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Re: [Cluster-devel] [PATCH] mkfs.gfs2: Follow symlinks before checking device contents

On 06/28/2012 06:52 PM, Andrew Price wrote:
On 06/28/2012 11:01 AM, Steven Whitehouse wrote:

Yes, v2 is ok too. I think I missed that in my first pass over my email
today. To do this properly, we should be opening the path that we are
passed, and then doing the remaining operations with just the fd. We
could do that with "file" if we used the -f - option and passed the fd
as standard input to the process.

The only way I can think of passing the fd to file -f - would be the C
equivalent of:

   printf "/proc/$pid/fd/$fd" | file -f -

Which would mean adding another pipe() and fork(). So we might as well
just shorten it to:

   file "/proc/$pid/fd/$fd"

Would this solve the race condition problem? Or am I misunderstanding
how you intended it to be done?

I didn't get a reply to this. Does the above method seem sensible or would we need to read the start of the file/device ourselves and pipe it into 'file -' to avoid opening the file twice?


That way we also remove any possible race conditions too, but this is
good enough for now,


On Thu, 2012-06-28 at 10:58 +0100, Andrew Price wrote:
Hi Steve,

On 06/28/2012 10:16 AM, Steven Whitehouse wrote:

Looks good. ACK,

This one was obsoleted by the v2 patch I posted on the 21st. If you
prefer this one though I can push it instead.



On Wed, 2012-06-20 at 16:47 +0100, Andrew Price wrote:
When using symlinks with mkfs.gfs2 it reports what the symlink points
to instead of the contents of the device, like so:

   # ./mkfs.gfs2 -p lock_nolock /dev/vg/test
   This will destroy any data on /dev/vg/test.
   It appears to contain: symbolic link to `../dm-3'

This patch resolves symlinks before checking the device contents to
the output more informative:

   # ./mkfs.gfs2 -p lock_nolock /dev/vg/test
   This will destroy any data on /dev/vg/test.
   It appears to contain: GFS2 Filesystem (blocksize 4096,
lockproto lock_nolock)

Signed-off-by: Andrew Price <anprice redhat com>
   gfs2/mkfs/main_mkfs.c |    9 ++++++++-
   1 files changed, 8 insertions(+), 1 deletions(-)

diff --git a/gfs2/mkfs/main_mkfs.c b/gfs2/mkfs/main_mkfs.c
index e6b00a0..f8e4741 100644
--- a/gfs2/mkfs/main_mkfs.c
+++ b/gfs2/mkfs/main_mkfs.c
@@ -531,6 +531,7 @@ void main_mkfs(int argc, char *argv[])
       int error;
       int rgsize_specified = 0;
       unsigned char uuid[16];
+    char *absname;

       memset(sdp, 0, sizeof(struct gfs2_sbd));
       sdp->bsize = -1;
@@ -560,11 +561,17 @@ void main_mkfs(int argc, char *argv[])

+    absname = canonicalize_file_name(sdp->device_name);
+    if (absname == NULL) {
+        perror(_("Could not find the absolute path of the device"));
+        exit(EXIT_FAILURE);
+    }
       if (!sdp->override) {
           printf( _("This will destroy any data on %s.\n"),
-        check_dev_content(sdp->device_name);
+        check_dev_content(absname);
+    free(absname);

       if (sdp->bsize == -1) {
           if (S_ISREG(sdp->dinfo.stat.st_mode))

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