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Re: [PATCH] [RFC] Implement XFS_IOC_FSBULKSTAT_RANGE ioctl

To: Carlos Maiolino <cmaiolino@xxxxxxxxxx>, xfs@xxxxxxxxxxx
Subject: Re: [PATCH] [RFC] Implement XFS_IOC_FSBULKSTAT_RANGE ioctl
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Tue, 03 Mar 2015 14:58:04 -0600
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <1425393678-4550-1-git-send-email-cmaiolino@xxxxxxxxxx>
References: <1425393678-4550-1-git-send-email-cmaiolino@xxxxxxxxxx>
On 3/3/15 8:41 AM, Carlos Maiolino wrote:
> This patch aims to implement a ranged bulkstat ioctl, which will make users 
> able
> to bulkstat inodes in a filesystem based on range instead on rely only in a
> whole filesystem bulkstat.
> 
> This first implementation add a per AG bulkstat possibility, but it also adds
> the necessary infrastructure to implement different kinds of ranged bulkstat,
> like per block.
> 
> The patch is already working and I've been testing it for a while, so, I think
> it's time to send this patch out and ask for comments on it.
> 
> The core of the implementation is very similar with what xfs_bulsktat() does 
> by
> now, which, instead bulkstat the whole filesystem, it start/stop on the
> specified range.
> 
> As per Dave's suggesting, I added to  rgbulkreq structure (used to pass data
> to/from userland), a padding, so we can use the same structure for another 
> kind
> of ranged bulkstats without the need to actually change the structure size.
> 
> Signed-off-by: Carlos Maiolino <cmaiolino@xxxxxxxxxx>
> ---
>  fs/xfs/libxfs/xfs_fs.h |  12 +++
>  fs/xfs/xfs_ioctl.c     |  56 +++++++++++++
>  fs/xfs/xfs_itable.c    | 210 
> +++++++++++++++++++++++++++++++++++++++++++++++++
>  fs/xfs/xfs_itable.h    |  16 ++++
>  4 files changed, 294 insertions(+)
> 
> diff --git a/fs/xfs/libxfs/xfs_fs.h b/fs/xfs/libxfs/xfs_fs.h
> index 18dc721..88665aa 100644
> --- a/fs/xfs/libxfs/xfs_fs.h
> +++ b/fs/xfs/libxfs/xfs_fs.h
> @@ -334,6 +334,17 @@ typedef struct xfs_fsop_bulkreq {
>       __s32           __user *ocount; /* output count pointer         */
>  } xfs_fsop_bulkreq_t;
>  
> +typedef struct xfs_fsop_rgbulkreq {
> +     __u64           __user *lastip; /* last inode # pointer         */
> +     __s32           icount;         /* count of entries in buffer   */
> +     void            __user *ubuffer;/* user buffer for inode desc.  */
> +     __s32           __user *ocount; /* output count pointer         */
> +     __u64           start;          /* start point of rgbulkstat    */
> +     __u64           end;            /* end point of rgbulkstat      */

Ok, so this is a generic start/end, but your patch interprets them as AGs,
right?

> +     __u32           flags;          /* multipurpose flag field      */

unused...  Was the intent to be able to specify inode numbers or blocks as
a range as well, and maybe the flag tells XFS what the start/end numbers
mean?

If you intend start/end to have multiple possible meanings, I wouldn't
merge this patch without at least a requirement that the flags specify i.e.
BULKREQ_RANGE_AGNO or something, so that it's clear to the user and to the
code how the range is specified and interpreted.

It'd be trivial, in the ioctl entry code, to read the flag, interpret
start/end as blocks/inodes/ags, and convert the given values to inode numbers
(the smallest granularity we'd have).

