You may not have done anything from client that does:

fd = open(“foo”, O_RDWR + O_CREAT + O_TRUNC, 0666)

Try

echo foo > /mnt/foo

from the client, and then run it again (so you get both the create case and the already exists case.

Frank

From: Sachin Punadikar [mailto:punadikar.sachin@gmail.com]
Sent: Wednesday, October 24, 2018 4:07 AM
To: Daniel Gryniewicz <dang@redhat.com>
Cc: devel@lists.nfs-ganesha.org
Subject: [NFS-Ganesha-Devel] Re: read-only open causing file to be truncated with NFSv4/ganesha.

Hi Daniel,

Here is the code snippet from fsal_open2 function:

        /* Handle attribute size = 0 here, normalize to FSAL_O_TRUNC

         * instead of setting ATTR_SIZE.

         */

        if (attr != NULL &&

            FSAL_TEST_MASK(attr->valid_mask, ATTR_SIZE) &&

            attr->filesize == 0) {

                LogFullDebug(COMPONENT_FSAL, "Truncate");

                /* Handle truncate to zero on open */

                openflags |= FSAL_O_TRUNC;

                /* Don't set the size if we later set the attributes */

                FSAL_UNSET_MASK(attr->valid_mask, ATTR_SIZE);

        }

If I enable full debug, I could see "Truncate" being logged only when the file is new. For existing files, "Truncate" log entry was never seen.

Hence I mentioned that it gets applied to only new files.

On Tue, Oct 23, 2018 at 7:27 PM Daniel Gryniewicz <dang@redhat.com> wrote:

Where are you seeing this?  It looks to me like FSAL_O_TRUNC is applied
on all opens.

Daniel

On 10/23/2018 06:42 AM, Sachin Punadikar wrote:
> I have uploaded a patch to fix this
> (https://review.gerrithub.io/c/ffilz/nfs-ganesha/+/430435)
> But I have a question on this.
> As per the code, the O_TRUNC gets applied (via open_flags) only when it
> is file create. If the file pre-exists, O_TRUNC is not applied to
> open_flags.
> Was wondering, why we need O_TRUNC while creating new file, anyway it
> will be of size 0 ?
> As per my little understanding the O_TRUNC should be applicable if we
> are opening a pre-existing file. Correct me if I am wrong.
>
> On Mon, Oct 15, 2018 at 6:32 PM Daniel Gryniewicz <dang@redhat.com
> <mailto:dang@redhat.com>> wrote:
>
>     This seems like a bug.  My guess is that either status2() shouldn't
>     return O_TRUNC, or it shouldn't be saved in the fd to begin with.
>     O_TRUNC is a transitory flag, only useful at the time of the open
>     itself.
>
>     Fixing the common status2() is simplest; otherwise we need to fix all
>     the FSALs.
>
>     Daniel
>
>     On 10/12/2018 08:12 PM, Pradeep wrote:
>      > Hello,
>      >
>      > I'm seeing an issue with a specific application flow and with
>     ganesha
>      > server (2.6.5). Here is what the application does:
>      >
>      > - fd1 = open (file1, O_WRONLY|O_CREAT|O_TRUNC)
>      >    Ganesha creates a state and stores the flags in fd->openflags
>     (see
>      > vfs_open2())
>      > - write (fd1, ....)
>      > - fd2 = open(file1, O_RDONLY)
>      >    Ganesha finds the state for the first open, finds the flags
>     and calls
>      > fsal_reopen2() with old and new flags OR'd together. This causes the
>      > file to be truncated because the original open was done with O_TRUNC.
>      >
>      > I don't see this behavior with kernel NFS or a local filesystem. Any
>      > suggestions on fixing this? Here is a quick and dirty program to
>      > reproduce it - you can see that the second stat prints zero as
>     size with
>      > a mount from Ganesha server.
>      >
>      > #include <stdio.h>
>      > #include <stdlib.h>
>      > #include <sys/types.h>
>      > #include <sys/stat.h>
>      > #include <fcntl.h>
>      > #include <sys/stat.h>
>      > #include <unistd.h>
>      >
>      > int main(int argc, char **argv)
>      > {
>      >    char *fn = argv[1];
>      >    int fd;
>      >    char buf[1024];
>      >    struct stat stbuf;
>      >    int rc;
>      >
>      >
>      >    fd = open(fn, O_WRONLY|O_CREAT|O_TRUNC, 0666);
>      >    printf("open(%s) = %d\n", fn, fd);
>      >
>      >    ssize_t ret;
>      >    ret = write(fd, buf, sizeof(buf));
>      >    printf("write returned %ld\n", ret);
>      >
>      >    rc = stat(fn, &stbuf);
>      >    printf("size: %ld\n", stbuf.st_size);
>      >
>      >    int fd1;
>      >    fd1 = open(fn, O_RDONLY);
>      >    printf("open(%s) = %d\n", fn, fd1);
>      >
>      >    rc = stat(fn, &stbuf);
>      >    printf("size: %ld\n", stbuf.st_size);
>      > }
>      >
>      > Thanks,
>      > Pradeep
>      >
>      >
>      >
>      > _______________________________________________
>      > Devel mailing list -- devel@lists.nfs-ganesha.org
>     <mailto:devel@lists.nfs-ganesha.org>
>      > To unsubscribe send an email to devel-leave@lists.nfs-ganesha.org
>     <mailto:devel-leave@lists.nfs-ganesha.org>
>      >
>     _______________________________________________
>     Devel mailing list -- devel@lists.nfs-ganesha.org
>     <mailto:devel@lists.nfs-ganesha.org>
>     To unsubscribe send an email to devel-leave@lists.nfs-ganesha.org
>     <mailto:devel-leave@lists.nfs-ganesha.org>
>
>
>
> --
> with regards,
> Sachin Punadikar

--

with regards,

Sachin Punadikar