Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]
Groups > linux.kernel > #1359687
| From | Vlastimil Babka <vbabka@suse.cz> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH] UBIFS: Implement ->migratepage() |
| Date | 2016-03-17 11:00 +0100 |
| Message-ID | <rdCSL-5Ht-41@gated-at.bofh.it> (permalink) |
| References | <rdqye-5Es-7@gated-at.bofh.it> <rdsA1-78W-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
+CC Hugh, Mel
On 03/16/2016 11:55 PM, Richard Weinberger wrote:
> From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
>
> When using CMA during page migrations UBIFS might get confused
It shouldn't be CMA specific, the same code runs from compaction,
autonuma balancing...
> and the following assert triggers:
> UBIFS assert failed in ubifs_set_page_dirty at 1451 (pid 436)
>
> UBIFS is using PagePrivate() which can have different meanings across
> filesystems. Therefore the generic page migration code cannot handle this
> case correctly.
> We have to implement our own migration function which basically does a
> plain copy but also duplicates the page private flag.
Lack of PagePrivate() migration is surely a bug, but at a glance of how
UBIFS uses the flag, it's more about accounting, it shouldn't prevent a
page from being marked PageDirty()?
I suspect your initial bug (which is IIUC the fact that there's a dirty
pte, but PageDirty(page) is false) comes from the generic
fallback_migrate_page() which does:
if (PageDirty(page)) {
/* Only writeback pages in full synchronous migration */
if (mode != MIGRATE_SYNC)
return -EBUSY;
return writeout(mapping, page);
}
And writeout() seems to Clear PageDirty() through
clear_page_dirty_for_io() but I'm not so sure about the pte (or pte's in
all rmaps). But this comment in the latter function:
* Yes, Virginia, this is indeed insane.
scared me enough to not investigate further. Hopefully the people I CC'd
understand more about page migration than me. I'm just an user :)
In any case, this patch would solve both lack of PageDirty() transfer,
and avoid the path leading from fallback_migrate_page() to writeout().
But I'm not confident enough here to ack it.
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> [rw: Massaged changelog]
> Signed-off-by: Richard Weinberger <richard@nod.at>
> ---
> fs/ubifs/file.c | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
> index 0edc128..48b2944 100644
> --- a/fs/ubifs/file.c
> +++ b/fs/ubifs/file.c
> @@ -52,6 +52,7 @@
> #include "ubifs.h"
> #include <linux/mount.h>
> #include <linux/slab.h>
> +#include <linux/migrate.h>
>
> static int read_block(struct inode *inode, void *addr, unsigned int block,
> struct ubifs_data_node *dn)
> @@ -1452,6 +1453,24 @@ static int ubifs_set_page_dirty(struct page *page)
> return ret;
> }
>
> +static int ubifs_migrate_page(struct address_space *mapping,
> + struct page *newpage, struct page *page, enum migrate_mode mode)
> +{
> + int rc;
> +
> + rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode, 0);
> + if (rc != MIGRATEPAGE_SUCCESS)
> + return rc;
> +
> + if (PagePrivate(page)) {
> + ClearPagePrivate(page);
> + SetPagePrivate(newpage);
> + }
> +
> + migrate_page_copy(newpage, page);
> + return MIGRATEPAGE_SUCCESS;
> +}
> +
> static int ubifs_releasepage(struct page *page, gfp_t unused_gfp_flags)
> {
> /*
> @@ -1591,6 +1610,7 @@ const struct address_space_operations ubifs_file_address_operations = {
> .write_end = ubifs_write_end,
> .invalidatepage = ubifs_invalidatepage,
> .set_page_dirty = ubifs_set_page_dirty,
> + .migratepage = ubifs_migrate_page,
> .releasepage = ubifs_releasepage,
> };
>
>
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-15 15:20 +0100
Re: Page migration issue with UBIFS "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-03-15 16:20 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-15 16:30 +0100
Re: Page migration issue with UBIFS Christoph Hellwig <hch@infradead.org> - 2016-03-15 16:40 +0100
Re: Page migration issue with UBIFS "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-03-15 16:50 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-15 16:40 +0100
Re: Page migration issue with UBIFS Christoph Hellwig <hch@infradead.org> - 2016-03-15 16:40 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-15 17:10 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-16 00:20 +0100
Re: Page migration issue with UBIFS "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-16 15:30 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-16 21:50 +0100
[PATCH] UBIFS: Implement ->migratepage() Richard Weinberger <richard@nod.at> - 2016-03-17 00:00 +0100
Re: [PATCH] UBIFS: Implement ->migratepage() Vlastimil Babka <vbabka@suse.cz> - 2016-03-17 11:00 +0100
Re: [PATCH] UBIFS: Implement ->migratepage() Richard Weinberger <richard@nod.at> - 2016-03-26 00:00 +0100
Re: Page migration issue with UBIFS Joonsoo Kim <iamjoonsoo.kim@lge.com> - 2016-03-17 08:20 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-17 09:20 +0100
Re: Page migration issue with UBIFS Joonsoo Kim <js1304@gmail.com> - 2016-03-17 16:20 +0100
Re: Page migration issue with UBIFS Andrew Morton <akpm@linux-foundation.org> - 2016-03-22 00:10 +0100
Re: Page migration issue with UBIFS Richard Weinberger <richard@nod.at> - 2016-03-22 00:10 +0100
Re: Page migration issue with UBIFS "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-03-16 15:30 +0100
Re: Page migration issue with UBIFS Christoph Hellwig <hch@infradead.org> - 2016-03-21 16:30 +0100
Re: Page migration issue with UBIFS Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-03-17 16:30 +0100
csiph-web