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authorFathi Boudra <fathi.boudra@linaro.org>2013-04-28 09:33:08 +0300
committerFathi Boudra <fathi.boudra@linaro.org>2013-04-28 09:33:08 +0300
commit3b4bd47f8f4ed3aaf7c81c9b5d2d37ad79fadf4a (patch)
treeb9996006addfd7ae70a39672b76843b49aebc189 /mm/mlock.c
downloadlinux-linaro-highbank-3b4bd47f8f4ed3aaf7c81c9b5d2d37ad79fadf4a.tar.gz
Imported Upstream version 3.9.0HEADupstream/3.9.0upstreammaster
Diffstat (limited to 'mm/mlock.c')
-rw-r--r--mm/mlock.c590
1 files changed, 590 insertions, 0 deletions
diff --git a/mm/mlock.c b/mm/mlock.c
new file mode 100644
index 00000000..1c5e33fc
--- /dev/null
+++ b/mm/mlock.c
@@ -0,0 +1,590 @@
+/*
+ * linux/mm/mlock.c
+ *
+ * (C) Copyright 1995 Linus Torvalds
+ * (C) Copyright 2002 Christoph Hellwig
+ */
+
+#include <linux/capability.h>
+#include <linux/mman.h>
+#include <linux/mm.h>
+#include <linux/swap.h>
+#include <linux/swapops.h>
+#include <linux/pagemap.h>
+#include <linux/mempolicy.h>
+#include <linux/syscalls.h>
+#include <linux/sched.h>
+#include <linux/export.h>
+#include <linux/rmap.h>
+#include <linux/mmzone.h>
+#include <linux/hugetlb.h>
+
+#include "internal.h"
+
+int can_do_mlock(void)
+{
+ if (capable(CAP_IPC_LOCK))
+ return 1;
+ if (rlimit(RLIMIT_MEMLOCK) != 0)
+ return 1;
+ return 0;
+}
+EXPORT_SYMBOL(can_do_mlock);
+
+/*
+ * Mlocked pages are marked with PageMlocked() flag for efficient testing
+ * in vmscan and, possibly, the fault path; and to support semi-accurate
+ * statistics.
+ *
+ * An mlocked page [PageMlocked(page)] is unevictable. As such, it will
+ * be placed on the LRU "unevictable" list, rather than the [in]active lists.
+ * The unevictable list is an LRU sibling list to the [in]active lists.
+ * PageUnevictable is set to indicate the unevictable state.
+ *
+ * When lazy mlocking via vmscan, it is important to ensure that the
+ * vma's VM_LOCKED status is not concurrently being modified, otherwise we
+ * may have mlocked a page that is being munlocked. So lazy mlock must take
+ * the mmap_sem for read, and verify that the vma really is locked
+ * (see mm/rmap.c).
+ */
+
+/*
+ * LRU accounting for clear_page_mlock()
+ */
+void clear_page_mlock(struct page *page)
+{
+ if (!TestClearPageMlocked(page))
+ return;
+
+ mod_zone_page_state(page_zone(page), NR_MLOCK,
+ -hpage_nr_pages(page));
+ count_vm_event(UNEVICTABLE_PGCLEARED);
+ if (!isolate_lru_page(page)) {
+ putback_lru_page(page);
+ } else {
+ /*
+ * We lost the race. the page already moved to evictable list.
+ */
+ if (PageUnevictable(page))
+ count_vm_event(UNEVICTABLE_PGSTRANDED);
+ }
+}
+
+/*
+ * Mark page as mlocked if not already.
+ * If page on LRU, isolate and putback to move to unevictable list.
+ */
+void mlock_vma_page(struct page *page)
+{
+ BUG_ON(!PageLocked(page));
+
+ if (!TestSetPageMlocked(page)) {
+ mod_zone_page_state(page_zone(page), NR_MLOCK,
+ hpage_nr_pages(page));
+ count_vm_event(UNEVICTABLE_PGMLOCKED);
+ if (!isolate_lru_page(page))
+ putback_lru_page(page);
+ }
+}
+
+/**
+ * munlock_vma_page - munlock a vma page
+ * @page - page to be unlocked
+ *
+ * called from munlock()/munmap() path with page supposedly on the LRU.
