Re: [PATCH] dax: Fix xarray entry association for mixed mappings

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Jun 6, 2019 at 2:10 AM Jan Kara <jack@xxxxxxx> wrote:
>
> When inserting entry into xarray, we store mapping and index in
> corresponding struct pages for memory error handling. When it happened
> that one process was mapping file at PMD granularity while another
> process at PTE granularity, we could wrongly deassociate PMD range and
> then reassociate PTE range leaving the rest of struct pages in PMD range
> without mapping information which could later cause missed notifications
> about memory errors. Fix the problem by calling the association /
> deassociation code if and only if we are really going to update the
> xarray (deassociating and associating zero or empty entries is just
> no-op so there's no reason to complicate the code with trying to avoid
> the calls for these cases).

Looks good to me, I assume this also needs:

Cc: <stable@xxxxxxxxxxxxxxx>
Fixes: d2c997c0f145 ("fs, dax: use page->mapping to warn if truncate
collides with a busy page")

>
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
>  fs/dax.c | 9 ++++-----
>  1 file changed, 4 insertions(+), 5 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index f74386293632..9fd908f3df32 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -728,12 +728,11 @@ static void *dax_insert_entry(struct xa_state *xas,
>
>         xas_reset(xas);
>         xas_lock_irq(xas);
> -       if (dax_entry_size(entry) != dax_entry_size(new_entry)) {
> +       if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
> +               void *old;
> +
>                 dax_disassociate_entry(entry, mapping, false);
>                 dax_associate_entry(new_entry, mapping, vmf->vma, vmf->address);
> -       }
> -
> -       if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
>                 /*
>                  * Only swap our new entry into the page cache if the current
>                  * entry is a zero page or an empty entry.  If a normal PTE or
> @@ -742,7 +741,7 @@ static void *dax_insert_entry(struct xa_state *xas,
>                  * existing entry is a PMD, we will just leave the PMD in the
>                  * tree and dirty it if necessary.
>                  */
> -               void *old = dax_lock_entry(xas, new_entry);
> +               old = dax_lock_entry(xas, new_entry);
>                 WARN_ON_ONCE(old != xa_mk_value(xa_to_value(entry) |
>                                         DAX_LOCKED));
>                 entry = new_entry;
> --
> 2.16.4
>



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux