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Re: [PATCH v9 5/6] xfs: Add proper versioning support to fs_quota_stat

To: Chandra Seetharaman <sekharan@xxxxxxxxxx>
Subject: Re: [PATCH v9 5/6] xfs: Add proper versioning support to fs_quota_stat
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 25 Jun 2013 16:43:12 +1000
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1372042107-27332-6-git-send-email-sekharan@xxxxxxxxxx>
References: <1372042107-27332-1-git-send-email-sekharan@xxxxxxxxxx> <1372042107-27332-6-git-send-email-sekharan@xxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Sun, Jun 23, 2013 at 09:48:26PM -0500, Chandra Seetharaman wrote:
> Added appropriate pads and code for backward compatibility.
> 
> Copied over the old version as it is different from the newer padded
> version.
> 
> New callers of the system call have to set the version of the data
> structure being passed, and kernel will fill as much data as requested.

Is there are test for this? i.e. that the different version
structures return the same information?

> 
> Signed-off-by: Chandra Seetharaman <sekharan@xxxxxxxxxx>
> ---
>  fs/gfs2/quota.c                |    3 --
>  fs/quota/quota.c               |   49 +++++++++++++++++++++++++++++++++-
>  fs/xfs/xfs_qm_syscalls.c       |    4 ---
>  fs/xfs/xfs_super.c             |    5 +--
>  include/uapi/linux/dqblk_xfs.h |   57 
> +++++++++++++++++++++++++++++++++++-----
>  5 files changed, 99 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/gfs2/quota.c b/fs/gfs2/quota.c
> index c7c840e..ca0dccd 100644
> --- a/fs/gfs2/quota.c
> +++ b/fs/gfs2/quota.c
> @@ -1443,9 +1443,6 @@ static int gfs2_quota_get_xstate(struct super_block *sb,
>  {
>       struct gfs2_sbd *sdp = sb->s_fs_info;
>  
> -     memset(fqs, 0, sizeof(struct fs_quota_stat));
> -     fqs->qs_version = FS_QSTAT_VERSION;
> -
>       switch (sdp->sd_args.ar_quota) {
>       case GFS2_QUOTA_ON:
>               fqs->qs_flags |= (FS_QUOTA_UDQ_ENFD | FS_QUOTA_GDQ_ENFD);
> diff --git a/fs/quota/quota.c b/fs/quota/quota.c
> index c7314f1..ae6526e 100644
> --- a/fs/quota/quota.c
> +++ b/fs/quota/quota.c
> @@ -207,12 +207,57 @@ static int quota_setxstate(struct super_block *sb, int 
> cmd, void __user *addr)
>  static int quota_getxstate(struct super_block *sb, void __user *addr)
>  {
>       struct fs_quota_stat fqs;
> -     int ret;
> +     struct fs_quota_stat_v1 fqs_v1;
> +     int ret, size;
> +     void *fqsp;
>  
>       if (!sb->s_qcop->get_xstate)
>               return -ENOSYS;
> +
> +     memset(&fqs, 0, sizeof(struct fs_quota_stat));
> +     if (copy_from_user(&fqs, addr, 1)) /* just get the version */
> +             return -EFAULT;
> +
> +     switch (fqs.qs_version) {
> +     case FS_QSTAT_VERSION_2:
> +             size = FS_QSTAT_V2_SIZE;
> +             break;
> +     default:
> +             fqs.qs_version = FS_QSTAT_VERSION;
> +             /* fallthrough */
> +     case FS_QSTAT_VERSION:
> +             size = FS_QSTAT_V1_SIZE;
> +             break;
> +     }
> +
>       ret = sb->s_qcop->get_xstate(sb, &fqs);
> -     if (!ret && copy_to_user(addr, &fqs, sizeof(fqs)))
> +     if (ret)
> +             return ret;
> +
> +     if (fqs.qs_version == FS_QSTAT_VERSION) {
> +             fqs_v1.qs_version = fqs.qs_version;
> +             fqs_v1.qs_flags = fqs.qs_flags;
> +             fqs_v1.qs_pad = 0;
> +
> +             fqs_v1.qs_uquota.qfs_ino = fqs.qs_uquota.qfs_ino;
> +             fqs_v1.qs_uquota.qfs_nblks = fqs.qs_uquota.qfs_nblks;
> +             fqs_v1.qs_uquota.qfs_nextents = fqs.qs_uquota.qfs_nextents;
> +
> +             fqs_v1.qs_gquota.qfs_ino = fqs.qs_gquota.qfs_ino;
> +             fqs_v1.qs_gquota.qfs_nblks = fqs.qs_gquota.qfs_nblks;
> +             fqs_v1.qs_gquota.qfs_nextents = fqs.qs_gquota.qfs_nextents;
> +
> +             fqs_v1.qs_incoredqs = fqs.qs_incoredqs;
> +             fqs_v1.qs_btimelimit = fqs.qs_btimelimit;
> +             fqs_v1.qs_itimelimit = fqs.qs_itimelimit;
> +             fqs_v1.qs_rtbtimelimit = fqs.qs_rtbtimelimit;
> +             fqs_v1.qs_bwarnlimit = fqs.qs_bwarnlimit;
> +             fqs_v1.qs_iwarnlimit = fqs.qs_iwarnlimit;
> +             fqsp = &fqs_v1;
> +     } else
> +             fqsp = &fqs;
> +
> +     if (copy_to_user(addr, fqsp, size))
>               return -EFAULT;
>       return ret;
>  }
> diff --git a/fs/xfs/xfs_qm_syscalls.c b/fs/xfs/xfs_qm_syscalls.c
> index d664a2d..1918f48 100644
> --- a/fs/xfs/xfs_qm_syscalls.c
> +++ b/fs/xfs/xfs_qm_syscalls.c
> @@ -420,9 +420,6 @@ xfs_qm_scall_getqstat(
