Maksytka/linux
1
1
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-12-01 07:26:02 +07:00
Code Issues Packages Projects Releases Wiki Activity

mm, swap: check page poison flag after locking it

Browse Source 
Instead of checking the poison flag only in the fast swap cache lookup
path, always check the poison flags after locking a swap cache folio.

There are two reasons to do so.

The folio is unstable and could be removed from the swap cache anytime, so
it's totally possible that the folio is no longer the backing folio of a
swap entry, and could be an irrelevant poisoned folio.  We might
mistakenly kill a faulting process.

And it's totally possible or even common for the slow swap in path
(swapin_readahead) to bring in a cached folio.  The cache folio could be
poisoned, too.  Only checking the poison flag in the fast path will miss
such folios.

The race window is tiny, so it's very unlikely to happen, though.  While
at it, also add a unlikely prefix.

Link: https://lkml.kernel.org/r/20250916160100.31545-5-ryncsn@gmail.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Acked-by: Chris Li <chrisl@kernel.org>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Nhat Pham <nphamcs@gmail.com>
Suggested-by: Chris Li <chrisl@kernel.org>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <bhe@redhat.com>
Cc: Barry Song <baohua@kernel.org>
Cc: "Huang, Ying" <ying.huang@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: SeongJae Park <sj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Kairui Song
2025-09-17 00:00:49 +08:00
committed by Andrew Morton
parent a733d8de7f
commit 3518b931df
1 changed files with 11 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

22
mm/memory.c
View File

@@ -4661,10 +4661,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
goto out;
folio = swap_cache_get_folio(entry);
if (folio) {
if (folio)
swap_update_readahead(folio, vma, vmf->address);
page = folio_file_page(folio, swp_offset(entry));
}
swapcache = folio;
if (!folio) {
@@ -4735,20 +4733,13 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
ret = VM_FAULT_MAJOR;
count_vm_event(PGMAJFAULT);
count_memcg_event_mm(vma->vm_mm, PGMAJFAULT);
page = folio_file_page(folio, swp_offset(entry));
} else if (PageHWPoison(page)) {
/*
* hwpoisoned dirty swapcache pages are kept for killing
* owner processes (which may be unknown at hwpoison time)
*/
ret = VM_FAULT_HWPOISON;
goto out_release;
}
ret |= folio_lock_or_retry(folio, vmf);
if (ret & VM_FAULT_RETRY)
goto out_release;
page = folio_file_page(folio, swp_offset(entry));
if (swapcache) {
/*
* Make sure folio_free_swap() or swapoff did not release the
@@ -4761,6 +4752,15 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
page_swap_entry(page).val != entry.val))
goto out_page;
if (unlikely(PageHWPoison(page))) {
/*
* hwpoisoned dirty swapcache pages are kept for killing
* owner processes (which may be unknown at hwpoison time)
*/
ret = VM_FAULT_HWPOISON;
goto out_page;
}
/*
* KSM sometimes has to copy on read faults, for example, if
* folio->index of non-ksm folios would be nonlinear inside the