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-rw-r--r--fs/ramfs/file-nommu.c31
-rw-r--r--include/linux/mm.h1
-rw-r--r--mm/nommu.c62
3 files changed, 64 insertions, 30 deletions
diff --git a/fs/ramfs/file-nommu.c b/fs/ramfs/file-nommu.c
index 266531343aae..1739a4aba25f 100644
--- a/fs/ramfs/file-nommu.c
+++ b/fs/ramfs/file-nommu.c
@@ -123,35 +123,6 @@ add_error:
/*****************************************************************************/
/*
- * check that file shrinkage doesn't leave any VMAs dangling in midair
- */
-static int ramfs_nommu_check_mappings(struct inode *inode,
- size_t newsize, size_t size)
-{
- struct vm_area_struct *vma;
- struct prio_tree_iter iter;
-
- down_write(&nommu_region_sem);
-
- /* search for VMAs that fall within the dead zone */
- vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
- newsize >> PAGE_SHIFT,
- (size + PAGE_SIZE - 1) >> PAGE_SHIFT
- ) {
- /* found one - only interested if it's shared out of the page
- * cache */
- if (vma->vm_flags & VM_SHARED) {
- up_write(&nommu_region_sem);
- return -ETXTBSY; /* not quite true, but near enough */
- }
- }
-
- up_write(&nommu_region_sem);
- return 0;
-}
-
-/*****************************************************************************/
-/*
*
*/
static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
@@ -169,7 +140,7 @@ static int ramfs_nommu_resize(struct inode *inode, loff_t newsize, loff_t size)
/* check that a decrease in size doesn't cut off any shared mappings */
if (newsize < size) {
- ret = ramfs_nommu_check_mappings(inode, newsize, size);
+ ret = nommu_shrink_inode_mappings(inode, size, newsize);
if (ret < 0)
return ret;
}
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 2265f28eb47a..60c467bfbabd 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1089,6 +1089,7 @@ extern void zone_pcp_update(struct zone *zone);
/* nommu.c */
extern atomic_long_t mmap_pages_allocated;
+extern int nommu_shrink_inode_mappings(struct inode *, size_t, size_t);
/* prio_tree.c */
void vma_prio_tree_add(struct vm_area_struct *, struct vm_area_struct *old);
diff --git a/mm/nommu.c b/mm/nommu.c
index 32be0cf51ba6..48a2ecfaf059 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -1914,3 +1914,65 @@ int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, in
mmput(mm);
return len;
}
+
+/**
+ * nommu_shrink_inode_mappings - Shrink the shared mappings on an inode
+ * @inode: The inode to check
+ * @size: The current filesize of the inode
+ * @newsize: The proposed filesize of the inode
+ *
+ * Check the shared mappings on an inode on behalf of a shrinking truncate to
+ * make sure that that any outstanding VMAs aren't broken and then shrink the
+ * vm_regions that extend that beyond so that do_mmap_pgoff() doesn't
+ * automatically grant mappings that are too large.
+ */
+int nommu_shrink_inode_mappings(struct inode *inode, size_t size,
+ size_t newsize)
+{
+ struct vm_area_struct *vma;
+ struct prio_tree_iter iter;
+ struct vm_region *region;
+ pgoff_t low, high;
+ size_t r_size, r_top;
+
+ low = newsize >> PAGE_SHIFT;
+ high = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
+
+ down_write(&nommu_region_sem);
+
+ /* search for VMAs that fall within the dead zone */
+ vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
+ low, high) {
+ /* found one - only interested if it's shared out of the page
+ * cache */
+ if (vma->vm_flags & VM_SHARED) {
+ up_write(&nommu_region_sem);
+ return -ETXTBSY; /* not quite true, but near enough */
+ }
+ }
+
+ /* reduce any regions that overlap the dead zone - if in existence,
+ * these will be pointed to by VMAs that don't overlap the dead zone
+ *
+ * we don't check for any regions that start beyond the EOF as there
+ * shouldn't be any
+ */
+ vma_prio_tree_foreach(vma, &iter, &inode->i_mapping->i_mmap,
+ 0, ULONG_MAX) {
+ if (!(vma->vm_flags & VM_SHARED))
+ continue;
+
+ region = vma->vm_region;
+ r_size = region->vm_top - region->vm_start;
+ r_top = (region->vm_pgoff << PAGE_SHIFT) + r_size;
+
+ if (r_top > newsize) {
+ region->vm_top -= r_top - newsize;
+ if (region->vm_end > region->vm_top)
+ region->vm_end = region->vm_top;
+ }
+ }
+
+ up_write(&nommu_region_sem);
+ return 0;
+}