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ocfs2: Fix ocfs2_page_mkwrite()

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This patch address two shortcomings in ocfs2_page_mkwrite():
1. Makes the function return better VM_FAULT_* errors.
2. It handles a error that is triggered when a page is dropped from the mapping
due to memory pressure. This patch locks the page to prevent that.

[Patch was cleaned up by Sunil Mushran.]

Signed-off-by: Wengang Wang <wen.gang.wang@oracle.com>
Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
This commit is contained in:
Wengang Wang
2011-07-24 10:36:54 -07:00
committed by Sunil Mushran
parent a035bff6b8
commit 5cffff9e29
2 changed files with 67 additions and 37 deletions
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53
fs/ocfs2/mmap.c
View File

@@ -61,7 +61,7 @@ static int ocfs2_fault(struct vm_area_struct *area, struct vm_fault *vmf)
static int __ocfs2_page_mkwrite(struct file *file, struct buffer_head *di_bh,
struct page *page)
{
int ret;
int ret = VM_FAULT_NOPAGE;
struct inode *inode = file->f_path.dentry->d_inode;
struct address_space *mapping = inode->i_mapping;
loff_t pos = page_offset(page);
@@ -71,32 +71,25 @@ static int __ocfs2_page_mkwrite(struct file *file, struct buffer_head *di_bh,
void *fsdata;
loff_t size = i_size_read(inode);
/*
* Another node might have truncated while we were waiting on
* cluster locks.
* We don't check size == 0 before the shift. This is borrowed
* from do_generic_file_read.
*/
last_index = (size - 1) >> PAGE_CACHE_SHIFT;
if (unlikely(!size || page->index > last_index)) {
ret = -EINVAL;
goto out;
}
/*
* The i_size check above doesn't catch the case where nodes
* truncated and then re-extended the file. We'll re-check the
* page mapping after taking the page lock inside of
* ocfs2_write_begin_nolock().
* There are cases that lead to the page no longer bebongs to the
* mapping.
* 1) pagecache truncates locally due to memory pressure.
* 2) pagecache truncates when another is taking EX lock against
* inode lock. see ocfs2_data_convert_worker.
*
* The i_size check doesn't catch the case where nodes truncated and
* then re-extended the file. We'll re-check the page mapping after
* taking the page lock inside of ocfs2_write_begin_nolock().
*
* Let VM retry with these cases.
*/
if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
/*
* the page has been umapped in ocfs2_data_downconvert_worker.
* So return 0 here and let VFS retry.
*/
ret = 0;
if ((page->mapping != inode->i_mapping) ||
(!PageUptodate(page)) ||
(page_offset(page) >= size))
goto out;
}
/*
* Call ocfs2_write_begin() and ocfs2_write_end() to take
@@ -116,17 +109,21 @@ static int __ocfs2_page_mkwrite(struct file *file, struct buffer_head *di_bh,
if (ret) {
if (ret != -ENOSPC)
mlog_errno(ret);
if (ret == -ENOMEM)
ret = VM_FAULT_OOM;
else
ret = VM_FAULT_SIGBUS;
goto out;
}
ret = ocfs2_write_end_nolock(mapping, pos, len, len, locked_page,
fsdata);
if (ret < 0) {
mlog_errno(ret);
if (!locked_page) {
ret = VM_FAULT_NOPAGE;
goto out;
}
ret = ocfs2_write_end_nolock(mapping, pos, len, len, locked_page,
fsdata);
BUG_ON(ret != len);
ret = 0;
ret = VM_FAULT_LOCKED;
out:
return ret;
}
@@ -168,8 +165,6 @@ static int ocfs2_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
out:
ocfs2_unblock_signals(&oldset);
if (ret)
ret = VM_FAULT_SIGBUS;
return ret;
}