On Fri, May 18, 2018 at 2:46 AM, Christoph Hellwig <hch@xxxxxx> wrote:
> This looks reasonable to me. A few more comments below.
>
>> This patch replaces and consolidates patch 2 [1] and 4 [2] from the v9
>> series [3] for "dax: fix dma vs truncate/hole-punch".
>
> Can you repost the whole series? Otherwise things might get a little
> too confusing.
Sure thing.
>> WARN_ON(IS_ENABLED(CONFIG_ARCH_HAS_PMEM_API));
>> + return 0;
>> } else if (pfn_t_devmap(pfn)) {
>> + struct dev_pagemap *pgmap;
>
> This should probably become something like:
>
> bool supported = false;
>
> ...
>
>
> if (IS_ENABLED(CONFIG_FS_DAX_LIMITED) && pfn_t_special(pfn)) {
> ...
> supported = true;
> } else if (pfn_t_devmap(pfn)) {
> pgmap = get_dev_pagemap(pfn_t_to_pfn(pfn), NULL);
> if (pgmap && pgmap->type == MEMORY_DEVICE_FS_DAX)
> supported = true;
> put_dev_pagemap(pgmap);
> }
>
> if (!supported) {
> pr_debug("VFS (%s): error: dax support not enabled\n",
> sb->s_id);
> return -EOPNOTSUPP;
> }
> return 0;
Looks good, will do.
>> + select DEV_PAGEMAP_OPS if (ZONE_DEVICE && !FS_DAX_LIMITED)
>
> Btw, what was the reason again we couldn't get rid of FS_DAX_LIMITED?
The last I heard from Gerald they were still mildly interested in
keeping the dccssblk dax support going with this limited mode, and
threatened to add full page support at a later date:
---
From: Gerald
dcssblk seems to work fine, I did not see any SIGBUS while "executing
in place" from dcssblk with the current upstream kernel, maybe because
we only use dcssblk with fs dax in read-only mode.
Anyway, the dcssblk change is fine with me. I will look into adding
struct pages for dcssblk memory later, to make it work again with
this change, but for now I do not know of anyone needing this in the
upstream kernel.
https://www.spinics.net/lists/linux-xfs/msg14628.html
---
>> +void generic_dax_pagefree(struct page *page, void *data)
>> +{
>> + wake_up_var(&page->_refcount);
>> +}
>> +EXPORT_SYMBOL_GPL(generic_dax_pagefree);
>
> Why is this here and exported instead of static in drivers/nvdimm/pmem.c?
I was thinking it did not belong to the pmem driver, but you're right
unless / until we grow another fsdax capable driver this detail can
stay internal to the pmem driver.
