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* [PATCHv4 1/2] mm: rearrange madvise code to allow for reuse
@ 2013-10-30 21:54 Colin Cross
  2013-10-30 21:54 ` [PATCHv4 2/2] mm: add a field to store names for private anonymous memory Colin Cross
  0 siblings, 1 reply; 2+ messages in thread
From: Colin Cross @ 2013-10-30 21:54 UTC (permalink / raw)
  To: linux-kernel, Pekka Enberg, Dave Hansen, Peter Zijlstra,
	Ingo Molnar, Oleg Nesterov, Eric W. Biederman, Jan Glauber,
	John Stultz
  Cc: Colin Cross, Rob Landley, Cyrill Gorcunov, Kees Cook,
	Serge E. Hallyn, David Rientjes, Al Viro, Hugh Dickins,
	Rik van Riel, Mel Gorman, Michel Lespinasse, Tang Chen,
	Robin Holt, Shaohua Li, Sasha Levin, Johannes Weiner,
	Minchan Kim, Andrew Morton, Rasmus Villemoes,
	open list:MEMORY MANAGEMENT

Refactor the madvise syscall to allow for parts of it to be reused by a
prctl syscall that affects vmas.

Move the code that walks vmas in a virtual address range into a function
that takes a function pointer as a parameter.  The only caller for now is
sys_madvise, which uses it to call madvise_vma_behavior on each vma, but
the next patch will add an additional caller.

Move handling all vma behaviors inside madvise_behavior, and rename it to
madvise_vma_behavior.

Move the code that updates the flags on a vma, including splitting or
merging the vma as necessary, into a new function called
madvise_update_vma.  The next patch will add support for updating a new
anon_name field as well.

Signed-off-by: Colin Cross <ccross@android.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Jan Glauber <jan.glauber@gmail.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Rob Landley <rob@landley.net>
Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Cc: Kees Cook <keescook@chromium.org>
Cc: "Serge E. Hallyn" <serge.hallyn@ubuntu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Michel Lespinasse <walken@google.com>
Cc: Tang Chen <tangchen@cn.fujitsu.com>
Cc: Robin Holt <holt@sgi.com>
Cc: Shaohua Li <shli@fusionio.com>
Cc: Sasha Levin <sasha.levin@oracle.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---
 mm/madvise.c | 272 +++++++++++++++++++++++++++++++++--------------------------
 1 file changed, 151 insertions(+), 121 deletions(-)

diff --git a/mm/madvise.c b/mm/madvise.c
index 539eeb96b323..aa346f87edbb 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -39,65 +39,20 @@ static int madvise_need_mmap_write(int behavior)
 }
 
 /*
- * We can potentially split a vm area into separate
- * areas, each area with its own behavior.
+ * Update the vm_flags on regiion of a vma, splitting it or merging it as
+ * necessary.  Must be called with mmap_sem held for writing;
  */
-static long madvise_behavior(struct vm_area_struct *vma,
-		     struct vm_area_struct **prev,
-		     unsigned long start, unsigned long end, int behavior)
+static int madvise_update_vma(struct vm_area_struct *vma,
+		     struct vm_area_struct **prev, unsigned long start,
+		     unsigned long end, unsigned long new_flags)
 {
 	struct mm_struct *mm = vma->vm_mm;
-	int error = 0;
 	pgoff_t pgoff;
-	unsigned long new_flags = vma->vm_flags;
-
-	switch (behavior) {
-	case MADV_NORMAL:
-		new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
-		break;
-	case MADV_SEQUENTIAL:
-		new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
-		break;
-	case MADV_RANDOM:
-		new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
-		break;
-	case MADV_DONTFORK:
-		new_flags |= VM_DONTCOPY;
-		break;
-	case MADV_DOFORK:
-		if (vma->vm_flags & VM_IO) {
-			error = -EINVAL;
-			goto out;
-		}
-		new_flags &= ~VM_DONTCOPY;
-		break;
-	case MADV_DONTDUMP:
-		new_flags |= VM_DONTDUMP;
-		break;
-	case MADV_DODUMP:
-		if (new_flags & VM_SPECIAL) {
-			error = -EINVAL;
-			goto out;
-		}
-		new_flags &= ~VM_DONTDUMP;
-		break;
-	case MADV_MERGEABLE:
-	case MADV_UNMERGEABLE:
-		error = ksm_madvise(vma, start, end, behavior, &new_flags);
-		if (error)
-			goto out;
-		break;
-	case MADV_HUGEPAGE:
-	case MADV_NOHUGEPAGE:
-		error = hugepage_madvise(vma, &new_flags, behavior);
-		if (error)
-			goto out;
-		break;
-	}
+	int error;
 
