Messages in this thread |  | | Subject | Re: [PATCH v3 0/2] Align mmap address for DAX pmd mappings | From | Toshi Kani <> | Date | Thu, 21 Apr 2016 20:59:38 -0400 |
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On 4/21/2016 8:22 PM, Matthew Wilcox wrote: > On Thu, Apr 21, 2016 at 07:43:39PM -0400, Toshi Kani wrote: >> On 4/21/2016 4:21 PM, Mike Kravetz wrote: >>> Might want to keep the future possibility of PUD_SIZE THP in mind? >> Yes, this is why the func name does not say 'pmd'. It can be extended to >> support >> PUD_SIZE in future. > Sure ... but what does that look like? I think it should look a little > like this:
Yes, I had something similar in mind, too. Do you want me to use this version without the call with PUD_SIZE?
> > unsigned long __thp_get_unmapped_area(struct file *filp, unsigned long len, > loff_t off, unsigned long flags, unsigned long size); > { > unsigned long addr; > loff_t off_end = off + len; > loff_t off_align = round_up(off, size); > unsigned long len_size; > > if ((off_end <= off_align) || ((off_end - off_align) < size)) > return NULL; > > len_size = len + size; > if ((len_size < len) || (off + len_size) < off) > return NULL; > > addr = current->mm->get_unmapped_area(filp, NULL, len_size, > off >> PAGE_SHIFT, flags); > if (IS_ERR_VALUE(addr)) > return NULL; > > addr += (off - addr) & (size - 1); > return addr; > } > > unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr, > unsigned long len, unsigned long pgoff, unsigned long flags) > { > loff_t off = (loff_t)pgoff << PAGE_SHIFT; > > if (addr) > goto out; > if (IS_DAX(filp->f_mapping->host) && !IS_ENABLED(CONFIG_FS_DAX_PMD)) > goto out; > /* Kirill, please fill in the right condition here for THP pagecache */ > > addr = __thp_get_unmapped_area(filp, len, off, flags, PUD_SIZE); > if (addr) > return addr; > addr = __thp_get_unmapped_area(filp, len, off, flags, PMD_SIZE); > if (addr) > return addr; > > out: > return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags); > } > > By the way, I added an extra check here, when we add len and size > (PMD_SIZE in the original), we need to make sure that doesn't wrap. > NB: I'm not even compiling these suggestions, just throwing them out > here as ideas to be criticised.
Yes, I agree with the extra check. Thanks for pointing this out.
> > Also, len_size is a stupid name, but I can't think of a better one.
How about len_pad?
Thanks, -Toshi
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