The patch titled
Subject: filemap: check compound_head(page)->mapping in filemap_fault()
has been added to the -mm tree. Its filename is
filemap-check-compound_headpage-mapping-in-filemap_fault.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/filemap-check-compound_headpage-mapping-in-filemap_fault.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/filemap-check-compound_headpage-mapping-in-filemap_fault.patch
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------------------------------------------------------
From: Song Liu <songliubraving@xxxxxx>
Subject: filemap: check compound_head(page)->mapping in filemap_fault()
Patch series "Enable THP for text section of non-shmem files", v10;
This patchset follows up discussion at LSF/MM 2019. The motivation is to
put text section of an application in THP, and thus reduces iTLB miss rate
and improves performance. Both Facebook and Oracle showed strong
interests to this feature.
To make reviews easier, this set aims a mininal valid product. Current
version of the work does not have any changes to file system specific
code. This comes with some limitations (discussed later).
This set enables an application to "hugify" its text section by simply
running something like:
madvise(0x600000, 0x80000, MADV_HUGEPAGE);
Before this call, the /proc/<pid>/maps looks like:
00400000-074d0000 r-xp 00000000 00:27 2006927 app
After this call, part of the text section is split out and mapped to
THP:
00400000-00425000 r-xp 00000000 00:27 2006927 app
00600000-00e00000 r-xp 00200000 00:27 2006927 app <<< on THP
00e00000-074d0000 r-xp 00a00000 00:27 2006927 app
Limitations:
1. This only works for text section (vma with VM_DENYWRITE).
2. Original limitation #2 is removed in v3.
We gated this feature with an experimental config, READ_ONLY_THP_FOR_FS.
Once we get better support on the write path, we can remove the config and
enable it by default.
Tested cases:
1. Tested with btrfs and ext4.
2. Tested with real work application (memcache like caching service).
3. Tested with "THP aware uprobe":
https://patchwork.kernel.org/project/linux-mm/list/?series=131339
This patch (of 7):
Currently, filemap_fault() avoids race condition with truncate by checking
page->mapping == mapping. This does not work for compound pages. This
patch let it check compound_head(page)->mapping instead.
Link: http://lkml.kernel.org/r/20190801184244.3169074-2-songliubraving@xxxxxx
Signed-off-by: Song Liu <songliubraving@xxxxxx>
Acked-by: Rik van Riel <riel@xxxxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/filemap.c~filemap-check-compound_headpage-mapping-in-filemap_fault
+++ a/mm/filemap.c
@@ -2541,7 +2541,7 @@ retry_find:
goto out_retry;
/* Did it get truncated? */
- if (unlikely(page->mapping != mapping)) {
+ if (unlikely(compound_head(page)->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto retry_find;
_
Patches currently in -mm which might be from songliubraving@xxxxxx are
mm-move-memcmp_pages-and-pages_identical.patch
uprobe-use-original-page-when-all-uprobes-are-removed.patch
uprobe-use-original-page-when-all-uprobes-are-removed-v2.patch
mm-thp-introduce-foll_split_pmd.patch
mm-thp-introduce-foll_split_pmd-v11.patch
uprobe-use-foll_split_pmd-instead-of-foll_split.patch
khugepaged-enable-collapse-pmd-for-pte-mapped-thp.patch
uprobe-collapse-thp-pmd-after-removing-all-uprobes.patch
filemap-check-compound_headpage-mapping-in-filemap_fault.patch
filemap-check-compound_headpage-mapping-in-pagecache_get_page.patch
filemap-update-offset-check-in-filemap_fault.patch
mmthp-stats-for-file-backed-thp.patch
khugepaged-rename-collapse_shmem-and-khugepaged_scan_shmem.patch
mmthp-add-read-only-thp-support-for-non-shmem-fs.patch
mmthp-avoid-writes-to-file-with-thp-in-pagecache.patch