 	if (new_flags == vma->vm_flags) {
 		*prev = vma;
-		goto out;
+		return 0;
 	}
 
 	pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
@@ -113,13 +68,13 @@ static long madvise_behavior(struct vm_area_struct *vma,
 	if (start != vma->vm_start) {
 		error = split_vma(mm, vma, start, 1);
 		if (error)
-			goto out;
+			return error;
 	}
 
 	if (end != vma->vm_end) {
 		error = split_vma(mm, vma, end, 0);
 		if (error)
-			goto out;
+			return error;
 	}
 
 success:
@@ -128,10 +83,7 @@ success:
 	 */
 	vma->vm_flags = new_flags;
 
-out:
-	if (error == -ENOMEM)
-		error = -EAGAIN;
-	return error;
+	return 0;
 }
 
 #ifdef CONFIG_SWAP
@@ -337,6 +289,77 @@ static long madvise_remove(struct vm_area_struct *vma,
 	return error;
 }
 
+/*
+ * Apply an madvise behavior to a region of a vma.  madvise_update_vma
+ * will handle splitting a vm area into separate areas, each area with its own
+ * behavior.
+ */
+static int madvise_vma_behavior(struct vm_area_struct *vma,
+		     struct vm_area_struct **prev,
+		     unsigned long start, unsigned long end,
+		     unsigned long behavior)
+{
+	int error = 0;
+	unsigned long new_flags = vma->vm_flags;
+
+	switch (behavior) {
+	case MADV_REMOVE:
+		return madvise_remove(vma, prev, start, end);
+	case MADV_WILLNEED:
+		return madvise_willneed(vma, prev, start, end);
+	case MADV_DONTNEED:
+		return madvise_dontneed(vma, prev, start, end);
+	case MADV_NORMAL:
+		new_flags = new_flags & ~VM_RAND_READ & ~VM_SEQ_READ;
+		break;
+	case MADV_SEQUENTIAL:
+		new_flags = (new_flags & ~VM_RAND_READ) | VM_SEQ_READ;
+		break;
+	case MADV_RANDOM:
+		new_flags = (new_flags & ~VM_SEQ_READ) | VM_RAND_READ;
+		break;
+	case MADV_DONTFORK:
+		new_flags |= VM_DONTCOPY;
+		break;
+	case MADV_DOFORK:
+		if (vma->vm_flags & VM_IO) {
+			error = -EINVAL;
+			goto out;
+		}
+		new_flags &= ~VM_DONTCOPY;
+		break;
+	case MADV_DONTDUMP:
+		new_flags |= VM_DONTDUMP;
+		break;
+	case MADV_DODUMP:
+		if (new_flags & VM_SPECIAL) {
+			error = -EINVAL;
+			goto out;
+		}
+		new_flags &= ~VM_DONTDUMP;
+		break;
+	case MADV_MERGEABLE:
+	case MADV_UNMERGEABLE:
+		error = ksm_madvise(vma, start, end, behavior, &new_flags);
+		if (error)
+			goto out;
+		break;
+	case MADV_HUGEPAGE:
+	case MADV_NOHUGEPAGE:
+		error = hugepage_madvise(vma, &new_flags, behavior);
+		if (error)
+			goto out;
+		break;
+	}
+
+	error = madvise_update_vma(vma, prev, start, end, new_flags);
+
+out:
+	if (error == -ENOMEM)
+		error = -EAGAIN;
+	return error;
+}
+
 #ifdef CONFIG_MEMORY_FAILURE
 /*
  * Error injection support for memory error handling.
@@ -375,22 +398,6 @@ static int madvise_hwpoison(int bhv, unsigned long start, unsigned long end)
 }
 #endif
 
-static long
-madvise_vma(struct vm_area_struct *vma, struct vm_area_struct **prev,
-		unsigned long start, unsigned long end, int behavior)
-{
-	switch (behavior) {
-	case MADV_REMOVE:
-		return madvise_remove(vma, prev, start, end);
-	case MADV_WILLNEED:
-		return madvise_willneed(vma, prev, start, end);
-	case MADV_DONTNEED:
-		return madvise_dontneed(vma, prev, start, end);
-	default:
-		return madvise_behavior(vma, prev, start, end, behavior);
-	}
-}
-
 static int
 madvise_behavior_valid(int behavior)
 {
@@ -421,6 +428,73 @@ madvise_behavior_valid(int behavior)
 }
 