>       bool                    tempgqip = false;
>       bool                    temppqip = false;
>  
> -     memset(out, 0, sizeof(fs_quota_stat_t));
> -
> -     out->qs_version = FS_QSTAT_VERSION;
>       if (!xfs_sb_version_hasquota(&mp->m_sb)) {
>               out->qs_uquota.qfs_ino = NULLFSINO;
>               out->qs_gquota.qfs_ino = NULLFSINO;
> @@ -432,7 +429,6 @@ xfs_qm_scall_getqstat(
>       out->qs_flags = (__uint16_t) xfs_qm_export_flags(mp->m_qflags &
>                                                       (XFS_ALL_QUOTA_ACCT|
>                                                        XFS_ALL_QUOTA_ENFD));
> -     out->qs_pad = 0;
>       out->qs_uquota.qfs_ino = mp->m_sb.sb_uquotino;
>       out->qs_gquota.qfs_ino = mp->m_sb.sb_gquotino;
>       if (&out->qs_gquota != &out->qs_pquota)
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 1bcc017..ab90539 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -554,14 +554,13 @@ xfs_showargs(
>       else if (mp->m_qflags & XFS_UQUOTA_ACCT)
>               seq_puts(m, "," MNTOPT_UQUOTANOENF);
>  
> -     /* Either project or group quotas can be active, not both */
> -
>       if (mp->m_qflags & XFS_PQUOTA_ACCT) {
>               if (mp->m_qflags & XFS_PQUOTA_ENFD)
>                       seq_puts(m, "," MNTOPT_PRJQUOTA);
>               else
>                       seq_puts(m, "," MNTOPT_PQUOTANOENF);
> -     } else if (mp->m_qflags & XFS_GQUOTA_ACCT) {
> +     }
> +     if (mp->m_qflags & XFS_GQUOTA_ACCT) {
>               if (mp->m_qflags & XFS_GQUOTA_ENFD)
>                       seq_puts(m, "," MNTOPT_GRPQUOTA);
>               else
> diff --git a/include/uapi/linux/dqblk_xfs.h b/include/uapi/linux/dqblk_xfs.h
> index f17e3bb..e8ca23b 100644
> --- a/include/uapi/linux/dqblk_xfs.h
> +++ b/include/uapi/linux/dqblk_xfs.h
> @@ -47,6 +47,7 @@
>   * 512 bytes.
>   */
>  #define FS_DQUOT_VERSION     1       /* fs_disk_quota.d_version */
> +
>  typedef struct fs_disk_quota {
>       __s8            d_version;      /* version of this structure */
>       __s8            d_flags;        /* FS_{USER,PROJ,GROUP}_QUOTA */
> @@ -137,31 +138,73 @@ typedef struct fs_disk_quota {
>   * Provides a centralized way to get meta information about the quota 
> subsystem.
>   * eg. space taken up for user and group quotas, number of dquots currently
>   * incore.
> + * User space caller should set qs_version to the appropriate version
> + * of the fs_quota_stat data structure they are providing. Not providing
> + * a version will be treated as FS_QSTAT_VERSION.
>   */
>  #define FS_QSTAT_VERSION     1       /* fs_quota_stat.qs_version */
> +#define FS_QSTAT_VERSION_2   2       /* new field qs_pquota; realignment */
>  
>  /*
>   * Some basic information about 'quota files'.
>   */
> -typedef struct fs_qfilestat {
> +struct fs_qfilestat_v1 {
>       __u64           qfs_ino;        /* inode number */
>       __u64           qfs_nblks;      /* number of BBs 512-byte-blks */
>       __u32           qfs_nextents;   /* number of extents */
> -} fs_qfilestat_t;
> +};
>  
> -typedef struct fs_quota_stat {
> +struct fs_quota_stat_v1 {
>       __s8            qs_version;     /* version number for future changes */
>       __u16           qs_flags;       /* FS_QUOTA_{U,P,G}DQ_{ACCT,ENFD} */
>       __s8            qs_pad;         /* unused */
> -     fs_qfilestat_t  qs_uquota;      /* user quota storage information */
> -     fs_qfilestat_t  qs_gquota;      /* group quota storage information */
> -#define qs_pquota    qs_gquota
> +     struct fs_qfilestat_v1  qs_uquota;      /* user quota information */
> +     struct fs_qfilestat_v1  qs_gquota;      /* group quota information */
>       __u32           qs_incoredqs;   /* number of dquots incore */
>       __s32           qs_btimelimit;  /* limit for blks timer */      
>       __s32           qs_itimelimit;  /* limit for inodes timer */    
>       __s32           qs_rtbtimelimit;/* limit for rt blks timer */   
>       __u16           qs_bwarnlimit;  /* limit for num warnings */
>       __u16           qs_iwarnlimit;  /* limit for num warnings */
> -} fs_quota_stat_t;
> +};
> +
> +/*
> + * Some basic information about 'quota files'. Version 2.
> + */
> +struct fs_qfilestat {
> +     __u64           qfs_ino;        /* inode number */
> +     __u64           qfs_nblks;      /* number of BBs 512-byte-blks */
> +     __u32           qfs_nextents;   /* number of extents */
> +     __u8            qfs_pad[4];     /* pad for 8-byte alignment */