+ * When we munlock a page, because the vma where we found the page is being
+ * munlock()ed or munmap()ed, we want to check whether other vmas hold the
+ * page locked so that we can leave it on the unevictable lru list and not
+ * bother vmscan with it. However, to walk the page's rmap list in
+ * try_to_munlock() we must isolate the page from the LRU. If some other
+ * task has removed the page from the LRU, we won't be able to do that.
+ * So we clear the PageMlocked as we might not get another chance. If we
+ * can't isolate the page, we leave it for putback_lru_page() and vmscan
+ * [page_referenced()/try_to_unmap()] to deal with.
+ */
+unsigned int munlock_vma_page(struct page *page)
+{
+ unsigned int page_mask = 0;
+
+ BUG_ON(!PageLocked(page));
+
+ if (TestClearPageMlocked(page)) {
+ unsigned int nr_pages = hpage_nr_pages(page);
+ mod_zone_page_state(page_zone(page), NR_MLOCK, -nr_pages);
+ page_mask = nr_pages - 1;
+ if (!isolate_lru_page(page)) {
+ int ret = SWAP_AGAIN;
+
+ /*
+ * Optimization: if the page was mapped just once,
+ * that's our mapping and we don't need to check all the
+ * other vmas.
+ */
+ if (page_mapcount(page) > 1)
+ ret = try_to_munlock(page);
+ /*
+ * did try_to_unlock() succeed or punt?
+ */
+ if (ret != SWAP_MLOCK)
+ count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+
+ putback_lru_page(page);
+ } else {
+ /*
+ * Some other task has removed the page from the LRU.
+ * putback_lru_page() will take care of removing the
+ * page from the unevictable list, if necessary.
+ * vmscan [page_referenced()] will move the page back
+ * to the unevictable list if some other vma has it
+ * mlocked.
+ */
+ if (PageUnevictable(page))
+ count_vm_event(UNEVICTABLE_PGSTRANDED);
+ else
+ count_vm_event(UNEVICTABLE_PGMUNLOCKED);
+ }
+ }
+
+ return page_mask;
+}
+
+/**
+ * __mlock_vma_pages_range() - mlock a range of pages in the vma.
+ * @vma: target vma
+ * @start: start address
+ * @end: end address
+ *
+ * This takes care of making the pages present too.
+ *
+ * return 0 on success, negative error code on error.
+ *
+ * vma->vm_mm->mmap_sem must be held for at least read.
+ */
+long __mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end, int *nonblocking)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ unsigned long nr_pages = (end - start) / PAGE_SIZE;
+ int gup_flags;
+
+ VM_BUG_ON(start & ~PAGE_MASK);
+ VM_BUG_ON(end & ~PAGE_MASK);
+ VM_BUG_ON(start < vma->vm_start);
+ VM_BUG_ON(end > vma->vm_end);
+ VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));
+
+ gup_flags = FOLL_TOUCH | FOLL_MLOCK;
+ /*
+ * We want to touch writable mappings with a write fault in order
+ * to break COW, except for shared mappings because these don't COW
+ * and we would not want to dirty them for nothing.
+ */
+ if ((vma->vm_flags & (VM_WRITE | VM_SHARED)) == VM_WRITE)
+ gup_flags |= FOLL_WRITE;
+
+ /*
+ * We want mlock to succeed for regions that have any permissions
+ * other than PROT_NONE.
+ */
+ if (vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))
+ gup_flags |= FOLL_FORCE;
+
+ /*
+ * We made sure addr is within a VMA, so the following will
+ * not result in a stack expansion that recurses back here.
+ */
+ return __get_user_pages(current, mm, start, nr_pages, gup_flags,
+ NULL, NULL, nonblocking);
+}
+
+/*
+ * convert get_user_pages() return value to posix mlock() error
+ */
+static int __mlock_posix_error_return(long retval)
+{
+ if (retval == -EFAULT)
+ retval = -ENOMEM;
+ else if (retval == -ENOMEM)
+ retval = -EAGAIN;
+ return retval;
+}
+
+/*
+ * munlock_vma_pages_range() - munlock all pages in the vma range.'
