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authorSantosh Shilimkar <santosh.shilimkar@oracle.com>2016-09-19 14:44:15 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-09-19 15:36:17 -0700
commitc8de641b1e9c5489aa6ca57b7836acd68e7563f1 (patch)
tree6cf2e5f733905522629ef39910f79709f9f78422 /mm
parent7cbdb4a286a60c5d519cb9223fe2134d26870d39 (diff)
downloadlinux-stericsson-c8de641b1e9c5489aa6ca57b7836acd68e7563f1.tar.gz
mm: fix the page_swap_info() BUG_ON check
Commit 62c230bc1790 ("mm: add support for a filesystem to activate swap files and use direct_IO for writing swap pages") replaced the swap_aops dirty hook from __set_page_dirty_no_writeback() with swap_set_page_dirty(). For normal cases without these special SWP flags code path falls back to __set_page_dirty_no_writeback() so the behaviour is expected to be the same as before. But swap_set_page_dirty() makes use of the page_swap_info() helper to get the swap_info_struct to check for the flags like SWP_FILE, SWP_BLKDEV etc as desired for those features. This helper has BUG_ON(!PageSwapCache(page)) which is racy and safe only for the set_page_dirty_lock() path. For the set_page_dirty() path which is often needed for cases to be called from irq context, kswapd() can toggle the flag behind the back while the call is getting executed when system is low on memory and heavy swapping is ongoing. This ends up with undesired kernel panic. This patch just moves the check outside the helper to its users appropriately to fix kernel panic for the described path. Couple of users of helpers already take care of SwapCache condition so I skipped them. Link: http://lkml.kernel.org/r/1473460718-31013-1-git-send-email-santosh.shilimkar@oracle.com Signed-off-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Joe Perches <joe@perches.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Rik van Riel <riel@redhat.com> Cc: David S. Miller <davem@davemloft.net> Cc: Jens Axboe <axboe@fb.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Hugh Dickins <hughd@google.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: <stable@vger.kernel.org> [4.7.x] 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/page_io.c3
-rw-r--r--mm/swapfile.c1
2 files changed, 3 insertions, 1 deletions
diff --git a/mm/page_io.c b/mm/page_io.c
index 16bd82fad38c..eafe5ddc2b54 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -264,6 +264,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
int ret;
struct swap_info_struct *sis = page_swap_info(page);
+ BUG_ON(!PageSwapCache(page));
if (sis->flags & SWP_FILE) {
struct kiocb kiocb;
struct file *swap_file = sis->swap_file;
@@ -337,6 +338,7 @@ int swap_readpage(struct page *page)
int ret = 0;
struct swap_info_struct *sis = page_swap_info(page);
+ BUG_ON(!PageSwapCache(page));
VM_BUG_ON_PAGE(!PageLocked(page), page);
VM_BUG_ON_PAGE(PageUptodate(page), page);
if (frontswap_load(page) == 0) {
@@ -386,6 +388,7 @@ int swap_set_page_dirty(struct page *page)
if (sis->flags & SWP_FILE) {
struct address_space *mapping = sis->swap_file->f_mapping;
+ BUG_ON(!PageSwapCache(page));
return mapping->a_ops->set_page_dirty(page);
} else {
return __set_page_dirty_no_writeback(page);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 78cfa292a29a..2657accc6e2b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2724,7 +2724,6 @@ int swapcache_prepare(swp_entry_t entry)
struct swap_info_struct *page_swap_info(struct page *page)
{
swp_entry_t swap = { .val = page_private(page) };
- BUG_ON(!PageSwapCache(page));
return swap_info[swp_type(swap)];
}