From ea13a86463fd0c26c2c209c53dc46b8eff81bad4 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 24 May 2011 00:23:35 +0200 Subject: vfs: Block mmapped writes while the fs is frozen We should not allow file modification via mmap while the filesystem is frozen. So block in block_page_mkwrite() while the filesystem is frozen. We cannot do the blocking wait in __block_page_mkwrite() since e.g. ext4 will want to call that function with transaction started in some cases and that would deadlock. But we can at least do the non-blocking reliable check in __block_page_mkwrite() which is the hardest part anyway. We have to check for frozen filesystem with the page marked dirty and under page lock with which we then return from ->page_mkwrite(). Only that way we cannot race with writeback done by freezing code - either we mark the page dirty after the writeback has started, see freezing in progress and block, or writeback will wait for our page lock which is released only when the fault is done and then writeback will writeout and writeprotect the page again. Reviewed-by: Christoph Hellwig Signed-off-by: Jan Kara Signed-off-by: Al Viro --- include/linux/buffer_head.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/buffer_head.h') diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h index 2bf6a9136a9..503c8a6b307 100644 --- a/include/linux/buffer_head.h +++ b/include/linux/buffer_head.h @@ -230,6 +230,8 @@ static inline int block_page_mkwrite_return(int err) return VM_FAULT_NOPAGE; if (err == -ENOMEM) return VM_FAULT_OOM; + if (err == -EAGAIN) + return VM_FAULT_RETRY; /* -ENOSPC, -EDQUOT, -EIO ... */ return VM_FAULT_SIGBUS; } -- cgit v1.2.3-70-g09d2