AcoSail/kernel_optimize_test
8
0
Fork 0
forked from luck/tmp_suning_uos_patched
Code Pull Requests Activity

swap: fix do_swap_page() race with swapoff

Browse Source 
[ Upstream commit 2799e77529c2a25492a4395db93996e3dacd762d ]

When I was investigating the swap code, I found the below possible race
window:

CPU 1                                   	CPU 2
-----                                   	-----
do_swap_page
  if (data_race(si->flags & SWP_SYNCHRONOUS_IO)
  swap_readpage
    if (data_race(sis->flags & SWP_FS_OPS)) {
                                        	swapoff
					  	  ..
					  	  p->swap_file = NULL;
					  	  ..
    struct file *swap_file = sis->swap_file;
    struct address_space *mapping = swap_file->f_mapping;[oops!]

Note that for the pages that are swapped in through swap cache, this isn't
an issue. Because the page is locked, and the swap entry will be marked
with SWAP_HAS_CACHE, so swapoff() can not proceed until the page has been
unlocked.

Fix this race by using get/put_swap_device() to guard against concurrent
swapoff.

Link: https://lkml.kernel.org/r/20210426123316.806267-3-linmiaohe@huawei.com
Fixes: 0bcac06f27 ("mm,swap: skip swapcache for swapin of synchronous device")
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: "Huang, Ying" <ying.huang@intel.com>
Cc: Alex Shi <alexs@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Wei Yang <richard.weiyang@gmail.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Miaohe Lin 2021-06-28 19:36:50 -07:00 committed by Greg Kroah-Hartman
parent 29ae2c9c9c
commit a5dcdfe4cb
2 changed files with 18 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
include/linux/swap.h
View File

@ -503,6 +503,15 @@ static inline struct swap_info_struct *swp_swap_info(swp_entry_t entry)
return NULL;
}
static inline struct swap_info_struct *get_swap_device(swp_entry_t entry)
{
return NULL;
}
static inline void put_swap_device(struct swap_info_struct *si)
{
}
#define swap_address_space(entry) (NULL)
#define get_nr_swap_pages() 0L
#define total_swap_pages 0L

11
mm/memory.c
View File

@ -3302,6 +3302,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
{
struct vm_area_struct *vma = vmf->vma;
struct page *page = NULL, *swapcache;
struct swap_info_struct *si = NULL;
swp_entry_t entry;
pte_t pte;
int locked;
@ -3329,14 +3330,16 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
goto out;
}
/* Prevent swapoff from happening to us. */
si = get_swap_device(entry);
if (unlikely(!si))
goto out;
delayacct_set_flag(DELAYACCT_PF_SWAPIN);
page = lookup_swap_cache(entry, vma, vmf->address);
swapcache = page;
if (!page) {
struct swap_info_struct *si = swp_swap_info(entry);
if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
__swap_count(entry) == 1) {
/* skip swapcache */
@ -3507,6 +3510,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
unlock:
pte_unmap_unlock(vmf->pte, vmf->ptl);
out:
if (si)
put_swap_device(si);
return ret;
out_nomap:
pte_unmap_unlock(vmf->pte, vmf->ptl);
@ -3518,6 +3523,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
unlock_page(swapcache);
put_page(swapcache);
}
if (si)
put_swap_device(si);
return ret;
}