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| author | Zhang, Yanmin <yanmin.zhang@intel.com> | 2006-07-10 04:44:49 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-07-10 13:24:21 -0700 |
| commit | b6174df5eec9cdfd598c03d6d0807e344e109213 (patch) | |
| tree | d61c8627138a8feee31de8320e337251d567fca9 /fs | |
| parent | d6b7d3b62069be60d5b13358bac8670dacdd7a81 (diff) | |
| download | lwn-b6174df5eec9cdfd598c03d6d0807e344e109213.tar.gz lwn-b6174df5eec9cdfd598c03d6d0807e344e109213.zip | |
[PATCH] mmap zero-length hugetlb file with PROT_NONE to protect a hugetlb virtual area
Sometimes, applications need below call to be successful although
"/mnt/hugepages/file1" doesn't exist.
fd = open("/mnt/hugepages/file1", O_CREAT|O_RDWR, 0755);
*addr = mmap(NULL, 0x1024*1024*256, PROT_NONE, 0, fd, 0);
As for regular pages (or files), above call does work, but as for huge
pages, above call would fail because hugetlbfs_file_mmap would fail if
(!(vma->vm_flags & VM_WRITE) && len > inode->i_size).
This capability on huge page is useful on ia64 when the process wants to
protect one area on region 4, so other threads couldn't read/write this
area. A famous JVM (Java Virtual Machine) implementation on IA64 needs the
capability.
Signed-off-by: Zhang Yanmin <yanmin.zhang@intel.com>
Cc: David Gibson <david@gibson.dropbear.id.au>
Cc: Hugh Dickins <hugh@veritas.com>
[ Expand-on-mmap semantics again... this time matching normal fs's. wli ]
Acked-by: William Lee Irwin III <wli@holomorphy.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/hugetlbfs/inode.c | 4 |
1 files changed, 1 insertions, 3 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c index 6449cb697967..c3920c96dadf 100644 --- a/fs/hugetlbfs/inode.c +++ b/fs/hugetlbfs/inode.c @@ -83,8 +83,6 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) ret = -ENOMEM; len = vma_len + ((loff_t)vma->vm_pgoff << PAGE_SHIFT); - if (!(vma->vm_flags & VM_WRITE) && len > inode->i_size) - goto out; if (vma->vm_flags & VM_MAYSHARE && hugetlb_reserve_pages(inode, vma->vm_pgoff >> (HPAGE_SHIFT-PAGE_SHIFT), @@ -93,7 +91,7 @@ static int hugetlbfs_file_mmap(struct file *file, struct vm_area_struct *vma) ret = 0; hugetlb_prefault_arch_hook(vma->vm_mm); - if (inode->i_size < len) + if (vma->vm_flags & VM_WRITE && inode->i_size < len) inode->i_size = len; out: mutex_unlock(&inode->i_mutex); |