On Fri, 5 Aug 2016, Hillf Danton wrote:
> Hi all
>
> Currently in mainline we do block account if the flags parameter
> carries VM_NORESERVE.
Yes. (VM_NORESERVE being set in tmpfs file flags,
but usually not on SysV SHM and mmaps of /dev/zero.)
>
> But blocks should be accounted if reserved, as shown by the
> following diff.
Blocks should be accounted one by one as they are instantiated
(tmpfs), unless the total size was all reserved upfront (SHM).
>
> Am I missing anything?
Apparently, but I'm not sure what. Maybe the comments
above shmem_acct_size() and shmem_acct_block() will help.
Hugh
>
> thanks
> Hillf
>
> --- a/mm/shmem.c Fri Aug 5 14:01:59 2016
> +++ b/mm/shmem.c Fri Aug 5 14:36:31 2016
> @@ -168,7 +168,7 @@ static inline int shmem_reacct_size(unsi
> */
> static inline int shmem_acct_block(unsigned long flags, long pages)
> {
> - if (!(flags & VM_NORESERVE))
> + if (flags & VM_NORESERVE)
> return 0;
>
> return security_vm_enough_memory_mm(current->mm,
> @@ -177,7 +177,7 @@ static inline int shmem_acct_block(unsig
>
> static inline void shmem_unacct_blocks(unsigned long flags, long pages)
> {
> - if (flags & VM_NORESERVE)
> + if (!(flags & VM_NORESERVE))
> vm_unacct_memory(pages * VM_ACCT(PAGE_SIZE));
> }
>
> --
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