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    Subject[PATCH 5.13 772/800] mm/zswap.c: fix two bugs in zswap_writeback_entry()
    Date
    From: Miaohe Lin <linmiaohe@huawei.com>

    [ Upstream commit 46b76f2e09dc35f70aca2f4349eb0d158f53fe93 ]

    In the ZSWAP_SWAPCACHE_FAIL and ZSWAP_SWAPCACHE_EXIST case, we forgot to
    call zpool_unmap_handle() when zpool can't sleep. And we might sleep in
    zswap_get_swap_cache_page() while zpool can't sleep. To fix all of these,
    zpool_unmap_handle() should be done before zswap_get_swap_cache_page()
    when zpool can't sleep.

    Link: https://lkml.kernel.org/r/20210522092242.3233191-4-linmiaohe@huawei.com
    Fixes: fc6697a89f56 ("mm/zswap: add the flag can_sleep_mapped")
    Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
    Cc: Colin Ian King <colin.king@canonical.com>
    Cc: Dan Streetman <ddstreet@ieee.org>
    Cc: Nathan Chancellor <nathan@kernel.org>
    Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
    Cc: Seth Jennings <sjenning@redhat.com>
    Cc: Tian Tao <tiantao6@hisilicon.com>
    Cc: Vitaly Wool <vitaly.wool@konsulko.com>
    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>
    ---
    mm/zswap.c | 17 +++++++----------
    1 file changed, 7 insertions(+), 10 deletions(-)

    diff --git a/mm/zswap.c b/mm/zswap.c
    index 20763267a219..706e0f98125a 100644
    --- a/mm/zswap.c
    +++ b/mm/zswap.c
    @@ -967,6 +967,13 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
    spin_unlock(&tree->lock);
    BUG_ON(offset != entry->offset);

    + src = (u8 *)zhdr + sizeof(struct zswap_header);
    + if (!zpool_can_sleep_mapped(pool)) {
    + memcpy(tmp, src, entry->length);
    + src = tmp;
    + zpool_unmap_handle(pool, handle);
    + }
    +
    /* try to allocate swap cache page */
    switch (zswap_get_swap_cache_page(swpentry, &page)) {
    case ZSWAP_SWAPCACHE_FAIL: /* no memory or invalidate happened */
    @@ -982,17 +989,7 @@ static int zswap_writeback_entry(struct zpool *pool, unsigned long handle)
    case ZSWAP_SWAPCACHE_NEW: /* page is locked */
    /* decompress */
    acomp_ctx = raw_cpu_ptr(entry->pool->acomp_ctx);
    -
    dlen = PAGE_SIZE;
    - src = (u8 *)zhdr + sizeof(struct zswap_header);
    -
    - if (!zpool_can_sleep_mapped(pool)) {
    -
    - memcpy(tmp, src, entry->length);
    - src = tmp;
    -
    - zpool_unmap_handle(pool, handle);
    - }

    mutex_lock(acomp_ctx->mutex);
    sg_init_one(&input, src, entry->length);
    --
    2.30.2


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