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author | Hugh Dickins <hugh@veritas.com> | 2006-02-14 13:52:58 -0800 |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-02-14 16:09:33 -0800 |
commit | 41d78ba55037468e6c86c53e3076d1a74841de39 (patch) | |
tree | d970f18d18532009b17c736583429401dbd64ade /ipc | |
parent | 7277232374680595cdbc774fd246b206f56db015 (diff) | |
download | linux-41d78ba55037468e6c86c53e3076d1a74841de39.tar.bz2 |
[PATCH] compound page: use page[1].lru
If a compound page has its own put_page_testzero destructor (the only current
example is free_huge_page), that is noted in page[1].mapping of the compound
page. But that's rather a poor place to keep it: functions which call
set_page_dirty_lock after get_user_pages (e.g. Infiniband's
__ib_umem_release) ought to be checking first, otherwise set_page_dirty is
liable to crash on what's not the address of a struct address_space.
And now I'm about to make that worse: it turns out that every compound page
needs a destructor, so we can no longer rely on hugetlb pages going their own
special way, to avoid further problems of page->mapping reuse. For example,
not many people know that: on 50% of i386 -Os builds, the first tail page of a
compound page purports to be PageAnon (when its destructor has an odd
address), which surprises page_add_file_rmap.
Keep the compound page destructor in page[1].lru.next instead. And to free up
the common pairing of mapping and index, also move compound page order from
index to lru.prev. Slab reuses page->lru too: but if we ever need slab to use
compound pages, it can easily stack its use above this.
(akpm: decoded version of the above: the tail pages of a compound page now
have ->mapping==NULL, so there's no need for the set_page_dirty[_lock]()
caller to check that they're not compund pages before doing the dirty).
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'ipc')
0 files changed, 0 insertions, 0 deletions