• Hugh Dickins's avatar
    mm/khugepaged: fix crashes due to misaccounted holes · aaa52e34
    Hugh Dickins authored
    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
    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
    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: 800d8c63 ("shmem: add huge pages support")
    Fixes: f3f0e1d2 ("khugepaged: add support of collapse for tmpfs/shmem pages")
    Signed-off-by: default avatarHugh Dickins <hughd@google.com>
    Acked-by: default avatarKirill 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: default avatarAndrew Morton <akpm@linux-foundation.org>
    Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
khugepaged.c 48 KB