user/sven/linux.git/include/linux/mm.h, branch v3.18.22

vm: add VM_FAULT_SIGSEGV handling support

2015-02-06T06:36:01Z

commit 33692f27597fcab536d7cbbcc8f52905133e4aa7 upstream. The core VM already knows about VM_FAULT_SIGBUS, but cannot return a "you should SIGSEGV" error, because the SIGSEGV case was generally handled by the caller - usually the architecture fault handler. That results in lots of duplication - all the architecture fault handlers end up doing very similar "look up vma, check permissions, do retries etc" - but it generally works. However, there are cases where the VM actually wants to SIGSEGV, and applications _expect_ SIGSEGV. In particular, when accessing the stack guard page, libsigsegv expects a SIGSEGV. And it usually got one, because the stack growth is handled by that duplicated architecture fault handler. However, when the generic VM layer started propagating the error return from the stack expansion in commit fee7e49d4514 ("mm: propagate error from stack expansion even for guard page"), that now exposed the existing VM_FAULT_SIGBUS result to user space. And user space really expected SIGSEGV, not SIGBUS. To fix that case, we need to add a VM_FAULT_SIGSEGV, and teach all those duplicate architecture fault handlers about it. They all already have the code to handle SIGSEGV, so it's about just tying that new return value to the existing code, but it's all a bit annoying. This is the mindless minimal patch to do this. A more extensive patch would be to try to gather up the mostly shared fault handling logic into one generic helper routine, and long-term we really should do that cleanup. Just from this patch, you can generally see that most architectures just copied (directly or indirectly) the old x86 way of doing things, but in the meantime that original x86 model has been improved to hold the VM semaphore for shorter times etc and to handle VM_FAULT_RETRY and other "newer" things, so it would be a good idea to bring all those improvements to the generic case and teach other architectures about them too. Reported-and-tested-by: Takashi Iwai Tested-by: Jan Engelhardt Acked-by: Heiko Carstens # "s390 still compiles and boots" Cc: linux-arch@vger.kernel.org Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: propagate error from stack expansion even for guard page

2015-01-16T14:59:57Z

commit fee7e49d45149fba60156f5b59014f764d3e3728 upstream. Jay Foad reports that the address sanitizer test (asan) sometimes gets confused by a stack pointer that ends up being outside the stack vma that is reported by /proc/maps. This happens due to an interaction between RLIMIT_STACK and the guard page: when we do the guard page check, we ignore the potential error from the stack expansion, which effectively results in a missing guard page, since the expected stack expansion won't have been done. And since /proc/maps explicitly ignores the guard page (commit d7824370e263: "mm: fix up some user-visible effects of the stack guard page"), the stack pointer ends up being outside the reported stack area. This is the minimal patch: it just propagates the error. It also effectively makes the guard page part of the stack limit, which in turn measn that the actual real stack is one page less than the stack limit. Let's see if anybody notices. We could teach acct_stack_growth() to allow an extra page for a grow-up/grow-down stack in the rlimit test, but I don't want to add more complexity if it isn't needed. Reported-and-tested-by: Jay Foad Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman

mm: page-writeback: inline account_page_dirtied() into single caller

2014-10-29T23:33:14Z

A follow-up patch would have changed the call signature. To save the trouble, just fold it instead. Signed-off-by: Johannes Weiner Acked-by: Michal Hocko Cc: Vladimir Davydov Cc: [3.17.x] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

Merge tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4

2014-10-20T16:50:11Z

Pull ext4 updates from Ted Ts'o: "A large number of cleanups and bug fixes, with some (minor) journal optimizations" [ This got sent to me before -rc1, but was stuck in my spam folder. - Linus ] * tag 'ext4_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4: (67 commits) ext4: check s_chksum_driver when looking for bg csum presence ext4: move error report out of atomic context in ext4_init_block_bitmap() ext4: Replace open coded mdata csum feature to helper function ext4: delete useless comments about ext4_move_extents ext4: fix reservation overflow in ext4_da_write_begin ext4: add ext4_iget_normal() which is to be used for dir tree lookups ext4: don't orphan or truncate the boot loader inode ext4: grab missed write_count for EXT4_IOC_SWAP_BOOT ext4: optimize block allocation on grow indepth ext4: get rid of code duplication ext4: fix over-defensive complaint after journal abort ext4: fix return value of ext4_do_update_inode ext4: fix mmap data corruption when blocksize < pagesize vfs: fix data corruption when blocksize < pagesize for mmaped data ext4: fold ext4_nojournal_sops into ext4_sops ext4: support freezing ext2 (nojournal) file systems ext4: fold ext4_sync_fs_nojournal() into ext4_sync_fs() ext4: don't check quota format when there are no quota files jbd2: simplify calling convention around __jbd2_journal_clean_checkpoint_list jbd2: avoid pointless scanning of checkpoint lists ...

mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared

2014-10-14T00:18:28Z

For VMAs that don't want write notifications, PTEs created for read faults have their write bit set. If the read fault happens after VM_SOFTDIRTY is cleared, then the PTE's softdirty bit will remain clear after subsequent writes. Here's a simple code snippet to demonstrate the bug: char* m = mmap(NULL, getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_SHARED, -1, 0); system("echo 4 > /proc/$PPID/clear_refs"); /* clear VM_SOFTDIRTY */ assert(*m == '\0'); /* new PTE allows write access */ assert(!soft_dirty(x)); *m = 'x'; /* should dirty the page */ assert(soft_dirty(x)); /* fails */ With this patch, write notifications are enabled when VM_SOFTDIRTY is cleared. Furthermore, to avoid unnecessary faults, write notifications are disabled when VM_SOFTDIRTY is set. As a side effect of enabling and disabling write notifications with care, this patch fixes a bug in mprotect where vm_page_prot bits set by drivers were zapped on mprotect. An analogous bug was fixed in mmap by commit c9d0bf241451 ("mm: uncached vma support with writenotify"). Signed-off-by: Peter Feiner Reported-by: Peter Feiner Suggested-by: Kirill A. Shutemov Cc: Cyrill Gorcunov Cc: Pavel Emelyanov Cc: Jamie Liu Cc: Hugh Dickins Cc: Naoya Horiguchi Cc: Bjorn Helgaas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

x86: optimize resource lookups for ioremap

2014-10-14T00:18:22Z

We have a large university system in the UK that is experiencing very long delays modprobing the driver for a specific I/O device. The delay is from 8-10 minutes per device and there are 31 devices in the system. This 4 to 5 hour delay in starting up those I/O devices is very much a burden on the customer. There are two causes for requiring a restart/reload of the drivers. First is periodic preventive maintenance (PM) and the second is if any of the devices experience a fatal error. Both of these trigger this excessively long delay in bringing the system back up to full capability. The problem was tracked down to a very slow IOREMAP operation and the excessively long ioresource lookup to insure that the user is not attempting to ioremap RAM. These patches provide a speed up to that function. The modprobe time appears to be affected quite a bit by previous activity on the ioresource list, which I suspect is due to cache preloading. While the overall improvement is impacted by other overhead of starting the devices, this drastically improves the modprobe time. Also our system is considerably smaller so the percentages gained will not be the same. Best case improvement with the modprobe on our 20 device smallish system was from 'real 5m51.913s' to 'real 0m18.275s'. This patch (of 2): Since the ioremap operation is verifying that the specified address range is NOT RAM, it will search the entire ioresource list if the condition is true. To make matters worse, it does this one 4k page at a time. For a 128M BAR region this is 32 passes to determine the entire region does not contain any RAM addresses. This patch provides another resource lookup function, region_is_ram, that searches for the entire region specified, verifying that it is completely contained within the resource region. If it is found, then it is checked to be RAM or not, within a single pass. The return result reflects if it was found or not (-1), and whether it is RAM (1) or not (0). This allows the caller to fallback to the previous page by page search if it was not found. [akpm@linux-foundation.org: fix spellos and typos in comment] Signed-off-by: Mike Travis Acked-by: Alex Thorlton Reviewed-by: Cliff Wickman Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Mark Salter Cc: Dave Young Cc: Rik van Riel Cc: Peter Zijlstra Cc: Mel Gorman Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm/balloon_compaction: redesign ballooned pages management

