| Message ID | 20190724232700.23327-2-rcampbell@nvidia.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/hmm: fixes for device private page migration | expand |
On Wed, Jul 24, 2019 at 04:26:58PM -0700, Ralph Campbell wrote: > Struct page for ZONE_DEVICE private pages uses the page->mapping and > and page->index fields while the source anonymous pages are migrated to > device private memory. This is so rmap_walk() can find the page when > migrating the ZONE_DEVICE private page back to system memory. > ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and > page->index fields when files are mapped into a process address space. > > Add comments to struct page and remove the unused "_zd_pad_1" field > to make this more clear. > > Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > Cc: Matthew Wilcox <willy@infradead.org> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Christoph Lameter <cl@linux.com> > Cc: Dave Hansen <dave.hansen@linux.intel.com> > Cc: Jérôme Glisse <jglisse@redhat.com> > Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> > Cc: Lai Jiangshan <jiangshanlai@gmail.com> > Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> > Cc: Pekka Enberg <penberg@kernel.org> > Cc: Randy Dunlap <rdunlap@infradead.org> > Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> > Cc: Christoph Hellwig <hch@lst.de> > Cc: Jason Gunthorpe <jgg@mellanox.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Linus Torvalds <torvalds@linux-foundation.org> > include/linux/mm_types.h | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) Ralph, you marked some of thes patches as mm/hmm, but I feel it is best if Andrew takes them through the normal -mm path. They don't touch hmm.c or mmu notifiers so I don't forsee conflicts, and I don't feel comfortable to review this code. Regards, Jason
On Wed, Jul 24, 2019 at 04:26:58PM -0700, Ralph Campbell wrote: > Struct page for ZONE_DEVICE private pages uses the page->mapping and > and page->index fields while the source anonymous pages are migrated to > device private memory. This is so rmap_walk() can find the page when > migrating the ZONE_DEVICE private page back to system memory. > ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and > page->index fields when files are mapped into a process address space. > > Add comments to struct page and remove the unused "_zd_pad_1" field > to make this more clear. I still think we should also fix up the layout, and I haven't seen a reply from Matthew justifying his curses for your patch that makes the struct page layout actually match how it is used.
On 7/24/19 6:22 PM, Jason Gunthorpe wrote: > On Wed, Jul 24, 2019 at 04:26:58PM -0700, Ralph Campbell wrote: >> Struct page for ZONE_DEVICE private pages uses the page->mapping and >> and page->index fields while the source anonymous pages are migrated to >> device private memory. This is so rmap_walk() can find the page when >> migrating the ZONE_DEVICE private page back to system memory. >> ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and >> page->index fields when files are mapped into a process address space. >> >> Add comments to struct page and remove the unused "_zd_pad_1" field >> to make this more clear. >> >> Signed-off-by: Ralph Campbell <rcampbell@nvidia.com> >> Reviewed-by: John Hubbard <jhubbard@nvidia.com> >> Cc: Matthew Wilcox <willy@infradead.org> >> Cc: Vlastimil Babka <vbabka@suse.cz> >> Cc: Christoph Lameter <cl@linux.com> >> Cc: Dave Hansen <dave.hansen@linux.intel.com> >> Cc: Jérôme Glisse <jglisse@redhat.com> >> Cc: "Kirill A . Shutemov" <kirill.shutemov@linux.intel.com> >> Cc: Lai Jiangshan <jiangshanlai@gmail.com> >> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> >> Cc: Pekka Enberg <penberg@kernel.org> >> Cc: Randy Dunlap <rdunlap@infradead.org> >> Cc: Andrey Ryabinin <aryabinin@virtuozzo.com> >> Cc: Christoph Hellwig <hch@lst.de> >> Cc: Jason Gunthorpe <jgg@mellanox.com> >> Cc: Andrew Morton <akpm@linux-foundation.org> >> Cc: Linus Torvalds <torvalds@linux-foundation.org> >> include/linux/mm_types.h | 11 ++++++++++- >> 1 file changed, 10 insertions(+), 1 deletion(-) > > Ralph, you marked some of thes patches as mm/hmm, but I feel it is > best if Andrew takes them through the normal -mm path. > > They don't touch hmm.c or mmu notifiers so I don't forsee conflicts, > and I don't feel comfortable to review this code. > > Regards, > Jason > Fine with me. I should have been clear in the cover letter which tree to target.
On 7/24/19 10:38 PM, Christoph Hellwig wrote: > On Wed, Jul 24, 2019 at 04:26:58PM -0700, Ralph Campbell wrote: >> Struct page for ZONE_DEVICE private pages uses the page->mapping and >> and page->index fields while the source anonymous pages are migrated to >> device private memory. This is so rmap_walk() can find the page when >> migrating the ZONE_DEVICE private page back to system memory. >> ZONE_DEVICE pmem backed fsdax pages also use the page->mapping and >> page->index fields when files are mapped into a process address space. >> >> Add comments to struct page and remove the unused "_zd_pad_1" field >> to make this more clear. > > I still think we should also fix up the layout, and I haven't seen > a reply from Matthew justifying his curses for your patch that makes > the struct page layout actually match how it is used. > Well, I can kind of see this both ways since ZONE_DEVICE MEMORY_DEVICE_DEVDAX and MEMORY_DEVICE_PCI_P2PDMA don't seem to use the 3 words like MEMORY_DEVICE_PRIVATE and MEMORY_DEVICE_FS_DAX. I like v3 because not all of the ZONE_DEVICE types are handled the same in regards to using the 3 words and there may be future ZONE_DEVICE types that use the 3 words differently which might require a union. I agree, I would like to hear from Matthew on his thoughts.
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 3a37a89eb7a7..6a7a1083b6fb 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -159,7 +159,16 @@ struct page { /** @pgmap: Points to the hosting device page map. */ struct dev_pagemap *pgmap; void *zone_device_data; - unsigned long _zd_pad_1; /* uses mapping */ + /* + * ZONE_DEVICE private pages are counted as being + * mapped so the next 3 words hold the mapping, index, + * and private fields from the source anonymous or + * page cache page while the page is migrated to device + * private memory. + * ZONE_DEVICE MEMORY_DEVICE_FS_DAX pages also + * use the mapping, index, and private fields when + * pmem backed DAX files are mapped. + */ }; /** @rcu_head: You can use this to free a page by RCU. */