A simple rule of system calls is that you cannot return -ERESTARTSYS
after you've made non-idempotent changes. ocfs2 has run into this with
open(O_CREAT|O_EXCL). Once you've created the file, you can't restart
the open(), because O_CREAT|O_EXCL will trigger -EEXIST.
The problem is that ocfs2 is catching the signal ->permission(), called
by may_open(). This happens after ->create() has successfully created
the file. ocfs2_permission() has to get a cluster lock, and this is
what can be interrupted by a signal. Now, obviously we want to block
signals in the O_CREAT|O_EXCL case, but ocfs2_permission() has no way of
knowing it just got called from open_namei_create().
So we add the MAY_CREATE flag to permission(). open_namei_create() will
pass it to may_open(), and then ocfs2 can block signals in
ocfs2_permission() as appropriate. The same is true of any other
filesystem that has to do work in may_open().
Signed-off-by: Joel Becker <joel.becker@xxxxxxxxxx>
---
fs/namei.c | 2 +-
include/linux/fs.h | 1 +
2 files changed, 2 insertions(+), 1 deletions(-)
diff --git a/fs/namei.c b/fs/namei.c
index d11f404..d54cb98 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1623,7 +1623,7 @@ out_unlock:
if (error)
return error;
/* Don't check for write permission, don't truncate */
- return may_open(&nd->path, 0, flag & ~O_TRUNC);
+ return may_open(&nd->path, MAY_CREATE, flag & ~O_TRUNC);
}
/*
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 2620a8c..b1a454c 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -53,6 +53,7 @@ struct inodes_stat_t {
#define MAY_APPEND 8
#define MAY_ACCESS 16
#define MAY_OPEN 32
+#define MAY_CREATE 64
/*
* flags in file.f_mode. Note that FMODE_READ and FMODE_WRITE must correspond
--
1.6.3.3
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