2014-10-10T02:26:01Z

Sasha Levin reported KASAN splash inside isolate_migratepages_range(). Problem is in the function __is_movable_balloon_page() which tests AS_BALLOON_MAP in page->mapping->flags. This function has no protection against anonymous pages. As result it tried to check address space flags inside struct anon_vma. Further investigation shows more problems in current implementation: * Special branch in __unmap_and_move() never works: balloon_page_movable() checks page flags and page_count. In __unmap_and_move() page is locked, reference counter is elevated, thus balloon_page_movable() always fails. As a result execution goes to the normal migration path. virtballoon_migratepage() returns MIGRATEPAGE_BALLOON_SUCCESS instead of MIGRATEPAGE_SUCCESS, move_to_new_page() thinks this is an error code and assigns newpage->mapping to NULL. Newly migrated page lose connectivity with balloon an all ability for further migration. * lru_lock erroneously required in isolate_migratepages_range() for isolation ballooned page. This function releases lru_lock periodically, this makes migration mostly impossible for some pages. * balloon_page_dequeue have a tight race with balloon_page_isolate: balloon_page_isolate could be executed in parallel with dequeue between picking page from list and locking page_lock. Race is rare because they use trylock_page() for locking. This patch fixes all of them. Instead of fake mapping with special flag this patch uses special state of page->_mapcount: PAGE_BALLOON_MAPCOUNT_VALUE = -256. Buddy allocator uses PAGE_BUDDY_MAPCOUNT_VALUE = -128 for similar purpose. Storing mark directly in struct page makes everything safer and easier. PagePrivate is used to mark pages present in page list (i.e. not isolated, like PageLRU for normal pages). It replaces special rules for reference counter and makes balloon migration similar to migration of normal pages. This flag is protected by page_lock together with link to the balloon device. Signed-off-by: Konstantin Khlebnikov Reported-by: Sasha Levin Link: http://lkml.kernel.org/p/53E6CEAA.9020105@oracle.com Cc: Rafael Aquini Cc: Andrey Ryabinin Cc: [3.8+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

mm: introduce check_data_rlimit helper

2014-10-10T02:25:55Z

To eliminate code duplication lets introduce check_data_rlimit helper which we will use in brk() and prctl() syscalls. Signed-off-by: Cyrill Gorcunov Cc: Kees Cook Cc: Tejun Heo Cc: Andrew Vagin Cc: Eric W. Biederman Cc: H. Peter Anvin Acked-by: Serge Hallyn Cc: Pavel Emelyanov Cc: Vasiliy Kulikov Cc: KAMEZAWA Hiroyuki Cc: Michael Kerrisk Cc: Julien Tinnes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

proc/maps: make vm_is_stack() logic namespace-friendly

2014-10-10T02:25:50Z

- Rename vm_is_stack() to task_of_stack() and change it to return "struct task_struct *" rather than the global (and thus wrong in general) pid_t. - Add the new pid_of_stack() helper which calls task_of_stack() and uses the right namespace to report the correct pid_t. Unfortunately we need to define this helper twice, in task_mmu.c and in task_nommu.c. perhaps it makes sense to add fs/proc/util.c and move at least pid_of_stack/task_of_stack there to avoid the code duplication. - Change show_map_vma() and show_numa_map() to use the new helper. Signed-off-by: Oleg Nesterov Cc: Alexander Viro Cc: Cyrill Gorcunov Cc: "Eric W. Biederman" Cc: Greg Ungerer Cc: "Kirill A. Shutemov" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

vfs: fix data corruption when blocksize < pagesize for mmaped data

2014-10-02T01:49:18Z

->page_mkwrite() is used by filesystems to allocate blocks under a page which is becoming writeably mmapped in some process' address space. This allows a filesystem to return a page fault if there is not enough space available, user exceeds quota or similar problem happens, rather than silently discarding data later when writepage is called. However VFS fails to call ->page_mkwrite() in all the cases where filesystems need it when blocksize < pagesize. For example when blocksize = 1024, pagesize = 4096 the following is problematic: ftruncate(fd, 0); pwrite(fd, buf, 1024, 0); map = mmap(NULL, 1024, PROT_WRITE, MAP_SHARED, fd, 0); map[0] = 'a'; ----> page_mkwrite() for index 0 is called ftruncate(fd, 10000); /* or even pwrite(fd, buf, 1, 10000) */ mremap(map, 1024, 10000, 0); map[4095] = 'a'; ----> no page_mkwrite() called At the moment ->page_mkwrite() is called, filesystem can allocate only one block for the page because i_size == 1024. Otherwise it would create blocks beyond i_size which is generally undesirable. But later at ->writepage() time, we also need to store data at offset 4095 but we don't have block allocated for it. This patch introduces a helper function filesystems can use to have ->page_mkwrite() called at all the necessary moments. Signed-off-by: Jan Kara Signed-off-by: Theodore Ts'o Cc: stable@vger.kernel.org