Normal locking order is:
i_mutex
mmap_sem
However NFS's ->mmap hook, which is called under mmap_sem, can take i_mutex.
Avoid this potential deadlock by doing the work that requires i_mutex from
the new ->mmap_prepare().
[ Is this sufficient, or does it introduce a race? ]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
fs/nfs/file.c | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
Index: linux-2.6/fs/nfs/file.c
===================================================================
--- linux-2.6.orig/fs/nfs/file.c
+++ linux-2.6/fs/nfs/file.c
@@ -41,6 +41,9 @@
static int nfs_file_open(struct inode *, struct file *);
static int nfs_file_release(struct inode *, struct file *);
static loff_t nfs_file_llseek(struct file *file, loff_t offset, int origin);
+static int
+nfs_file_mmap_prepare(struct file * file, unsigned long len,
+ unsigned long prot, unsigned long flags, unsigned long pgoff);
static int nfs_file_mmap(struct file *, struct vm_area_struct *);
static ssize_t nfs_file_splice_read(struct file *filp, loff_t *ppos,
struct pipe_inode_info *pipe,
@@ -64,6 +67,7 @@ const struct file_operations nfs_file_op
.write = do_sync_write,
.aio_read = nfs_file_read,
.aio_write = nfs_file_write,
+ .mmap_prepare = nfs_file_mmap_prepare,
.mmap = nfs_file_mmap,
.open = nfs_file_open,
.flush = nfs_file_flush,
@@ -270,7 +274,8 @@ nfs_file_splice_read(struct file *filp,
}
static int
-nfs_file_mmap(struct file * file, struct vm_area_struct * vma)
+nfs_file_mmap_prepare(struct file * file, unsigned long len,
+ unsigned long prot, unsigned long flags, unsigned long pgoff)
{
struct dentry *dentry = file->f_path.dentry;
struct inode *inode = dentry->d_inode;
@@ -279,13 +284,17 @@ nfs_file_mmap(struct file * file, struct
dfprintk(VFS, "nfs: mmap(%s/%s)\n",
dentry->d_parent->d_name.name, dentry->d_name.name);
- status = nfs_revalidate_mapping(inode, file->f_mapping);
- if (!status) {
- vma->vm_ops = &nfs_file_vm_ops;
- vma->vm_flags |= VM_CAN_NONLINEAR;
- file_accessed(file);
- }
- return status;
+ return nfs_revalidate_mapping(inode, file->f_mapping);
+}
+
+static int
+nfs_file_mmap(struct file *file, struct vm_area_struct *vma)
+{
+ vma->vm_ops = &nfs_file_vm_ops;
+ vma->vm_flags |= VM_CAN_NONLINEAR;
+ file_accessed(file);
+
+ return 0;
}
/*
--
-
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