> +     __u32           pad[5];         /* reserved space               */
> +} xfs_fsop_rgbulkreq_t;
> +
>  
>  /*
>   * Structures returned from xfs_inumbers routine (XFS_IOC_FSINUMBERS).
> @@ -556,6 +567,7 @@ typedef struct xfs_swapext
>  #define XFS_IOC_ATTRMULTI_BY_HANDLE  _IOW ('X', 123, struct 
> xfs_fsop_attrmulti_handlereq)
>  #define XFS_IOC_FSGEOMETRY        _IOR ('X', 124, struct xfs_fsop_geom)
>  #define XFS_IOC_GOINGDOWN         _IOR ('X', 125, __uint32_t)
> +#define XFS_IOC_FSBULKSTAT_RANGE     _IOWR('X', 126, struct 
> xfs_fsop_rgbulkreq)
>  /*   XFS_IOC_GETFSUUID ---------- deprecated 140      */
>  
>  
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index f7afb86..34a4de5 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -790,6 +790,59 @@ xfs_ioc_bulkstat(
>  }
>  
>  STATIC int
> +xfs_ioc_bulkstat_range(
> +     xfs_mount_t             *mp,
> +     unsigned int            cmd,
> +     void                    __user *arg)
> +{
> +
> +     xfs_fsop_rgbulkreq_t    rgbulkreq;
> +     int                     count;  /* # of records returned */
> +     xfs_ino_t               inlast; /* last inode number */
> +     int                     done;
> +     int                     error;
> +
> +     if (!capable(CAP_SYS_ADMIN))
> +             return -EPERM;
> +
> +     if (XFS_FORCED_SHUTDOWN(mp))
> +             return -EIO;
> +
> +     /* We do not support another ranged calls yet */
> +     if (cmd != XFS_IOC_FSBULKSTAT_RANGE)
> +             return -EINVAL;

I don't think this is necessary; the only way we can get here is if
cmd == XFS_IOC_FSBULKSTAT_RANGE.  What other cases do you envision?

> +
> +     if (copy_from_user(&rgbulkreq, arg, sizeof(xfs_fsop_rgbulkreq_t)))
> +             return -EFAULT;
> +
> +     if (copy_from_user(&inlast, rgbulkreq.lastip, sizeof(__s64)))
> +             return -EFAULT;
> +
> +     if ((count = rgbulkreq.icount) <= 0)
> +             return -EINVAL;
> +
> +     if (rgbulkreq.ubuffer == NULL)
> +             return -EINVAL;
> +
> +     error = xfs_bulkstat_range(mp, &inlast, &count, xfs_bulkstat_one,
> +                                sizeof(xfs_bstat_t), rgbulkreq.ubuffer,
> +                                rgbulkreq.start, rgbulkreq.end, &done);
> +
> +     if (error)
> +             return error;
> +
> +     if (rgbulkreq.ocount != NULL) {
> +             if (copy_to_user(rgbulkreq.lastip, &inlast, sizeof(xfs_ino_t)))
> +                     return -EFAULT;
> +
> +             if (copy_to_user(rgbulkreq.ocount, &count, sizeof(count)))
> +                     return -EFAULT;
> +     }
> +
> +     return 0;
> +}
> +
> +STATIC int
>  xfs_ioc_fsgeometry_v1(
>       xfs_mount_t             *mp,
>       void                    __user *arg)
> @@ -1555,6 +1608,9 @@ xfs_file_ioctl(
>       case XFS_IOC_FSINUMBERS:
>               return xfs_ioc_bulkstat(mp, cmd, arg);
>  
> +     case XFS_IOC_FSBULKSTAT_RANGE:
> +             return xfs_ioc_bulkstat_range(mp, cmd, arg);

There's only one possible cmd that gets passed to xfs_ioc_bulkstat_range
here, so there is no need to pass it in.

> +
>       case XFS_IOC_FSGEOMETRY_V1:
>               return xfs_ioc_fsgeometry_v1(mp, arg);
>  
> diff --git a/fs/xfs/xfs_itable.c b/fs/xfs/xfs_itable.c
> index 82e3142..d6b27ee 100644
> --- a/fs/xfs/xfs_itable.c
> +++ b/fs/xfs/xfs_itable.c
> @@ -530,6 +530,216 @@ del_cursor:
>       return error;
>  }
>  
> +/*
> + * Return stat information in bulk (by-inode) for specified
> + * filesystem range.
> + */
> +int
> +xfs_bulkstat_range(

*way* too much cut & paste from xfs_bulkstat() here.  Didn't Dave suggest a
refactoring which re-uses most of this code?

I had envisioned slightly extending xfs_bulkstat() to take an end inode
numbers by default it would do the entire fs.  (lastinop already specifies
the starting inde number).  With your ioctl entry point, lastinop could
be provided based on the start value, and end would be specified as well,
and all the same code would be re-used.

I think Dave had some other vision, but in any case, cut & paste of ~200 LOC
w/o any real changes won't fly.

