From: Marco Stornelli <marco.stornelli@xxxxxxxxx>
There aren't sufficient sync points for a fs for xip operations. In
particular for the mmap case. It can be not sufficient to lock/unlock
to do some operation inside get_xip_mem callback. For xip_file_read
it's really easy to write a fs specific wrapper, xip_file_write hold
i_mutex so no problem. With this patch we can avoid concurrent truncate
operation and xip mmap.
Signed-off-by: Marco Stornelli <marco.stornelli@xxxxxxxxx>
---
--- filemap_xip.c.orig 2011-09-10 17:16:56.000000000 +0200
+++ filemap_xip.c 2011-09-10 17:19:25.000000000 +0200
@@ -230,6 +230,7 @@ static int xip_file_fault(struct vm_area
int error;
/* XXX: are VM_FAULT_ codes OK? */
+ mutex_lock(&inode->i_mutex);
again:
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
if (vmf->pgoff >= size)
@@ -239,8 +240,10 @@ again:
&xip_mem, &xip_pfn);
if (likely(!error))
goto found;
- if (error != -ENODATA)
+ if (error != -ENODATA) {
+ mutex_unlock(&inode->i_mutex);
return VM_FAULT_OOM;
+ }
/* sparse block */
if ((vma->vm_flags & (VM_WRITE | VM_MAYWRITE)) &&
@@ -253,17 +256,22 @@ again:
error = mapping->a_ops->get_xip_mem(mapping, vmf->pgoff, 1,
&xip_mem, &xip_pfn);
mutex_unlock(&xip_sparse_mutex);
- if (error)
+ if (error) {
+ mutex_unlock(&inode->i_mutex);
return VM_FAULT_SIGBUS;
+ }
/* unmap sparse mappings at pgoff from all other vmas */
__xip_unmap(mapping, vmf->pgoff);
found:
err = vm_insert_mixed(vma, (unsigned long)vmf->virtual_address,
xip_pfn);
- if (err == -ENOMEM)
+ if (err == -ENOMEM) {
+ mutex_unlock(&inode->i_mutex);
return VM_FAULT_OOM;
+ }
BUG_ON(err);
+ mutex_unlock(&inode->i_mutex);
return VM_FAULT_NOPAGE;
} else {
int err, ret = VM_FAULT_OOM;
@@ -292,6 +300,7 @@ found:
out:
write_seqcount_end(&xip_sparse_seq);
mutex_unlock(&xip_sparse_mutex);
+ mutex_unlock(&inode->i_mutex);
return ret;
}
--
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