If a page is truncated out from underneath us it is not nice to segfault. Other
fs's just returm VM_FAULT_NOPAGE which will make userspace retry the fault. If
you are doing O_DIRECT to the same file which you are mmap'ing you will get
segfaults because sometims O_DIRECT will invalidate the mapping pages which will
make it disappear in the middle of the fault, which on ext4 will result in a
segfault, but everybody else this works fine. Fixing this makes the
O_DIRECT/mmap test not crash. Thanks,
Signed-off-by: Josef Bacik <josef@xxxxxxxxxx>
---
fs/ext4/inode.c | 32 +++++++++++++-------------------
1 files changed, 13 insertions(+), 19 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1ad7d10..16d727c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5843,7 +5843,8 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
struct page *page = vmf->page;
loff_t size;
unsigned long len;
- int ret = -EINVAL;
+ int ret = VM_FAULT_NOPAGE;
+ int err;
void *fsdata;
struct file *file = vma->vm_file;
struct inode *inode = file->f_path.dentry->d_inode;
@@ -5862,13 +5863,11 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
/* page got truncated from under us? */
goto out_unlock;
}
- ret = 0;
+ ret = VM_FAULT_LOCKED;
wait_on_page_writeback(page);
- if (PageMappedToDisk(page)) {
- up_read(&inode->i_alloc_sem);
- return VM_FAULT_LOCKED;
- }
+ if (PageMappedToDisk(page))
+ goto out_unlock;
if (page->index == size >> PAGE_CACHE_SHIFT)
len = size & ~PAGE_CACHE_MASK;
@@ -5883,10 +5882,8 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
*/
if (page_has_buffers(page)) {
if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
- ext4_bh_unmapped)) {
- up_read(&inode->i_alloc_sem);
- return VM_FAULT_LOCKED;
- }
+ ext4_bh_unmapped))
+ goto out_unlock;
}
unlock_page(page);
/*
@@ -5896,28 +5893,25 @@ int ext4_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
* write_end call. lock_page prevent this from happening
* on the same page though
*/
- ret = mapping->a_ops->write_begin(file, mapping, page_offset(page),
+ ret = VM_FAULT_SIGBUS;
+ err = mapping->a_ops->write_begin(file, mapping, page_offset(page),
len, AOP_FLAG_UNINTERRUPTIBLE, &page, &fsdata);
- if (ret < 0)
+ if (err < 0)
goto out_unlock;
- ret = mapping->a_ops->write_end(file, mapping, page_offset(page),
+ err = mapping->a_ops->write_end(file, mapping, page_offset(page),
len, len, page, fsdata);
- if (ret < 0)
+ if (err < 0)
goto out_unlock;
- ret = 0;
/*
* write_begin/end might have created a dirty page and someone
* could wander in and start the IO. Make sure that hasn't
* happened.
*/
+ ret = VM_FAULT_LOCKED;
lock_page(page);
wait_on_page_writeback(page);
- up_read(&inode->i_alloc_sem);
- return VM_FAULT_LOCKED;
out_unlock:
- if (ret)
- ret = VM_FAULT_SIGBUS;
up_read(&inode->i_alloc_sem);
return ret;
}
--
1.7.5.2
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