user/sven/linux.git/include/linux/mm.h, branch v4.1.9

mm: make page pfmemalloc check more robust

2015-09-29T17:26:06Z

commit 2f064f3485cd29633ad1b3cfb00cc519509a3d72 upstream. Commit c48a11c7ad26 ("netvm: propagate page->pfmemalloc to skb") added checks for page->pfmemalloc to __skb_fill_page_desc(): if (page->pfmemalloc && !page->mapping) skb->pfmemalloc = true; It assumes page->mapping == NULL implies that page->pfmemalloc can be trusted. However, __delete_from_page_cache() can set set page->mapping to NULL and leave page->index value alone. Due to being in union, a non-zero page->index will be interpreted as true page->pfmemalloc. So the assumption is invalid if the networking code can see such a page. And it seems it can. We have encountered this with a NFS over loopback setup when such a page is attached to a new skbuf. There is no copying going on in this case so the page confuses __skb_fill_page_desc which interprets the index as pfmemalloc flag and the network stack drops packets that have been allocated using the reserves unless they are to be queued on sockets handling the swapping which is the case here and that leads to hangs when the nfs client waits for a response from the server which has been dropped and thus never arrive. The struct page is already heavily packed so rather than finding another hole to put it in, let's do a trick instead. We can reuse the index again but define it to an impossible value (-1UL). This is the page index so it should never see the value that large. Replace all direct users of page->pfmemalloc by page_is_pfmemalloc which will hide this nastiness from unspoiled eyes. The information will get lost if somebody wants to use page->index obviously but that was the case before and the original code expected that the information should be persisted somewhere else if that is really needed (e.g. what SLAB and SLUB do). [akpm@linux-foundation.org: fix blooper in slub] Fixes: c48a11c7ad26 ("netvm: propagate page->pfmemalloc to skb") Signed-off-by: Michal Hocko Debugged-by: Vlastimil Babka Debugged-by: Jiri Bohac Cc: Eric Dumazet Cc: David Miller Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

Revert "mm: avoid tail page refcounting on non-THP compound pages"

2015-04-22T16:44:36Z

This reverts commit 8d63d99a5dfbdb997d12dd3c07b2070ca723db3b. It causes in VM mapping refcount errors: page:ffffea0010a15040 count:0 mapcount:1 mapping: (null) index:0x0 flags: 0x8000000000008014(referenced|dirty|tail) page dumped because: VM_BUG_ON_PAGE(page_mapcount(page) != 0) ------------[ cut here ]------------ kernel BUG at mm/swap.c:134! as reported by Borislav Petkov Reported-and-tested-by: Borislav Petkov Cc: Kirill A. Shutemov Cc: Hugh Dickins Cc: Andrea Arcangeli Cc: Andrew Morton Cc: linux-mm@kvack.org Signed-off-by: Linus Torvalds

mm: new pfn_mkwrite same as page_mkwrite for VM_PFNMAP

2015-04-15T23:35:20Z

This will allow FS that uses VM_PFNMAP | VM_MIXEDMAP (no page structs) to get notified when access is a write to a read-only PFN. This can happen if we mmap() a file then first mmap-read from it to page-in a read-only PFN, than we mmap-write to the same page. We need this functionality to fix a DAX bug, where in the scenario above we fail to set ctime/mtime though we modified the file. An xfstest is attached to this patchset that shows the failure and the fix. (A DAX patch will follow) This functionality is extra important for us, because upon dirtying of a pmem page we also want to RDMA the page to a remote cluster node. We define a new pfn_mkwrite and do not reuse page_mkwrite because 1 - The name ;-) 2 - But mainly because it would take a very long and tedious audit of all page_mkwrite functions of VM_MIXEDMAP/VM_PFNMAP users. To make sure they do not now CRASH. For example current DAX code (which this is for) would crash. If we would want to reuse page_mkwrite, We will need to first patch all users, so to not-crash-on-no-page. Then enable this patch. But even if I did that I would not sleep so well at night. Adding a new vector is the safest thing to do, and is not that expensive. an extra pointer at a static function vector per driver. Also the new vector is better for performance, because else we Will call all current Kernel vectors, so to: check-ha-no-page-do-nothing and return. No need to call it from do_shared_fault because do_wp_page is called to change pte permissions anyway. Signed-off-by: Yigal Korman Signed-off-by: Boaz Harrosh Acked-by: Kirill A. Shutemov Cc: Matthew Wilcox Cc: Jan Kara Cc: Hugh Dickins Cc: Mel Gorman Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: uninline and cleanup page-mapping related helpers

2015-04-15T23:35:19Z

Most-used page->mapping helper -- page_mapping() -- has already uninlined. Let's uninline also page_rmapping() and page_anon_vma(). It saves us depending on configuration around 400 bytes in text: text data bss dec hex filename 660318 99254 410000 1169572 11d8a4 mm/built-in.o-before 659854 99254 410000 1169108 11d6d4 mm/built-in.o I also tried to make code a bit more clean. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Kirill A. Shutemov Cc: Christoph Lameter Cc: Konstantin Khlebnikov Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

include/linux/mm.h: simplify flag check

2015-04-15T23:35:19Z

Flip the flag test so that it is the simplest. No functional change, just a small readability improvement: No code changed: # arch/x86/kernel/sys_x86_64.o: text data bss dec hex filename 1551 24 0 1575 627 sys_x86_64.o.before 1551 24 0 1575 627 sys_x86_64.o.after md5: 70708d1b1ad35cc891118a69dc1a63f9 sys_x86_64.o.before.asm 70708d1b1ad35cc891118a69dc1a63f9 sys_x86_64.o.after.asm Signed-off-by: Borislav Petkov Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: avoid tail page refcounting on non-THP compound pages

