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| author |   Henry Burns <henryburns@google.com> | 2019-08-24 17:55:03 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2019-08-24 19:48:42 -0700 |
| commit | 1a87aa03597efa9641e92875b883c94c7f872ccb (patch) | |
| tree | 103f56f4522e007ab19b70094b5463a5062963e0 /mm | |
| parent | mm, page_owner: handle THP splits correctly (diff) | |
| download | linux-dev-1a87aa03597efa9641e92875b883c94c7f872ccb.tar.xz linux-dev-1a87aa03597efa9641e92875b883c94c7f872ccb.zip | |
mm/zsmalloc.c: migration can leave pages in ZS_EMPTY indefinitely
In zs_page_migrate() we call putback_zspage() after we have finished
migrating all pages in this zspage. However, the return value is
ignored. If a zs_free() races in between zs_page_isolate() and
zs_page_migrate(), freeing the last object in the zspage,
putback_zspage() will leave the page in ZS_EMPTY for potentially an
unbounded amount of time.
To fix this, we need to do the same thing as zs_page_putback() does:
schedule free_work to occur.
To avoid duplicated code, move the sequence to a new
putback_zspage_deferred() function which both zs_page_migrate() and
zs_page_putback() call.
Link: http://lkml.kernel.org/r/20190809181751.219326-1-henryburns@google.com
Fixes: 48b4800a1c6a ("zsmalloc: page migration support")
Signed-off-by: Henry Burns <henryburns@google.com>
Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Henry Burns <henrywolfeburns@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Jonathan Adams <jwadams@google.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/zsmalloc.c | 19 |
1 files changed, 15 insertions, 4 deletions
diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index 57fbb7ced69f..5105b9b66653 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1862,6 +1862,18 @@ static void dec_zspage_isolation(struct zspage *zspage) zspage->isolated--; } +static void putback_zspage_deferred(struct zs_pool *pool, + struct size_class *class, + struct zspage *zspage) +{ + enum fullness_group fg; + + fg = putback_zspage(class, zspage); + if (fg == ZS_EMPTY) + schedule_work(&pool->free_work); + +} + static void replace_sub_page(struct size_class *class, struct zspage *zspage, struct page *newpage, struct page *oldpage) { @@ -2031,7 +2043,7 @@ static int zs_page_migrate(struct address_space *mapping, struct page *newpage, * the list if @page is final isolated subpage in the zspage. */ if (!is_zspage_isolated(zspage)) - putback_zspage(class, zspage); + putback_zspage_deferred(pool, class, zspage); reset_page(page); put_page(page); @@ -2077,14 +2089,13 @@ static void zs_page_putback(struct page *page) spin_lock(&class->lock); dec_zspage_isolation(zspage); if (!is_zspage_isolated(zspage)) { - fg = putback_zspage(class, zspage); /* * Due to page_lock, we cannot free zspage immediately * so let's defer. */ - if (fg == ZS_EMPTY) - schedule_work(&pool->free_work); + putback_zspage_deferred(pool, class, zspage); } + spin_unlock(&class->lock); } |