[Date Prev][Date Next]
Re: (ITS#7682) LMDB: [PATCH] mdb_env_copy should retry open() if O_DIRECT fails
- To: openldap-its@OpenLDAP.org
- Subject: Re: (ITS#7682) LMDB: [PATCH] mdb_env_copy should retry open() if O_DIRECT fails
- From: firstname.lastname@example.org
- Date: Fri, 13 Sep 2013 21:09:51 GMT
- Auto-submitted: auto-generated (OpenLDAP-ITS)
On 09/05/2013 06:33 PM, Howard Chu wrote:
> email@example.com wrote:
>> Full_Name: Salvador Ortiz
>> Version: 24
>> OS: Linux
>> Submission from: (NULL) (188.8.131.52)
>> If the OS defines O_DIRECT mdb_env_copy unconditionally uses it, but
>> to open(2): "Some file systems may not implement the flag and
>> open() will
>> fail with EINVAL if it is used."
>> In this cases mdb_env_copy should retry without the flag.
>> The attached patch implements that.
> Thanks, applied.
Thank you Howard, but I found an unexpected problem with the patch as
If the call fails because O_DIRECT, in a "tmpfs" in my Fedora 19 '/tmp',
the file is left created anyway! so the retry fails because O_EXCL|O_CREAT.
I consider this undocumented behavior for "open", buggy or at least ugly.
(A simple test program in ftp://ftp.msg.com.mx/pub/varios/o_direct.c)
I propose the following:
--- a/liblmdb/mdb.c 2013-09-05 17:31:01.498090281 -0500
+++ b/liblmdb/mdb.c 2013-09-13 14:45:00.918717292 -0500
@@ -4250,9 +4250,16 @@
/* The OS supports O_DIRECT, try with it */
newfd = open(lpath, O_WRONLY|O_CREAT|O_EXCL|O_DIRECT, 0666);
/* But open can fail if O_DIRECT isn't supported by the file system
- * so retry without the flag
+ * so retry without the flag.
+ * Sept 13 2013.
+ * On a tmpfs, at least, an open with O_DIRECT fails,
+ * BUT the file is created anyway!!
+ * Fortunately seems that other errors are reported before EINVAL
+ * So, we need to remove it before retry open.
if (newfd == INVALID_HANDLE_VALUE && ErrCode() == EINVAL)
+ (void)unlink(lpath) ,
newfd = open(lpath, O_WRONLY|O_CREAT|O_EXCL, 0666);
What do you think?