2015-04-15T23:35:17Z

THP uses tail page refcounting to be able to split huge pages at any time. Tail page refcounting is not needed for other users of compound pages and it's harmful because of overhead. We try to exclude non-THP pages from tail page refcounting using __compound_tail_refcounted() check. It excludes most common non-THP compound pages: SL*B and hugetlb, but it doesn't catch rest of __GFP_COMP users -- drivers. And it's not only about overhead. Drivers might want to use compound pages to get refcounting semantics suitable for mapping high-order pages to userspace. But tail page refcounting breaks it. Tail page refcounting uses ->_mapcount in tail pages to store GUP pins on them. It means GUP pins would affect page_mapcount() for tail pages. It's not a problem for THP, because it never maps tail pages. But unlike THP, drivers map parts of compound pages with PTEs and it makes page_mapcount() be called for tail pages. In particular, GUP pins would shift PSS up and affect /proc/kpagecount for such pages. But, I'm not aware about anything which can lead to crash or other serious misbehaviour. Since currently all THP pages are anonymous and all drivers pages are not, we can fix the __compound_tail_refcounted() check by requiring PageAnon() to enable tail page refcounting. Signed-off-by: Kirill A. Shutemov Acked-by: Hugh Dickins Cc: Andrea Arcangeli Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: consolidate all page-flags helpers in

2015-04-15T23:35:17Z

Currently we take a naive approach to page flags on compound pages - we set the flag on the page without consideration if the flag makes sense for tail page or for compound page in general. This patchset try to sort this out by defining per-flag policy on what need to be done if page-flag helper operate on compound page. The last patch in the patchset also sanitizes usege of page->mapping for tail pages. We don't define the meaning of page->mapping for tail pages. Currently it's always NULL, which can be inconsistent with head page and potentially lead to problems. For now I caught one case of illegal usage of page flags or ->mapping: sound subsystem allocates pages with __GFP_COMP and maps them with PTEs. It leads to setting dirty bit on tail pages and access to tail_page's ->mapping. I don't see any bad behaviour caused by this, but worth fixing anyway. This patchset makes more sense if you take my THP refcounting into account: we will see more compound pages mapped with PTEs and we need to define behaviour of flags on compound pages to avoid bugs. This patch (of 16): We have page-flags helper function declarations/definitions spread over several header files. Let's consolidate them in . Signed-off-by: Kirill A. Shutemov Cc: Andrea Arcangeli Acked-by: Hugh Dickins Cc: Dave Hansen Cc: Mel Gorman Cc: Rik van Riel Cc: Vlastimil Babka Cc: Christoph Lameter Cc: Naoya Horiguchi Cc: Steve Capper Cc: "Aneesh Kumar K.V" Cc: Johannes Weiner Cc: Michal Hocko Cc: Jerome Marchand Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: completely remove dumping per-cpu lists from show_mem()

2015-04-14T23:49:01Z

It seems nobody needs this. Signed-off-by: Konstantin Khlebnikov Cc: Michal Hocko Cc: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: hide per-cpu lists in output of show_mem()

2015-04-14T23:49:01Z

This makes show_mem() much less verbose on huge machines. Instead of huge and almost useless dump of counters for each per-zone per-cpu lists this patch prints the sum of these counters for each zone (free_pcp) and size of per-cpu list for current cpu (local_pcp). The filter flag SHOW_MEM_PERCPU_LISTS reverts to the old verbose mode. [akpm@linux-foundation.org: update show_free_areas comment] Signed-off-by: Konstantin Khlebnikov Acked-by: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

page_writeback: clean up mess around cancel_dirty_page()

2015-04-14T23:49:01Z

This patch replaces cancel_dirty_page() with a helper function account_page_cleaned() which only updates counters. It's called from truncate_complete_page() and from try_to_free_buffers() (hack for ext3). Page is locked in both cases, page-lock protects against concurrent dirtiers: see commit 2d6d7f982846 ("mm: protect set_page_dirty() from ongoing truncation"). Delete_from_page_cache() shouldn't be called for dirty pages, they must be handled by caller (either written or truncated). This patch treats final dirty accounting fixup at the end of __delete_from_page_cache() as a debug check and adds WARN_ON_ONCE() around it. If something removes dirty pages without proper handling that might be a bug and unwritten data might be lost. Hugetlbfs has no dirty pages accounting, ClearPageDirty() is enough here. cancel_dirty_page() in nfs_wb_page_cancel() is redundant. This is helper for nfs_invalidate_page() and it's called only in case complete invalidation. The mess was started in v2.6.20 after commits 46d2277c796f ("Clean up and make try_to_free_buffers() not race with dirty pages") and 3e67c0987d75 ("truncate: clear page dirtiness before running try_to_free_buffers()") first was reverted right in v2.6.20 in commit ecdfc9787fe5 ("Resurrect 'try_to_free_buffers()' VM hackery"), second in v2.6.25 commit a2b345642f53 ("Fix dirty page accounting leak with ext3 data=journal"). Custom fixes were introduced between these points. NFS in v2.6.23, commit 1b3b4a1a2deb ("NFS: Fix a write request leak in nfs_invalidate_page()"). Kludge in __delete_from_page_cache() in v2.6.24, commit 3a6927906f1b ("Do dirty page accounting when removing a page from the page cache"). Since v2.6.25 all of them are redundant. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Konstantin Khlebnikov Cc: Tejun Heo Cc: Jan Kara Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds