[PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7 - Kernel

This is a discussion on [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7 - Kernel ; [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7 Prevent a page with a physical memory error from being placed back on the LRU. A new page flag (PG_memerror) is added if CONFIG_PAGEFLAGS_EXTENDED is defined. Signed-off-by: ...

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Thread: [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

  1. [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

    [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

    Prevent a page with a physical memory error from being placed back
    on the LRU. A new page flag (PG_memerror) is added if
    CONFIG_PAGEFLAGS_EXTENDED is defined.

    Signed-off-by: Russ Anderson
    Reviewed-by: Christoph Lameter

    ---
    include/linux/page-flags.h | 18 ++++++++++++++++--
    mm/migrate.c | 31 ++++++++++++++++++++++++++++++-
    mm/page_alloc.c | 13 ++++++++-----
    3 files changed, 54 insertions(+), 8 deletions(-)

    Index: linux/mm/page_alloc.c
    ================================================== =================
    --- linux.orig/mm/page_alloc.c 2008-07-18 15:15:48.000000000 -0500
    +++ linux/mm/page_alloc.c 2008-07-18 15:16:09.000000000 -0500
    @@ -602,10 +602,10 @@ static int prep_new_page(struct page *pa
    bad_page(page);

    /*
    - * For now, we report if PG_reserved was found set, but do not
    - * clear it, and do not allocate the page: as a safety net.
    + * For now, we report if PG_reserved or PG_memerror was found set, but
    + * do not clear it, and do not allocate the page: as a safety net.
    */
    - if (PageReserved(page))
    + if (PageReserved(page) || PageMemError(page))
    return 1;

    page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
    @@ -2475,8 +2475,11 @@ static void setup_zone_migrate_reserve(s
    continue;
    page = pfn_to_page(pfn);

    - /* Blocks with reserved pages will never free, skip them. */
    - if (PageReserved(page))
    + /*
    + * Blocks with reserved pages or memory errors will never
    + * free, skip them.
    + */
    + if (PageReserved(page) || PageMemError(page))
    continue;

    block_migratetype = get_pageblock_migratetype(page);
    Index: linux/mm/migrate.c
    ================================================== =================
    --- linux.orig/mm/migrate.c 2008-07-18 15:15:48.000000000 -0500
    +++ linux/mm/migrate.c 2008-07-18 15:16:09.000000000 -0500
    @@ -720,7 +720,25 @@ unlock:
    * restored.
    */
    list_del(&page->lru);
    - move_to_lru(page);
    + if (PageMemError(page))
    + if (rc == 0)
    + /*
    + * A page with a memory error that has
    + * been migrated will not be moved to
    + * the LRU.
    + */
    + goto move_newpage;
    + else
    + /*
    + * The page failed to migrate and will not
    + * be added to the bad page list. Clearing
    + * the error bit will allow another attempt
    + * to migrate if it gets another correctable
    + * error.
    + */
    + ClearPageMemError(page);
    +
    + move_to_lru(page);
    }

    move_newpage:
    @@ -790,6 +808,17 @@ int migrate_pages(struct list_head *from
    }
    }
    }
    +
    + if (rc != 0)
    + list_for_each_entry_safe(page, page2, from, lru)
    + if (PageMemError(page))
    + /*
    + * The page failed to migrate. Clearing
    + * the error bit will allow another attempt
    + * to migrate if it gets another correctable
    + * error.
    + */
    + ClearPageMemError(page);
    rc = 0;
    out:
    if (!swapwrite)
    Index: linux/include/linux/page-flags.h
    ================================================== =================
    --- linux.orig/include/linux/page-flags.h 2008-07-18 15:15:48.000000000 -0500
    +++ linux/include/linux/page-flags.h 2008-07-18 15:16:09.000000000 -0500
    @@ -84,6 +84,7 @@ enum pageflags {
    PG_private, /* If pagecache, has fs-private data */
    PG_writeback, /* Page is under writeback */
    #ifdef CONFIG_PAGEFLAGS_EXTENDED
    + PG_memerror, /* Page has a physical memory error */
    PG_head, /* A head page */
    PG_tail, /* A tail page */
    #else
    @@ -132,15 +133,21 @@ static inline int TestSetPage##uname(str
    static inline int TestClearPage##uname(struct page *page) \
    { return test_and_clear_bit(PG_##lname, &page->flags); }

    +#define PAGEFLAGMASK(uname, lname) \
    +static inline int PAGEMASK_##uname(void) \
    + { return (1 << PG_##lname); }

    #define PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
    - SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname)
    + SETPAGEFLAG(uname, lname) CLEARPAGEFLAG(uname, lname) \
    + PAGEFLAGMASK(uname, lname)

    #define __PAGEFLAG(uname, lname) TESTPAGEFLAG(uname, lname) \
    __SETPAGEFLAG(uname, lname) __CLEARPAGEFLAG(uname, lname)

