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| /openbmc/linux/drivers/gpu/drm/i915/gem/selftests/ |
| H A D | huge_pages.c | diff 6341eb6f39bb76018676dc85e01596bf32a592f6 Tue Sep 21 09:21:16 CDT 2021 Matthew Auld <matthew.auld@intel.com> drm/i915/selftests: exercise shmem_writeback with THP
In commit:
commit 1e6decf30af5c5c75445ed6ad4e65a26de578a03
Author: Hugh Dickins <hughd@google.com>
Date: Thu Sep 2 14:54:43 2021 -0700
shmem: shmem_writepage() split unlikely i915 THP
it looks THP + shmem_writeback was an unexpected combination, and ends up
hitting some BUG_ON, but it also looks like that is now fixed.
While the IGTs did eventually hit this(although not during pre-merge it
seems), it's likely worthwhile adding some explicit coverage for this
scenario in the shrink_thp selftest.
References: https://gitlab.freedesktop.org/drm/intel/-/issues/4166
Signed-off-by: Matthew Auld <matthew.auld@intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210921142116.3807946-1-matthew.auld@intel.com
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| /openbmc/linux/mm/ |
| H A D | shmem.c | diff 1e6decf30af5c5c75445ed6ad4e65a26de578a03 Thu Sep 02 16:54:43 CDT 2021 Hugh Dickins <hughd@google.com> 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 "always" (intended to be usable) or "force" (forces huge everywhere
for easy 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().
Patch history: when first sent last year
http://lkml.kernel.org/r/alpine.LSU.2.11.2008301401390.5954@eggly.anvils
https://lore.kernel.org/linux-mm/20200919042009.bomzxmrg7%25akpm@linux-foundation.org/
Matthew Wilcox noticed that tail pages were wrongly left clean. This
version brackets the split with Set and Clear PageDirty as he suggested:
which works very well, even if it falls short of our aspirations. And
recently I realized that the crash is not limited to the testing option
"force", but affects "always" too: which is more important to fix.
Link: https://lkml.kernel.org/r/bac6158c-8b3d-4dca-cffc-4982f58d9794@google.com
Fixes: 2d6692e642e7 ("drm/i915: Start writeback from the shrinker")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Shakeel Butt <shakeelb@google.com>
Acked-by: Yang Shi <shy828301@gmail.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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