On 10/19/2011 01:36 PM, J. Bruce Fields wrote: > On Wed, Oct 19, 2011 at 01:30:58PM -0400, Steve Dickson wrote: >> >> >> On 10/19/2011 01:22 PM, Jeff Layton wrote: >>> On Wed, 19 Oct 2011 13:10:19 -0400 >>> Steve Dickson <SteveD@xxxxxxxxxx> wrote: >>> >>>> >>>> >>>> On 10/19/2011 12:36 PM, Jeff Layton wrote: >>>>> On Wed, 19 Oct 2011 11:34:30 -0400 >>>>> Steve Dickson <steved@xxxxxxxxxx> wrote: >>>>> >>>>>> This patch is a following on to commit 7a802337. Using the >>>>>> tool in https://bugzilla.redhat.com/show_bug.cgi?id=695916 >>>>>> caused the fflush() and fclose() to fail in turn causing >>>>>> corruption in the mtab. >>>>>> >>>>>> The failures were in the internals of both calls. Switch those >>>>>> calls with the actual system calls eliminated the failures. >>>>>> >>>>>> Signed-off-by: Steve Dickson <steved@xxxxxxxxxx> >>>>>> --- >>>>>> support/nfs/nfs_mntent.c | 4 ++-- >>>>>> 1 files changed, 2 insertions(+), 2 deletions(-) >>>>>> >>>>>> diff --git a/support/nfs/nfs_mntent.c b/support/nfs/nfs_mntent.c >>>>>> index a2118a2..b80f270 100644 >>>>>> --- a/support/nfs/nfs_mntent.c >>>>>> +++ b/support/nfs/nfs_mntent.c >>>>>> @@ -117,7 +117,7 @@ void >>>>>> nfs_endmntent (mntFILE *mfp) { >>>>>> if (mfp) { >>>>>> if (mfp->mntent_fp) >>>>>> - fclose(mfp->mntent_fp); >>>>>> + close(fileno(mfp->mntent_fp)); >>>>>> if (mfp->mntent_file) >>>>>> free(mfp->mntent_file); >>>>>> free(mfp); >>>>>> @@ -147,7 +147,7 @@ nfs_addmntent (mntFILE *mfp, struct mntent *mnt) { >>>>>> free(m3); >>>>>> free(m4); >>>>>> if (res >= 0) { >>>>>> - res = fflush(mfp->mntent_fp); >>>>>> + res = fsync(fileno(mfp->mntent_fp)); >>>>> >>>>> fsync doesn't imply an fflush. With this, I think you may end up >>>>> without everything being committed to disk if part or all of it is >>>>> still in the file stream buffer. You probably want to do an fflush() >>>>> and then an fsync here. >>>> The problem was with the fflush() call. The call was causing the >>>> mount to drop core in turn causing mtab corruption. Changing that >>>> call to a fsync() worked just fine... no corruption... every time! >>>> >>> >>> Ahh, then you have another problem here too then. Most likely it was >>> crashing because it caught a SIGXFSZ. Writing out the mtab should not >>> be affected by signals. >> So calling fflush() generates a SIGXFSZ and call fsync() does not... > > fflush() must hit this because it's calling write() to write out the > stream buffer.... > > But lock_mtab() should have set SIGXFSZ to be ignored; is that not > happening? This is the case. The following patch cause SIGXFSZ to be ignored. diff -up ./utils/mount/fstab.c.orig ./utils/mount/fstab.c --- ./utils/mount/fstab.c.orig 2011-10-19 13:28:57.318132000 -0400 +++ ./utils/mount/fstab.c 2011-10-19 14:02:07.715039000 -0400 @@ -387,8 +387,9 @@ lock_mtab (void) { sa.sa_flags = 0; sigfillset (&sa.sa_mask); - while (sigismember (&sa.sa_mask, ++sig) != -1 - && sig != SIGCHLD) { + while (sigismember (&sa.sa_mask, ++sig) != -1) { + if (sig == SIGCHLD) + continue; if (sig == SIGALRM) sa.sa_handler = setlkw_timeout; else Now all this does is cause mount to ignore the fact that the write() during the fflush() fails, which causes the following warning during the umount. [mntent]: warning: no final newline at the end of /etc/mtab [mntent]: warning: no final newline at the end of /etc/mtab [mntent]: warning: no final newline at the end of /etc/mtab I can live with those warnings.... steved. > >> I really don't see what the problem is is call simply calling fsync() >> which clearly works? > > We want to make sure the problem's really fixed. > > --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