Just pad it as:

        __u32           qfs_pad;

So the size of the hole being filled is obvious.

> +};
> +
> +struct fs_quota_stat {
> +     __s8                    qs_version;     /* version for future changes */
> +     __u8                    qs_pad1;        /* pad for 16bit alignment */
> +     __u16                   qs_flags;       /* FS_QUOTA_.* flags */
> +     __u8                    qs_pad2[4];     /* pad for 8-byte alignment */

Actually, we can reorder this structure so there aren't intermediate
holes like this. The only thing that matters is that the first byte
is the version number. So:

struct fs_quota_stat {
        __s8                    qs_version;     /* version for future changes */
        __u8                    qs_pad1;        /* pad for 16bit alignment */
        __u16                   qs_flags;       /* FS_QUOTA_.* flags */
        __u32                   qs_incoredqs;   /* number of dquots incore */
        struct fs_qfilestat     qs_uquota;      /* user quota information */
        struct fs_qfilestat     qs_gquota;      /* group quota information */
        struct fs_qfilestat     qs_pquota;      /* project quota information */
        __s32                   qs_btimelimit;  /* limit for blks timer */
        __s32                   qs_itimelimit;  /* limit for inodes timer */
        __s32                   qs_rtbtimelimit;/* limit for rt blks timer */
        __u16                   qs_bwarnlimit;  /* limit for num warnings */
        __u16                   qs_iwarnlimit;  /* limit for num warnings */
        __u32                   qs_pad2;        /* pad for 8-byte alignment */
        __u64                   qs_pad3[8];     /* for future proofing */
};

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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