    #define PAGEFLAG_FALSE(uname) \
    static inline int Page##uname(struct page *page) \
    + { return 0; } \
    +static inline int PAGEMASK_##uname(void) \
    { return 0; }

    #define TESTSCFLAG(uname, lname) \
    @@ -308,9 +315,16 @@ static inline void __ClearPageTail(struc

    #endif /* !PAGEFLAGS_EXTENDED */

    +#ifdef CONFIG_PAGEFLAGS_EXTENDED
    +PAGEFLAG(MemError, memerror)
    +#else
    +PAGEFLAG_FALSE(MemError)
    +#endif
    +
    #define PAGE_FLAGS (1 << PG_lru | 1 << PG_private | 1 << PG_locked | \
    1 << PG_buddy | 1 << PG_writeback | \
    - 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active)
    + 1 << PG_slab | 1 << PG_swapcache | 1 << PG_active) |\
    + PAGEMASK_MemError()

    /*
    * Flags checked in bad_page(). Pages on the free list should not have
    --
    Russ Anderson, OS RAS/Partitioning Project Lead
    SGI - Silicon Graphics Inc rja@sgi.com
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  2. Re: [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

    On Saturday 19 July 2008 06:36, Russ Anderson wrote:
    > [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7
    >
    > Prevent a page with a physical memory error from being placed back
    > on the LRU. A new page flag (PG_memerror) is added if
    > CONFIG_PAGEFLAGS_EXTENDED is defined.
    >
    > Signed-off-by: Russ Anderson
    > Reviewed-by: Christoph Lameter
    >
    > ---
    > include/linux/page-flags.h | 18 ++++++++++++++++--
    > mm/migrate.c | 31 ++++++++++++++++++++++++++++++-
    > mm/page_alloc.c | 13 ++++++++-----
    > 3 files changed, 54 insertions(+), 8 deletions(-)
    >
    > Index: linux/mm/page_alloc.c
    > ================================================== =================
    > --- linux.orig/mm/page_alloc.c 2008-07-18 15:15:48.000000000 -0500
    > +++ linux/mm/page_alloc.c 2008-07-18 15:16:09.000000000 -0500
    > @@ -602,10 +602,10 @@ static int prep_new_page(struct page *pa
    > bad_page(page);
    >
    > /*
    > - * For now, we report if PG_reserved was found set, but do not
    > - * clear it, and do not allocate the page: as a safety net.
    > + * For now, we report if PG_reserved or PG_memerror was found set, but
    > + * do not clear it, and do not allocate the page: as a safety net.
    > */
    > - if (PageReserved(page))
    > + if (PageReserved(page) || PageMemError(page))
    > return 1;
    >
    > page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
    > @@ -2475,8 +2475,11 @@ static void setup_zone_migrate_reserve(s
    > continue;
    > page = pfn_to_page(pfn);
    >
    > - /* Blocks with reserved pages will never free, skip them. */
    > - if (PageReserved(page))
    > + /*
    > + * Blocks with reserved pages or memory errors will never
    > + * free, skip them.
    > + */
    > + if (PageReserved(page) || PageMemError(page))
    > continue;
    >
    > block_migratetype = get_pageblock_migratetype(page);


    I don't like adding more branches like this into fastpaths like this. It
    would make a lot more sense to me if you just had some private module that
    does the job of isolating the page from the lru and/or elevating their
    refcount so that they do not get put back on freelists.

    Migration may need something to perhaps allow migrations of pages not on
    LRU lists but have PageMemError set which is OK, but I really don't like
    adding code and branches to page_alloc.c if possible....

    Thanks,
    Nick
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  3. Re: [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

    On Tue, Jul 22, 2008 at 12:42:10PM +1000, Nick Piggin wrote:
    > On Saturday 19 July 2008 06:36, Russ Anderson wrote:
    > > [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7
    > >
    > > Prevent a page with a physical memory error from being placed back
    > > on the LRU. A new page flag (PG_memerror) is added if
    > > CONFIG_PAGEFLAGS_EXTENDED is defined.
    > >
    > > Signed-off-by: Russ Anderson
    > > Reviewed-by: Christoph Lameter
    > >
    > > ---
    > > include/linux/page-flags.h | 18 ++++++++++++++++--
    > > mm/migrate.c | 31 ++++++++++++++++++++++++++++++-
    > > mm/page_alloc.c | 13 ++++++++-----
    > > 3 files changed, 54 insertions(+), 8 deletions(-)
    > >
    > > Index: linux/mm/page_alloc.c
    > > ================================================== =================
    > > --- linux.orig/mm/page_alloc.c 2008-07-18 15:15:48.000000000 -0500
    > > +++ linux/mm/page_alloc.c 2008-07-18 15:16:09.000000000 -0500
    > > @@ -602,10 +602,10 @@ static int prep_new_page(struct page *pa
    > > bad_page(page);
    > >
    > > /*
    > > - * For now, we report if PG_reserved was found set, but do not
    > > - * clear it, and do not allocate the page: as a safety net.
    > > + * For now, we report if PG_reserved or PG_memerror was found set, but
    > > + * do not clear it, and do not allocate the page: as a safety net.
    > > */
    > > - if (PageReserved(page))
    > > + if (PageReserved(page) || PageMemError(page))
    > > return 1;
    > >
    > > page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
    > > @@ -2475,8 +2475,11 @@ static void setup_zone_migrate_reserve(s
    > > continue;
    > > page = pfn_to_page(pfn);
    > >
    > > - /* Blocks with reserved pages will never free, skip them. */
    > > - if (PageReserved(page))
    > > + /*
    > > + * Blocks with reserved pages or memory errors will never
    > > + * free, skip them.
    > > + */
    > > + if (PageReserved(page) || PageMemError(page))
    > > continue;
    > >
    > > block_migratetype = get_pageblock_migratetype(page);

