From 7187750e8dfa7a93135a145e10c88569d4e7d767 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 24 Mar 2011 14:21:58 +1100 Subject: [PATCH] open_dev_excl: allow device to be read-only. For many operations we don't need a writable device. So if opening O_RDWR fails in open_dev_excl, then try again O_RDONLY. If we really needed write, a subsequent operation will failed. But if we didn't, we succeed when otherwise we wouldn't have. Signed-off-by: NeilBrown --- util.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/util.c b/util.c index ef4406a1..e0671eb6 100644 --- a/util.c +++ b/util.c @@ -1015,12 +1015,17 @@ int open_dev_excl(int devnum) { char buf[20]; int i; + int flags = O_RDWR; sprintf(buf, "%d:%d", dev2major(devnum), dev2minor(devnum)); for (i=0 ; i<25 ; i++) { - int fd = dev_open(buf, O_RDWR|O_EXCL); + int fd = dev_open(buf, flags|O_EXCL); if (fd >= 0) return fd; + if (errno == EACCES && flags == O_RDWR) { + flags = O_RDONLY; + continue; + } if (errno != EBUSY) return fd; usleep(200000); -- 2.39.2