_t offset = page_offset(page);
        bool tight = true, exclusive;
-       unsigned int cur, end, len, spiltted;
+       unsigned int cur, end, len, split;
        int err = 0;
 
-       /* register locked file pages as online pages in pack */
        z_erofs_onlinepage_init(page);
 
-       spiltted = 0;
+       split = 0;
        end = PAGE_SIZE;
 repeat:
-       cur = end - 1;
-
-       if (offset + cur < map->m_la ||
-           offset + cur >= map->m_la + map->m_llen) {
+       if (offset + end - 1 < map->m_la ||
+           offset + end - 1 >= map->m_la + map->m_llen) {
                z_erofs_pcluster_end(fe);
-               map->m_la = offset + cur;
+               map->m_la = offset + end - 1;
                map->m_llen = 0;
                err = z_erofs_map_blocks_iter(inode, map, 0);
                if (err)
                        goto out;
-       } else if (fe->pcl) {
-               goto hitted;
        }
 
-       if ((map->m_flags & EROFS_MAP_MAPPED) &&
-           !(map->m_flags & EROFS_MAP_FRAGMENT)) {
-               err = z_erofs_pcluster_begin(fe);
-               if (err)
-                       goto out;
-       }
-hitted:
-       /*
-        * Ensure the current partial page belongs to this submit chain rather
-        * than other concurrent submit chains or the noio(bypass) chain since
-        * those chains are handled asynchronously thus the page cannot be used
-        * for inplace I/O or bvpage (should be processed in a strict order.)
-        */
-       tight &= (fe->mode > Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE);
+       cur = offset > map->m_la ? 0 : map->m_la - offset;
+       /* bump split parts first to avoid several separate cases */
+       ++split;
 
-       cur = end - min_t(erofs_off_t, offset + end - map->m_la, end);
        if (!(map->m_flags & EROFS_MAP_MAPPED)) {
                zero_user_segment(page, cur, end);
+               tight = false;
                goto next_part;
        }
+
        if (map->m_flags & EROFS_MAP_FRAGMENT) {
                erofs_off_t fpos = offset + cur - map->m_la;
 
@@ -1032,12 +1017,24 @@ hitted:
                                EROFS_I(inode)->z_fragmentoff + fpos);
                if (err)
                        goto out;
-               ++spiltted;
                tight = false;
                goto next_part;
        }
 
-       exclusive = (!cur && (!spiltted || tight));
+       if (!fe->pcl) {
+               err = z_erofs_pcluster_begin(fe);
+               if (err)
+                       goto out;
+       }
+
+       /*
+        * Ensure the current partial page belongs to this submit chain rather
+        * than other concurrent submit chains or the noio(bypass) chain since
+        * those chains are handled asynchronously thus the page cannot be used
+        * for inplace I/O or bvpage (should be processed in a strict order.)
+        */
+       tight &= (fe->mode > Z_EROFS_PCLUSTER_FOLLOWED_NOINPLACE);
+       exclusive = (!cur && ((split <= 1) || tight));
        if (cur)
                tight &= (fe->mode >= Z_EROFS_PCLUSTER_FOLLOWED);
 
@@ -1050,8 +1047,6 @@ hitted:
                goto out;
 
        z_erofs_onlinepage_split(page);
-       /* bump up the number of spiltted parts of a page */
-       ++spiltted;
        if (fe->pcl->pageofs_out != (map->m_la & ~PAGE_MASK))
                fe->pcl->multibases = true;
        if (fe->pcl->length < offset + end - map->m_la) {