mm/khugepaged: fix crashes due to misaccounted holes
commit aaa52e340073b7f4593b3c4ddafcafa70cf838b5 upstream.
Huge tmpfs testing on a shortish file mapped into a pmd-rounded extent
hit shmem_evict_inode()'s WARN_ON(inode->i_blocks) followed by
clear_inode()'s BUG_ON(inode->i_data.nrpages) when the file was later
closed and unlinked.
khugepaged's collapse_shmem() was forgetting to update mapping->nrpages
on the rollback path, after it had added but then needs to undo some
holes.
There is indeed an irritating asymmetry between shmem_charge(), whose
callers want it to increment nrpages after successfully accounting
blocks, and shmem_uncharge(), when __delete_from_page_cache() already
decremented nrpages itself: oh well, just add a comment on that to them
both.
And shmem_recalc_inode() is supposed to be called when the accounting is
expected to be in balance (so it can deduce from imbalance that reclaim
discarded some pages): so change shmem_charge() to update nrpages
earlier (though it's rare for the difference to matter at all).
Link: http://lkml.kernel.org/r/alpine.LSU.2.11.1811261523450.2275@eggly.anvils
Fixes: 800d8c63b2e98 ("shmem: add huge pages support")
Fixes: f3f0e1d2150b2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: <stable@vger.kernel.org> [4.8+]
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>
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 62de241..3f7bfd9 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -1538,8 +1538,10 @@ static void collapse_shmem(struct mm_struct *mm,
*hpage = NULL;
} else {
/* Something went wrong: rollback changes to the radix-tree */
- shmem_uncharge(mapping->host, nr_none);
spin_lock_irq(&mapping->tree_lock);
+ mapping->nrpages -= nr_none;
+ shmem_uncharge(mapping->host, nr_none);
+
radix_tree_for_each_slot(slot, &mapping->page_tree, &iter,
start) {
if (iter.index >= end)