    >
    > I don't like adding more branches like this into fastpaths like this. It
    > would make a lot more sense to me if you just had some private module that
    > does the job of isolating the page from the lru and/or elevating their
    > refcount so that they do not get put back on freelists.


    That is how it works. If PageMemError is set the migration code
    leaves the page with an elevated refcount. The PageMemError() check
    was to avoid reallocating the page was an additional safty net.
    I'll pull the checks.

    > Migration may need something to perhaps allow migrations of pages not on
    > LRU lists but have PageMemError set which is OK, but I really don't like
    > adding code and branches to page_alloc.c if possible....
    >
    > Thanks,
    > Nick


    --
    Russ Anderson, OS RAS/Partitioning Project Lead
    SGI - Silicon Graphics Inc rja@sgi.com
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  4. Re: [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7

    On Thursday 24 July 2008 08:13, Russ Anderson wrote:
    > On Tue, Jul 22, 2008 at 12:42:10PM +1000, Nick Piggin wrote:
    > > On Saturday 19 July 2008 06:36, Russ Anderson wrote:
    > > > [PATCH 1/2] mm: Avoid putting a bad page back on the LRU v7
    > > >
    > > > Prevent a page with a physical memory error from being placed back
    > > > on the LRU. A new page flag (PG_memerror) is added if
    > > > CONFIG_PAGEFLAGS_EXTENDED is defined.
    > > >
    > > > Signed-off-by: Russ Anderson
    > > > Reviewed-by: Christoph Lameter
    > > >
    > > > ---
    > > > include/linux/page-flags.h | 18 ++++++++++++++++--
    > > > mm/migrate.c | 31 ++++++++++++++++++++++++++++++-
    > > > mm/page_alloc.c | 13 ++++++++-----
    > > > 3 files changed, 54 insertions(+), 8 deletions(-)
    > > >
    > > > Index: linux/mm/page_alloc.c
    > > > ================================================== =================
    > > > --- linux.orig/mm/page_alloc.c 2008-07-18 15:15:48.000000000 -0500
    > > > +++ linux/mm/page_alloc.c 2008-07-18 15:16:09.000000000 -0500
    > > > @@ -602,10 +602,10 @@ static int prep_new_page(struct page *pa
    > > > bad_page(page);
    > > >
    > > > /*
    > > > - * For now, we report if PG_reserved was found set, but do not
    > > > - * clear it, and do not allocate the page: as a safety net.
    > > > + * For now, we report if PG_reserved or PG_memerror was found set,
    > > > but + * do not clear it, and do not allocate the page: as a safety
    > > > net. */
    > > > - if (PageReserved(page))
    > > > + if (PageReserved(page) || PageMemError(page))
    > > > return 1;
    > > >
    > > > page->flags &= ~(1 << PG_uptodate | 1 << PG_error | 1 << PG_reclaim |
    > > > @@ -2475,8 +2475,11 @@ static void setup_zone_migrate_reserve(s
    > > > continue;
    > > > page = pfn_to_page(pfn);
    > > >
    > > > - /* Blocks with reserved pages will never free, skip them. */
    > > > - if (PageReserved(page))
    > > > + /*
    > > > + * Blocks with reserved pages or memory errors will never
    > > > + * free, skip them.
    > > > + */
    > > > + if (PageReserved(page) || PageMemError(page))
    > > > continue;
    > > >
    > > > block_migratetype = get_pageblock_migratetype(page);

    > >
    > > I don't like adding more branches like this into fastpaths like this. It
    > > would make a lot more sense to me if you just had some private module
    > > that does the job of isolating the page from the lru and/or elevating
    > > their refcount so that they do not get put back on freelists.

    >
    > That is how it works. If PageMemError is set the migration code
    > leaves the page with an elevated refcount. The PageMemError() check
    > was to avoid reallocating the page was an additional safty net.
    > I'll pull the checks.


    Ah, if it's that easy, great, then I have no problems with the patch.
    Note that I have no problems with putting a VM_BUG_ON(PageMemError())
    or something like that instead -- perhaps not quite the safty net you
    would like. But helpful for developers and testers, and it acts as a
    helpful little comment.

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