@@ -1362,7 +1362,15 @@ static int shmem_writepage(struct page *
swp_entry_t swap;
pgoff_t index;
- VM_BUG_ON_PAGE(PageCompound(page), page);
+ /*
+ * If /sys/kernel/mm/transparent_hugepage/shmem_enabled is "force",
+ * then drivers/gpu/drm/i915/gem/i915_gem_shmem.c gets huge pages,
+ * and its shmem_writeback() needs them to be split when swapping.
+ */
+ if (PageTransCompound(page))
+ if (split_huge_page(page) < 0)
+ goto redirty;
+
BUG_ON(!PageLocked(page));
mapping = page->mapping;
index = page->index;
The patch titled Subject: shmem: shmem_writepage() split unlikely i915 THP has been added to the -mm tree. Its filename is shmem-shmem_writepage-split-unlikely-i915-thp.patch This patch should soon appear at http://ozlabs.org/~akpm/mmots/broken-out/shmem-shmem_writepage-split-unlikely-i915-thp.patch and later at http://ozlabs.org/~akpm/mmotm/broken-out/shmem-shmem_writepage-split-unlikely-i915-thp.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Hugh Dickins <hughd@google.com> Subject: shmem: shmem_writepage() split unlikely i915 THP drivers/gpu/drm/i915/gem/i915_gem_shmem.c contains a shmem_writeback() which calls shmem_writepage() from a shrinker: that usually works well enough; but if /sys/kernel/mm/transparent_hugepage/shmem_enabled has been set to "force" (documented as "Force the huge option on for all - very useful for testing"), shmem_writepage() is surprised to be called with a huge page, and crashes on the VM_BUG_ON_PAGE(PageCompound) (I did not find out where the crash happens when CONFIG_DEBUG_VM is off). LRU page reclaim always splits the shmem huge page first: I'd prefer not to demand that of i915, so check and split compound in shmem_writepage(). Link: http://lkml.kernel.org/r/alpine.LSU.2.11.2008301401390.5954@eggly.anvils Fixes: 2d6692e642e7 ("drm/i915: Start writeback from the shrinker") Signed-off-by: Hugh Dickins <hughd@google.com> Cc: Alex Shi <alex.shi@linux.alibaba.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.com> Cc: Mike Kravetz <mike.kravetz@oracle.com> Cc: Qian Cai <cai@lca.pw> Cc: Shakeel Butt <shakeelb@google.com> Cc: <stable@vger.kernel.org> [5.3+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> --- mm/shmem.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-)