 /*
+ * Walk the vmas in range [start,end), and call the visit function on each one.
+ * The visit function will get start and end parameters that cover the overlap
+ * between the current vma and the original range.  Any unmapped regions in the
+ * original range will result in this function returning -ENOMEM while still
+ * calling the visit function on all of the existing vmas in the range.
+ * Must be called with the mmap_sem held for reading or writing.
+ */
+static
+int madvise_walk_vmas(unsigned long start, unsigned long end,
+		unsigned long arg,
+		int (*visit)(struct vm_area_struct *vma,
+			struct vm_area_struct **prev, unsigned long start,
+			unsigned long end, unsigned long arg))
+{
+	struct vm_area_struct *vma;
+	struct vm_area_struct *prev;
+	unsigned long tmp;
+	int unmapped_error = 0;
+
+	/*
+	 * If the interval [start,end) covers some unmapped address
+	 * ranges, just ignore them, but return -ENOMEM at the end.
+	 * - different from the way of handling in mlock etc.
+	 */
+	vma = find_vma_prev(current->mm, start, &prev);
+	if (vma && start > vma->vm_start)
+		prev = vma;
+
+	for (;;) {
+		int error;
+
+		/* Still start < end. */
+		if (!vma)
+			return -ENOMEM;
+
+		/* Here start < (end|vma->vm_end). */
+		if (start < vma->vm_start) {
+			unmapped_error = -ENOMEM;
+			start = vma->vm_start;
+			if (start >= end)
+				break;
+		}
+
+		/* Here vma->vm_start <= start < (end|vma->vm_end) */
+		tmp = vma->vm_end;
+		if (end < tmp)
+			tmp = end;
+
+		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
+		error = visit(vma, &prev, start, tmp, arg);
+		if (error)
+			return error;
+		start = tmp;
+		if (prev && start < prev->vm_end)
+			start = prev->vm_end;
+		if (start >= end)
+			break;
+		if (prev)
+			vma = prev->vm_next;
+		else	/* madvise_remove dropped mmap_sem */
+			vma = find_vma(current->mm, start);
+	}
+
+	return unmapped_error;
+}
+
+/*
  * The madvise(2) system call.
  *
  * Applications can use madvise() to advise the kernel how it should
@@ -464,9 +538,7 @@ madvise_behavior_valid(int behavior)
  */
 SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 {
-	unsigned long end, tmp;
-	struct vm_area_struct *vma, *prev;
-	int unmapped_error = 0;
+	unsigned long end;
 	int error = -EINVAL;
 	int write;
 	size_t len;
@@ -501,52 +573,10 @@ SYSCALL_DEFINE3(madvise, unsigned long, start, size_t, len_in, int, behavior)
 	else
 		down_read(&current->mm->mmap_sem);
 
-	/*
-	 * If the interval [start,end) covers some unmapped address
-	 * ranges, just ignore them, but return -ENOMEM at the end.
-	 * - different from the way of handling in mlock etc.
-	 */
-	vma = find_vma_prev(current->mm, start, &prev);
-	if (vma && start > vma->vm_start)
-		prev = vma;
-
 	blk_start_plug(&plug);
-	for (;;) {
-		/* Still start < end. */
-		error = -ENOMEM;
-		if (!vma)
-			goto out;
-
-		/* Here start < (end|vma->vm_end). */
-		if (start < vma->vm_start) {
-			unmapped_error = -ENOMEM;
-			start = vma->vm_start;
-			if (start >= end)
-				goto out;
-		}
-
-		/* Here vma->vm_start <= start < (end|vma->vm_end) */
-		tmp = vma->vm_end;
-		if (end < tmp)
-			tmp = end;
-
-		/* Here vma->vm_start <= start < tmp <= (end|vma->vm_end). */
-		error = madvise_vma(vma, &prev, start, tmp, behavior);
-		if (error)
-			goto out;
-		start = tmp;
-		if (prev && start < prev->vm_end)
-			start = prev->vm_end;
-		error = unmapped_error;
-		if (start >= end)
-			goto out;
-		if (prev)
-			vma = prev->vm_next;
-		else	/* madvise_remove dropped mmap_sem */
-			vma = find_vma(current->mm, start);
-	}
-out:
+	error = madvise_walk_vmas(start, end, behavior, madvise_vma_behavior);
 	blk_finish_plug(&plug);
+
 	if (write)
 		up_write(&current->mm->mmap_sem);
 	else
-- 
1.8.4.1

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2013-10-30 21:54 [PATCHv4 1/2] mm: rearrange madvise code to allow for reuse Colin Cross
2013-10-30 21:54 ` [PATCHv4 2/2] mm: add a field to store names for private anonymous memory Colin Cross

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