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-rw-r--r--fs/buffer.c24
1 files changed, 23 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index f6ad8f9..b0675bf 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2331,6 +2331,9 @@ EXPORT_SYMBOL(block_commit_write);
* page lock we can determine safely if the page is beyond EOF. If it is not
* beyond EOF, then the page is guaranteed safe against truncation until we
* unlock the page.
+ *
+ * Direct callers of this function should call vfs_check_frozen() so that page
+ * fault does not busyloop until the fs is thawed.
*/
int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
get_block_t get_block)
@@ -2362,6 +2365,18 @@ int __block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
if (unlikely(ret < 0))
goto out_unlock;
+ /*
+ * Freezing in progress? We check after the page is marked dirty and
+ * with page lock held so if the test here fails, we are sure freezing
+ * code will wait during syncing until the page fault is done - at that
+ * point page will be dirty and unlocked so freezing code will write it
+ * and writeprotect it again.
+ */
+ set_page_dirty(page);
+ if (inode->i_sb->s_frozen != SB_UNFROZEN) {
+ ret = -EAGAIN;
+ goto out_unlock;
+ }
return 0;
out_unlock:
unlock_page(page);
@@ -2372,8 +2387,15 @@ EXPORT_SYMBOL(__block_page_mkwrite);
int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
get_block_t get_block)
{
- int ret = __block_page_mkwrite(vma, vmf, get_block);
+ int ret;
+ struct super_block *sb = vma->vm_file->f_path.dentry->d_inode->i_sb;
+ /*
+ * This check is racy but catches the common case. The check in
+ * __block_page_mkwrite() is reliable.
+ */
+ vfs_check_frozen(sb, SB_FREEZE_WRITE);
+ ret = __block_page_mkwrite(vma, vmf, get_block);
return block_page_mkwrite_return(ret);
}
EXPORT_SYMBOL(block_page_mkwrite);
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