+ * @vma - vma containing range to be munlock()ed.
+ * @start - start address in @vma of the range
+ * @end - end of range in @vma.
+ *
+ * For mremap(), munmap() and exit().
+ *
+ * Called with @vma VM_LOCKED.
+ *
+ * Returns with VM_LOCKED cleared. Callers must be prepared to
+ * deal with this.
+ *
+ * We don't save and restore VM_LOCKED here because pages are
+ * still on lru. In unmap path, pages might be scanned by reclaim
+ * and re-mlocked by try_to_{munlock|unmap} before we unmap and
+ * free them. This will result in freeing mlocked pages.
+ */
+void munlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
+{
+ vma->vm_flags &= ~VM_LOCKED;
+
+ while (start < end) {
+ struct page *page;
+ unsigned int page_mask, page_increm;
+
+ /*
+ * Although FOLL_DUMP is intended for get_dump_page(),
+ * it just so happens that its special treatment of the
+ * ZERO_PAGE (returning an error instead of doing get_page)
+ * suits munlock very well (and if somehow an abnormal page
+ * has sneaked into the range, we won't oops here: great).
+ */
+ page = follow_page_mask(vma, start, FOLL_GET | FOLL_DUMP,
+ &page_mask);
+ if (page && !IS_ERR(page)) {
+ lock_page(page);
+ lru_add_drain();
+ /*
+ * Any THP page found by follow_page_mask() may have
+ * gotten split before reaching munlock_vma_page(),
+ * so we need to recompute the page_mask here.
+ */
+ page_mask = munlock_vma_page(page);
+ unlock_page(page);
+ put_page(page);
+ }
+ page_increm = 1 + (~(start >> PAGE_SHIFT) & page_mask);
+ start += page_increm * PAGE_SIZE;
+ cond_resched();
+ }
+}
+
+/*
+ * mlock_fixup - handle mlock[all]/munlock[all] requests.
+ *
+ * Filters out "special" vmas -- VM_LOCKED never gets set for these, and
+ * munlock is a no-op. However, for some special vmas, we go ahead and
+ * populate the ptes.
+ *
+ * For vmas that pass the filters, merge/split as appropriate.
+ */
+static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
+ unsigned long start, unsigned long end, vm_flags_t newflags)
+{
+ struct mm_struct *mm = vma->vm_mm;
+ pgoff_t pgoff;
+ int nr_pages;
+ int ret = 0;
+ int lock = !!(newflags & VM_LOCKED);
+
+ if (newflags == vma->vm_flags || (vma->vm_flags & VM_SPECIAL) ||
+ is_vm_hugetlb_page(vma) || vma == get_gate_vma(current->mm))
+ goto out; /* don't set VM_LOCKED, don't count */
+
+ pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
+ *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
+ vma->vm_file, pgoff, vma_policy(vma));
+ if (*prev) {
+ vma = *prev;
+ goto success;
+ }
+
+ if (start != vma->vm_start) {
+ ret = split_vma(mm, vma, start, 1);
+ if (ret)
+ goto out;
+ }
+
+ if (end != vma->vm_end) {
+ ret = split_vma(mm, vma, end, 0);
+ if (ret)
+ goto out;
+ }
+
+success:
+ /*
+ * Keep track of amount of locked VM.
+ */
+ nr_pages = (end - start) >> PAGE_SHIFT;
+ if (!lock)
+ nr_pages = -nr_pages;
+ mm->locked_vm += nr_pages;
+
+ /*
+ * vm_flags is protected by the mmap_sem held in write mode.
