On Fri, 2010-10-01 at 14:12 -0400, Trond Myklebust wrote:
> However, it looks to me as if the right thing to do when the
> page->mapping has changed would be to do the same thing as
> block_page_mkwrite(), and just return VM_FAULT_NOPAGE so that the VM can
> retry the fault.
> IMO: We should only SIGBUS if the calls to nfs_flush_incompatible()
> and/or nfs_updatepage() fail.
>
> Cheers
> Trond
IOW: Something like the following patch.
Cheers
Trond
---------------------------------------------------------------------------
NFS: Don't SIGBUS if nfs_vm_page_mkwrite races with a cache invalidation
From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
In the case where we lock the page, and then find out that the page has
been thrown out of the page cache, we should just return VM_FAULT_NOPAGE.
This is what block_page_mkwrite() does in these situations.
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/file.c | 17 ++++++++---------
1 files changed, 8 insertions(+), 9 deletions(-)
diff --git a/fs/nfs/file.c b/fs/nfs/file.c
index 05bf3c0..6d95e24 100644
--- a/fs/nfs/file.c
+++ b/fs/nfs/file.c
@@ -551,7 +551,7 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
struct file *filp = vma->vm_file;
struct dentry *dentry = filp->f_path.dentry;
unsigned pagelen;
- int ret = -EINVAL;
+ int ret = VM_FAULT_NOPAGE;
struct address_space *mapping;
dfprintk(PAGECACHE, "NFS: vm_page_mkwrite(%s/%s(%ld), offset %lld)\n",
@@ -567,21 +567,20 @@ static int nfs_vm_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
if (mapping != dentry->d_inode->i_mapping)
goto out_unlock;
- ret = 0;
pagelen = nfs_page_length(page);
if (pagelen == 0)
goto out_unlock;
- ret = nfs_flush_incompatible(filp, page);
- if (ret != 0)
- goto out_unlock;
+ ret = VM_FAULT_LOCKED;
+ if (nfs_flush_incompatible(filp, page) == 0 &&
+ nfs_updatepage(filp, page, 0, pagelen) == 0)
+ goto out;
- ret = nfs_updatepage(filp, page, 0, pagelen);
+ ret = VM_FAULT_SIGBUS;
out_unlock:
- if (!ret)
- return VM_FAULT_LOCKED;
unlock_page(page);
- return VM_FAULT_SIGBUS;
+out:
+ return ret;
}
static const struct vm_operations_struct nfs_file_vm_ops = {
--
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