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flock: make flock(1) work on NFSv4 

To pleace an exclusive lock on a file, NFSv4 requires
the file to be opened RW because of the emulation of flock()
by fcntl():

http://www.spinics.net/lists/linux-nfs/msg18502.html

So instead of O_RDONLY, open the file in O_RDWR if access()
indicates it is possible (unless shared lock is requested).

From: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Petr Uzel <petr.uzel@suse.cz>
This commit is contained in:
Petr Uzel 2011-09-15 10:19:17 +02:00 committed by Karel Zak
parent 716e6f5c9a
commit 87d83b6ad2
1 changed files with 5 additions and 2 deletions
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7
sys-utils/flock.c
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@ -129,6 +129,7 @@ int main(int argc, char *argv[])
int have_timeout = 0;
int type = LOCK_EX;
int block = 0;
int open_accmode;
int fd = -1;
int opt, ix;
int do_close = 0;
@ -211,9 +212,11 @@ int main(int argc, char *argv[])
}
filename = argv[optind];
fd = open(filename, O_RDONLY|O_NOCTTY|O_CREAT, 0666);
open_accmode = ((type == LOCK_SH || access(filename, R_OK|W_OK) < 0) ?
O_RDONLY : O_RDWR);
fd = open(filename, open_accmode|O_NOCTTY|O_CREAT, 0666);
/* Linux doesn't like O_CREAT on a directory, even though it should be a
no-op */
no-op; POSIX doesn't allow O_RDWR or O_WRONLY */
if (fd < 0 && errno == EISDIR)
fd = open(filename, O_RDONLY|O_NOCTTY);