+ * It's okay if try_to_unmap_one unmaps a page just after we
+ * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
+ */
+
+ if (lock)
+ vma->vm_flags = newflags;
+ else
+ munlock_vma_pages_range(vma, start, end);
+
+out:
+ *prev = vma;
+ return ret;
+}
+
+static int do_mlock(unsigned long start, size_t len, int on)
+{
+ unsigned long nstart, end, tmp;
+ struct vm_area_struct * vma, * prev;
+ int error;
+
+ VM_BUG_ON(start & ~PAGE_MASK);
+ VM_BUG_ON(len != PAGE_ALIGN(len));
+ end = start + len;
+ if (end < start)
+ return -EINVAL;
+ if (end == start)
+ return 0;
+ vma = find_vma(current->mm, start);
+ if (!vma || vma->vm_start > start)
+ return -ENOMEM;
+
+ prev = vma->vm_prev;
+ if (start > vma->vm_start)
+ prev = vma;
+
+ for (nstart = start ; ; ) {
+ vm_flags_t newflags;
+
+ /* Here we know that vma->vm_start <= nstart < vma->vm_end. */
+
+ newflags = vma->vm_flags & ~VM_LOCKED;
+ if (on)
+ newflags |= VM_LOCKED | VM_POPULATE;
+
+ tmp = vma->vm_end;
+ if (tmp > end)
+ tmp = end;
+ error = mlock_fixup(vma, &prev, nstart, tmp, newflags);
+ if (error)
+ break;
+ nstart = tmp;
+ if (nstart < prev->vm_end)
+ nstart = prev->vm_end;
+ if (nstart >= end)
+ break;
+
+ vma = prev->vm_next;
+ if (!vma || vma->vm_start != nstart) {
+ error = -ENOMEM;
+ break;
+ }
+ }
+ return error;
+}
+
+/*
+ * __mm_populate - populate and/or mlock pages within a range of address space.
+ *
+ * This is used to implement mlock() and the MAP_POPULATE / MAP_LOCKED mmap
+ * flags. VMAs must be already marked with the desired vm_flags, and
+ * mmap_sem must not be held.
+ */
+int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
+{
+ struct mm_struct *mm = current->mm;
+ unsigned long end, nstart, nend;
+ struct vm_area_struct *vma = NULL;
+ int locked = 0;
+ long ret = 0;
+
+ VM_BUG_ON(start & ~PAGE_MASK);
+ VM_BUG_ON(len != PAGE_ALIGN(len));
+ end = start + len;
+
+ for (nstart = start; nstart < end; nstart = nend) {
+ /*
+ * We want to fault in pages for [nstart; end) address range.
+ * Find first corresponding VMA.
+ */
+ if (!locked) {
+ locked = 1;
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, nstart);
+ } else if (nstart >= vma->vm_end)
+ vma = vma->vm_next;
+ if (!vma || vma->vm_start >= end)
+ break;
+ /*
+ * Set [nstart; nend) to intersection of desired address
+ * range with the first VMA. Also, skip undesirable VMA types.
+ */
+ nend = min(end, vma->vm_end);
+ if ((vma->vm_flags & (VM_IO | VM_PFNMAP | VM_POPULATE)) !=
+ VM_POPULATE)
+ continue;
+ if (nstart < vma->vm_start)
+ nstart = vma->vm_start;
+ /*
+ * Now fault in a range of pages. __mlock_vma_pages_range()
+ * double checks the vma flags, so that it won't mlock pages
+ * if the vma was already munlocked.
