diff options
Diffstat (limited to 'fs/buffer.c')
| -rw-r--r-- | fs/buffer.c | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/fs/buffer.c b/fs/buffer.c index f6ad8f9b8fa5..b0675bfe8207 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); |