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Subject: Re: [PATCH] [nfs-utils] fix method to check if mounted already
To:     =?UTF-8?B?5bC55YmR6Jm5?= <yin-jianhong@163.com>
Cc:     "linux-nfs@vger.kernel.org" <linux-nfs@vger.kernel.org>
References: <20181025041518.24465-1-yin-jianhong@163.com>
 <81f5caf3-c802-4563-7924-53259e875369@RedHat.com>
 <252a171e.6801.166ae43c6af.Coremail.yin-jianhong@163.com>
From:   Steve Dickson <SteveD@RedHat.com>
Message-ID: <b5662fac-247a-2f42-c062-ac1c3eb7b526@RedHat.com>
Date:   Fri, 26 Oct 2018 08:07:36 -0400
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On 10/25/18 10:46 PM, 尹剑虹 wrote:
> Hi
> 
> commit 2e5533976c76c1 still test fail
> please see the reproducer.
It works for me... 

# mount -ocontext=system_u:object_r:xferlog_t:s0,sharecache localhost:/tmp /mnt/nfsmp
# mount -ocontext=system_u:object_r:user_home_dir_t:s0,sharecache localhost:/tmp /mnt/tmpfs
mount.nfs: /mnt/tmpfs is busy or already mounted

steved.
> 
> 
> 	
> 尹剑虹
> 邮箱：yin-jianhong@163.com
> 
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> 
> 签名由 网易邮箱大师 <https://mail.163.com/dashi/dlpro.html?from=mail88> 定制
> 
>         On 10/25/2018 23:38, Steve Dickson <mailto:SteveD@RedHat.com> wrote:
>         Hello,
> 
>         On 10/25/18 12:15 AM, Jianhong.Yin wrote:
>         > reproducer:
>         > '''
>         > mkdir /expdir /mnt/nfsmp /mnt/tmpfs
>         > echo "/expdir *(rw,no_root_squash)" >/etc/exports
>         > service nfs restart
>         > mount -t tmpfs tmpfs /mnt/tmpfs
>         > mount -osharecache localhost:/expdir /mnt/nfsmp #success
>         > mount -osharecache localhost:/expdir /mnt/nfsmp #mounted already, return 0(pass)
>         > mount -osharecache localhost:/expdir /mnt/tmpfs #success
>         > mount -osharecache localhost:/expdir /mnt/tmpfs #mounted already, return 0(pass)
>         > umount /mnt/nfsmp
>         > umount /mnt/tmpfs
>         >
>         > mount -ocontext=system_u:object_r:xferlog_t:s0,sharecache localhost:/expdir /mnt/nfsmp
>         > mount -ocontext=system_u:object_r:user_home_dir_t:s0,sharecache localhost:/expdir /mnt/tmpfs
>         > [[ $? = 0 ]] && echo "***test fail: hasn't mounted, should return fail ***"
>         > '''
>         >
>         > Signed-off-by: Jianhong Yin <yin-jianhong@163.com>
>         > ---
>         >  support/include/misc.h    |  1 +
>         >  support/misc/mountpoint.c | 26 +++++++++++++++++++++++++-
>         >  utils/mount/stropts.c     |  4 +---
>         >  3 files changed, 27 insertions(+), 4 deletions(-)
>         >
>         > diff --git a/support/include/misc.h b/support/include/misc.h
>         > index 06e2a0c..6a146e4 100644
>         > --- a/support/include/misc.h
>         > +++ b/support/include/misc.h
>         > @@ -19,6 +19,7 @@ char *generic_make_pathname(const char *, const char *);
>         >  _Bool generic_setup_basedir(const char *, const char *, char *, const size_t);
>         >  
>         >  extern int is_mountpoint(char *path);
>         > +extern int is_mounted_already(const char *fsname, const char *dir);
>         >  
>         >  /* size of the file pointer buffers for rpc procfs files */
>         >  #define RPC_CHAN_BUF_SIZE 32768
>         > diff --git a/support/misc/mountpoint.c b/support/misc/mountpoint.c
>         > index 9f9ce44..e21d529 100644
>         > --- a/support/misc/mountpoint.c
>         > +++ b/support/misc/mountpoint.c
>         > @@ -4,8 +4,10 @@
>         >   */
>         >  
>         >  #include <string.h>
>         > -#include "xcommon.h"
>         >  #include <sys/stat.h>
>         > +#include <stdio.h>
>         > +#include <mntent.h>
>         > +#include "xcommon.h"
>         >  #include "misc.h"
>         >  
>         >  int
>         > @@ -38,3 +40,25 @@ is_mountpoint(char *path)
>         >       free(dotdot);
>         >       return rv;
>         >  }
>         > +
>         > +int
>         > +is_mounted_already(const char *fsname, const char *dir)
>         > +{
>         > +     struct mntent *ent;
>         > +     FILE *fp;
>         > +     int ret = 0;
>         > +
>         > +     fp = setmntent("/proc/mounts", "r");
>         > +     if (fp == NULL) {
>         > +          perror("[unlikely] setmntent(3) fail");
>         > +          exit(1);
>         > +     }
>         > +     while (NULL != (ent = getmntent(fp))) {
>         > +          if (!strcmp(ent->mnt_fsname, fsname) && !strcmp(ent->mnt_dir, dir)) {
>         > +               ret = 1;
>         > +               break;
>         > +          }
>         > +     }
>         > +     endmntent(fp);
>         > +     return ret;
>         > +}
>         This does not scale on a large machines, especially when all that
>         is needed is two stat()s... one on the directory and one on the
>         parent directory.
> 
>         > diff --git a/utils/mount/stropts.c b/utils/mount/stropts.c
>         > index eed0356..0ee13bc 100644
>         > --- a/utils/mount/stropts.c
>         > +++ b/utils/mount/stropts.c
>         > @@ -1079,9 +1079,7 @@ static int nfsmount_fg(struct nfsmount_info *mi)
>         >            if (nfs_try_mount(mi))
>         >                 return EX_SUCCESS;
>         >  
>         > -#pragma GCC diagnostic ignored "-Wdiscarded-qualifiers"
>         > -          if (errno == EBUSY && is_mountpoint(mi->node))
>         > -#pragma GCC diagnostic warning "-Wdiscarded-qualifiers"
>         > +          if (errno == EBUSY && is_mounted_already(mi->spec, mi->node))
>         >                 /*
>         >                  * EBUSY can happen when mounting a filesystem that
>         >                  * is already mounted or when the context= are
>         >
>         This has been fixed with commit 2e5533976c76c1
> 
>         steved.
>