+ */
+ ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
+ if (ret < 0) {
+ if (ignore_errors) {
+ ret = 0;
+ continue; /* continue at next VMA */
+ }
+ ret = __mlock_posix_error_return(ret);
+ break;
+ }
+ nend = nstart + ret * PAGE_SIZE;
+ ret = 0;
+ }
+ if (locked)
+ up_read(&mm->mmap_sem);
+ return ret; /* 0 or negative error code */
+}
+
+SYSCALL_DEFINE2(mlock, unsigned long, start, size_t, len)
+{
+ unsigned long locked;
+ unsigned long lock_limit;
+ int error = -ENOMEM;
+
+ if (!can_do_mlock())
+ return -EPERM;
+
+ lru_add_drain_all(); /* flush pagevec */
+
+ down_write(&current->mm->mmap_sem);
+ len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
+ start &= PAGE_MASK;
+
+ locked = len >> PAGE_SHIFT;
+ locked += current->mm->locked_vm;
+
+ lock_limit = rlimit(RLIMIT_MEMLOCK);
+ lock_limit >>= PAGE_SHIFT;
+
+ /* check against resource limits */
+ if ((locked <= lock_limit) || capable(CAP_IPC_LOCK))
+ error = do_mlock(start, len, 1);
+ up_write(&current->mm->mmap_sem);
+ if (!error)
+ error = __mm_populate(start, len, 0);
+ return error;
+}
+
+SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
+{
+ int ret;
+
+ down_write(&current->mm->mmap_sem);
+ len = PAGE_ALIGN(len + (start & ~PAGE_MASK));
+ start &= PAGE_MASK;
+ ret = do_mlock(start, len, 0);
+ up_write(&current->mm->mmap_sem);
+ return ret;
+}
+
+static int do_mlockall(int flags)
+{
+ struct vm_area_struct * vma, * prev = NULL;
+
+ if (flags & MCL_FUTURE)
+ current->mm->def_flags |= VM_LOCKED | VM_POPULATE;
+ else
+ current->mm->def_flags &= ~(VM_LOCKED | VM_POPULATE);
+ if (flags == MCL_FUTURE)
+ goto out;
+
+ for (vma = current->mm->mmap; vma ; vma = prev->vm_next) {
+ vm_flags_t newflags;
+
+ newflags = vma->vm_flags & ~VM_LOCKED;
+ if (flags & MCL_CURRENT)
+ newflags |= VM_LOCKED | VM_POPULATE;
+
+ /* Ignore errors */
+ mlock_fixup(vma, &prev, vma->vm_start, vma->vm_end, newflags);
+ }
+out:
+ return 0;
+}
+
+SYSCALL_DEFINE1(mlockall, int, flags)
+{
+ unsigned long lock_limit;
+ int ret = -EINVAL;
+
+ if (!flags || (flags & ~(MCL_CURRENT | MCL_FUTURE)))
+ goto out;
+
+ ret = -EPERM;
+ if (!can_do_mlock())
+ goto out;
+
+ if (flags & MCL_CURRENT)
+ lru_add_drain_all(); /* flush pagevec */
+
+ down_write(&current->mm->mmap_sem);
+
+ lock_limit = rlimit(RLIMIT_MEMLOCK);
+ lock_limit >>= PAGE_SHIFT;
+
+ ret = -ENOMEM;
+ if (!(flags & MCL_CURRENT) || (current->mm->total_vm <= lock_limit) ||
+ capable(CAP_IPC_LOCK))
+ ret = do_mlockall(flags);
+ up_write(&current->mm->mmap_sem);
+ if (!ret && (flags & MCL_CURRENT))
+ mm_populate(0, TASK_SIZE);
+out:
+ return ret;
+}
+
+SYSCALL_DEFINE0(munlockall)
+{
+ int ret;
+
+ down_write(&current->mm->mmap_sem);
+ ret = do_mlockall(0);
+ up_write(&current->mm->mmap_sem);
+ return ret;
+}
+
+/*
+ * Objects with different lifetime than processes (SHM_LOCK and SHM_HUGETLB
+ * shm segments) get accounted against the user_struct instead.
+ */
+static DEFINE_SPINLOCK(shmlock_user_lock);
+
+int user_shm_lock(size_t size, struct user_struct *user)
+{
+ unsigned long lock_limit, locked;
+ int allowed = 0;
+
+ locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ lock_limit = rlimit(RLIMIT_MEMLOCK);
+ if (lock_limit == RLIM_INFINITY)
+ allowed = 1;
+ lock_limit >>= PAGE_SHIFT;
+ spin_lock(&shmlock_user_lock);
+ if (!allowed &&
+ locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
+ goto out;
+ get_uid(user);
+ user->locked_shm += locked;
+ allowed = 1;
+out:
+ spin_unlock(&shmlock_user_lock);
+ return allowed;
+}
+
+void user_shm_unlock(size_t size, struct user_struct *user)
+{
+ spin_lock(&shmlock_user_lock);
+ user->locked_shm -= (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+ spin_unlock(&shmlock_user_lock);
+ free_uid(user);
+}