Currently, there are two kinds of compressed pages in erofs:
1) file pages for the in-place decompression and
2) managed pages for cached decompression.
Both are all stored in grp->compressed_pages[].
For managed pages, they could already exist or could be preloaded
in this round, including the following cases in detail:
1) Already valid (loaded in some previous round);
2) PAGE_UNALLOCATED, should be allocated at the time of submission;
3) Just found in the managed cache, and with an extra page ref.
Currently, 1) and 3) can be distinguishable by lock_page and
checking its PG_private, which is guaranteed by the reclaim path,
but it's better to do a double check by using an extra tag.
This patch reworks the preload flow by introducing such the tag
by using tagged pointer, too many #ifdefs are removed as well.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
92e6efd566