Maxim Patlasov <mpatla...@virtuozzo.com> writes:
> cbt_page_alloc() drops cbt->lock before calling alloc_page(), > then re-acquires it. It's safer to re-check that cbt->map[idx] > is still NULL after re-acquiring the lock. > > Signed-off-by: Maxim Patlasov <mpatla...@virtuozzo.com> Indeed. Ack. > --- > block/blk-cbt.c | 7 ++++++- > 1 file changed, 6 insertions(+), 1 deletion(-) > > diff --git a/block/blk-cbt.c b/block/blk-cbt.c > index 8ba52fb..14ad1a2 100644 > --- a/block/blk-cbt.c > +++ b/block/blk-cbt.c > @@ -128,7 +128,12 @@ static int cbt_page_alloc(struct cbt_info **cbt_pp, > unsigned long idx, > spin_unlock_irq(&cbt->lock); > return -ENOMEM; > } > - cbt->map[idx] = page; > + > + if (likely(CBT_PAGE(cbt, idx) == NULL)) > + cbt->map[idx] = page; > + else > + __free_page(page); > + > page = NULL; > spin_unlock_irq(&cbt->lock); >
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