Rohit Seth wrote on Friday, October 07, 2005 2:29 PM
> On Fri, 2005-10-07 at 10:47 -0700, Adam Litke wrote:
> > If I were to spend time coding up a patch to remove truncation
> > support for hugetlbfs, would it be something other people would
> > want to see merged as well?
>
> In its current form, there is very little use of huegtlb truncate
> functionality. Currently it only allows reducing the size of hugetlb
> backing file.
>
> IMO it will be useful to keep and enhance this capability so that
> apps can dynamically reduce or increase the size of backing files
> (for example based on availability of memory at any time).
Yup, here is a patch to enhance that capability. It is more of bring
ftruncate on hugetlbfs file a step closer to the same semantics for
file on other file systems.
---
Add expanding ftruncate to hugetlbfs.
Signed-off-by: Ken Chen <[email protected]>
--- linux-2.6.14-rc3/fs/hugetlbfs/inode.c.orig 2005-10-07 18:07:38.131373873 -0700
+++ linux-2.6.14-rc3/fs/hugetlbfs/inode.c 2005-10-08 00:31:15.951404405 -0700
@@ -327,20 +327,20 @@ hugetlb_vmtruncate_list(struct prio_tree
}
}
-/*
- * Expanding truncates are not allowed.
- */
static int hugetlb_vmtruncate(struct inode *inode, loff_t offset)
{
unsigned long pgoff;
struct address_space *mapping = inode->i_mapping;
-
- if (offset > inode->i_size)
- return -EINVAL;
+ struct vm_area_struct *vma;
+ struct prio_tree_iter iter;
+ int ret = 0;
BUG_ON(offset & ~HPAGE_MASK);
pgoff = offset >> HPAGE_SHIFT;
+ if (offset > inode->i_size)
+ goto do_expand;
+
inode->i_size = offset;
spin_lock(&mapping->i_mmap_lock);
if (!prio_tree_empty(&mapping->i_mmap))
@@ -348,6 +348,18 @@ static int hugetlb_vmtruncate(struct ino
spin_unlock(&mapping->i_mmap_lock);
truncate_hugepages(mapping, offset);
return 0;
+
+do_expand:
+ spin_lock(&mapping->i_mmap_lock);
+ vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, pgoff, ULONG_MAX) {
+ ret = hugetlb_prefault(mapping, vma);
+ if (ret == 0)
+ inode->i_size = offset;
+ else
+ break;
+ }
+ spin_unlock(&mapping->i_mmap_lock);
+ return ret;
}
static int hugetlbfs_setattr(struct dentry *dentry, struct iattr *attr)
--- linux-2.6.14-rc3/mm/hugetlb.c.orig 2005-10-07 23:16:42.789349826 -0700
+++ linux-2.6.14-rc3/mm/hugetlb.c 2005-10-07 23:25:04.175085872 -0700
@@ -340,7 +340,7 @@ void zap_hugepage_range(struct vm_area_s
int hugetlb_prefault(struct address_space *mapping, struct vm_area_struct *vma)
{
- struct mm_struct *mm = current->mm;
+ struct mm_struct *mm = vma->vm_mm;
unsigned long addr;
int ret = 0;
@@ -360,6 +360,8 @@ int hugetlb_prefault(struct address_spac
ret = -ENOMEM;
goto out;
}
+ if (pte_present(*pte))
+ continue;
idx = ((addr - vma->vm_start) >> HPAGE_SHIFT)
+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
-
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