From: David Woodhouse <dwmw2@infradead.org>
To: linux-kernel@vger.kernel.org
Subject: RFC: mmap(PROT_READ, MAP_SHARED) fails if !writepage.
Date: Fri, 08 Nov 2002 22:49:02 +0000 [thread overview]
Message-ID: <24305.1036795742@passion.cambridge.redhat.com> (raw)
Why does a _readonly_ mapping fail if the file system has no writepage
method?
do_mmap_pgoff() sets VM_MAYWRITE on the vma and then generic_file_mmap()
refuses to allow it.
Suggested patch below.... or should I just hack fsx-linux to use
MAP_PRIVATE for its readonly mappings and ignore it?
--- 1.157/mm/filemap.c Sun Nov 3 02:55:27 2002
+++ edited/mm/filemap.c Fri Nov 8 22:08:22 2002
@@ -1311,9 +1311,12 @@
struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
struct inode *inode = mapping->host;
- if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE)) {
- if (!mapping->a_ops->writepage)
+ if ((vma->vm_flags & VM_SHARED) && (vma->vm_flags & VM_MAYWRITE) &&
+ !mapping->a_ops->writepage) {
+ if (vma->vm_flags & VM_WRITE)
return -EINVAL;
+ else
+ vma->vm_flags &= ~VM_MAYWRITE;
}
if (!mapping->a_ops->readpage)
return -ENOEXEC;
--
dwmw2
next reply other threads:[~2002-11-08 22:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-11-08 22:49 David Woodhouse [this message]
2002-11-08 23:31 ` RFC: mmap(PROT_READ, MAP_SHARED) fails if !writepage Linus Torvalds
2002-11-08 23:50 ` David Woodhouse
2002-11-09 2:46 ` Linus Torvalds
2002-11-09 16:36 ` David Woodhouse
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