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authorHugh Dickins <hugh@veritas.com>2005-09-03 15:54:53 -0700
committerLinus Torvalds <torvalds@evo.osdl.org>2005-09-05 00:05:44 -0700
commit836d5ffd34550901ea024347693e689273ded8aa (patch)
treeb4dbbbe436eae38aa2f0f5d333608f64c6338cd8 /mm
parent53e9a6159fdc6419874ce4d86d3577dbedc77b62 (diff)
downloadlinux-linaro-836d5ffd34550901ea024347693e689273ded8aa.tar.gz
[PATCH] mm: fix madvise vma merging
Better late than never, I've at last reviewed the madvise vma merging going into 2.6.13. Remove a pointless check and fix two little bugs - a simple test (with /proc/<pid>/maps hacked to show ReadHints) showed both mismerges in practice: though being madvise, neither was disastrous. 1. Correct placement of the success label in madvise_behavior: as in mprotect_fixup and mlock_fixup, it is necessary to update vm_flags when vma_merge succeeds (to handle the exceptional Case 8 noted in the comments above vma_merge itself). 2. Correct initial value of prev when starting part way into a vma: as in sys_mprotect and do_mlock, it needs to be set to vma in this case (vma_merge handles only that minimum of cases shown in its comments). 3. If find_vma_prev sets prev, then the vma it returns is prev->vm_next, so it's pointless to make that same assignment again in sys_madvise. 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 'mm')
-rw-r--r--mm/madvise.c9
1 files changed, 5 insertions, 4 deletions
diff --git a/mm/madvise.c b/mm/madvise.c
index c8c01a12fea..4454936f87d 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -37,7 +37,7 @@ static long madvise_behavior(struct vm_area_struct * vma,
if (new_flags == vma->vm_flags) {
*prev = vma;
- goto success;
+ goto out;
}
pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
@@ -62,6 +62,7 @@ static long madvise_behavior(struct vm_area_struct * vma,
goto out;
}
+success:
/*
* vm_flags is protected by the mmap_sem held in write mode.
*/
@@ -70,7 +71,6 @@ static long madvise_behavior(struct vm_area_struct * vma,
out:
if (error == -ENOMEM)
error = -EAGAIN;
-success:
return error;
}
@@ -237,8 +237,9 @@ asmlinkage long sys_madvise(unsigned long start, size_t len_in, int behavior)
* - different from the way of handling in mlock etc.
*/
vma = find_vma_prev(current->mm, start, &prev);
- if (!vma && prev)
- vma = prev->vm_next;
+ if (vma && start > vma->vm_start)
+ prev = vma;
+
for (;;) {
/* Still start < end. */
error = -ENOMEM;