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    SubjectRe: [PATCH] [13/16] POISON: The high level memory error handler in the VM
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    On Tue, 2009-04-07 at 17:10 +0200, Andi Kleen wrote:
    > This patch adds the high level memory handler that poisons pages.
    > It is portable code and lives in mm/memory-failure.c

    I think this is an important feature, thanks for doing all this work
    Andi.

    > Index: linux/mm/memory-failure.c
    > ===================================================================
    > --- /dev/null 1970-01-01 00:00:00.000000000 +0000
    > +++ linux/mm/memory-failure.c 2009-04-07 16:39:39.000000000 +0200
    > +
    > +/*
    > + * Clean (or cleaned) page cache page.
    > + */
    > +static int me_pagecache_clean(struct page *p)
    > +{
    > + struct address_space *mapping;
    > +
    > + if (PagePrivate(p))
    > + do_invalidatepage(p, 0);
    > + mapping = page_mapping(p);
    > + if (mapping) {
    > + if (!remove_mapping(mapping, p))
    > + return FAILED;
    > + }
    > + return RECOVERED;
    > +}
    > +
    > +/*
    > + * Dirty cache page page
    > + * Issues: when the error hit a hole page the error is not properly
    > + * propagated.
    > + */
    > +static int me_pagecache_dirty(struct page *p)
    > +{
    > + struct address_space *mapping = page_mapping(p);
    > +
    > + SetPageError(p);
    > + /* TBD: print more information about the file. */
    > + printk(KERN_ERR "MCE: Hardware memory corruption on dirty file page: write error\n");
    > + if (mapping) {
    > + /* CHECKME: does that report the error in all cases? */
    > + mapping_set_error(mapping, EIO);
    > + }
    > + if (PagePrivate(p)) {
    > + if (try_to_release_page(p, GFP_KERNEL)) {

    So, try_to_release_page returns 1 when it works. I know this only
    because I have to read it every time to remember ;)

    try_to_release_page is also very likely to fail if the page is dirty or
    under writeback. At the end of the day, we'll probably need a call into
    the FS to tell it a given page isn't coming back, and to clean it at all
    cost.

    invalidatepage is close, but ext3/reiserfs will keep the buffer heads
    and let the page->mapping go to null in an ugly data=ordered corner
    case. The buffer heads pin the page and it won't be freed until the IO
    is done.

    -chris




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