Messages in this thread | | | From | Hallvard Breien Furuseth <> | Subject | PROBLEM: Failed open() with O_DIRECT creates file | Date | Wed, 07 Sep 2016 17:10:49 +0200 |
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If the filesystem does not support O_DIRECT, then open(...O_CREAT|O_DIRECT..) fails but creates the file anyway.
Eric Sandeen@RedHat thought a fix would need a lot of vfs restructuring. (I reported this in 2013 to RedHat (bug#1008073), but just realized he was talking about "upstream" so maybe the report didn't get further.)
Linux 3.10.0-327.28.3.el7.x86_64, RHEL 7.2 (Maipo). The bug existed at least since 2.6.18-348.6.1.el5.
To reproduce, run this as:
./a.out /dev/test-direct.dat
(Originally I wrote to /dev/shm/, but tmpfs now accepts O_DIRECT.)
#define _GNU_SOURCE #include <errno.h> #include <fcntl.h> #include <stdio.h> #include <sys/stat.h> #include <unistd.h>
int main(int argc, char *argv[]) { char *fname = argc > 1 ? argv[1] : "test-direct.dat"; int fd = open(fname, O_WRONLY|O_CREAT|O_EXCL|O_DIRECT, 0666); int e = fd < 0 ? errno : 0;
if (fd >= 0) puts("open() succeeded"); else perror("open() error"); if ((access(fname, F_OK) == 0) != (fd >= 0 || e == EEXIST)) puts(fd < 0 ? "Created file anyway!" : "File disappeared!");
if (e != EEXIST) unlink(fname); return 0; }
-- Hallvard
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