Comments below, anyway.  ;)

> +     xfs_mount_t             *mp,    /* mount point for filesystem */
> +     xfs_ino_t               *lastinop, /* last inode returned */
> +     int                     *ubcountp, /* size of buffer/count returned */
> +     bulkstat_one_pf         formatter, /* func that'd fill a single buf */
> +     size_t                  statstruct_size, /* sizeof struct filling */
> +     char                    __user *ubuffer, /* buffer with inode stats */
> +     __u64                   start,  /* start bulkstat here */
> +     __u64                   end,    /* end bulkstat here */
> +     int                     *done) /* 1 if there are more stats to get */
> +{
> +     xfs_buf_t               *agbp;  /* agi header buffer */
> +     xfs_agino_t             agino;  /* inode # in allocation group */
> +     xfs_agnumber_t          agno;   /* allocation group number */
> +     xfs_btree_cur_t         *cur;   /* btree cursor for ialloc btree */
> +     size_t                  irbsize; /* size of irec buffer in bytes */
> +     xfs_inobt_rec_incore_t  *irbuf; /* start of irec buffer */
> +     int                     nirbuf; /* size of irbuf */
> +     int                     ubcount; /* size of user's buffer */
> +     struct xfs_bulkstat_agichunk ac;
> +     int                     error = 0;
> +
> +     /*
> +      * Get the last inode value, see if there is nothing to do.
> +      */

this comment isn't relevant in your copied code, at least not
to the code following it.

> +     if (*lastinop != 0)
> +             agno = XFS_INO_TO_AGNO(mp, *lastinop);
> +     else
> +             agno = start;
> +
> +     agino = XFS_INO_TO_AGINO(mp, *lastinop);
> +
> +     /*
> +      * If specified end is bigger than mp->m_sb.sb_agount, should we
> +      * gracefully interpret as if there is nothing to do, or trigger
> +      * an error?
> +      */

I think EINVAL would be reasonable here.

> +     if (agno >= mp->m_sb.sb_agcount) {
> +             *done = 1;
> +             *ubcountp = 0;
> +             return 0;
> +     }
> +
> +     ubcount = *ubcountp;
> +     ac.ac_ubuffer = &ubuffer;
> +     ac.ac_ubleft = ubcount * statstruct_size; /* bytes */
> +     ac.ac_ubelem = 0;
> +
> +     *ubcountp = 0;
> +     *done = 0;
> +
> +     irbuf = kmem_zalloc_greedy(&irbsize, PAGE_SIZE, PAGE_SIZE * 4);
> +     if (!irbuf)
> +             return -ENOMEM;
> +
> +     nirbuf = irbsize / sizeof(*irbuf);
> +
> +     /*
> +      * Loop over the allocation groups, starting from the last inode
> +      * returned; - means start of the allocation group.

"- means start" ?

> +      */
> +     while (agno <= end) {
> +             struct xfs_inobt_rec_incore     *irbp = irbuf;
> +             struct xfs_inobt_rec_incore     *irbufend = irbuf + nirbuf;
> +             bool                            end_of_ag = false;
> +             int                             icount = 0;
> +             int                             stat;
> +
> +             error = xfs_ialloc_read_agi(mp, NULL, agno, &agbp);
> +             if (error)
> +                     break;
> +
> +             /*
> +              * Allocate and initialize a btree cursor for ialloc btree.
> +              */
> +             cur = xfs_inobt_init_cursor(mp, NULL, agbp, agno,
> +                                         XFS_BTNUM_INO);
> +
> +             if (agino > 0) {
> +                     /*
> +                      * In the middle of an allocation group, we need to get
> +                      * the remainder of the chunk we are in.
> +                      */
> +                     struct xfs_inobt_rec_incore     r;
> +
> +                     error = xfs_bulkstat_grab_ichunk(cur, agino, &icount, 
> &r);
> +                     if (error)
> +                             goto del_cursor;
> +                     if (icount) {
> +                             irbp->ir_startino = r.ir_startino;
> +                             irbp->ir_freecount = r.ir_freecount;
> +                             irbp->ir_free = r.ir_free;
> +                             irbp++;
> +                     }
> +                     /* Increment to the next record */
> +                     error = xfs_btree_increment(cur, 0, &stat);
> +             } else {
> +                     /* Start of ag. Lookup the first inode chunk */
> +                     error = xfs_inobt_lookup(cur, 0, XFS_LOOKUP_GE, &stat);
> +             }
> +             if (error || stat == 0) {
> +                     end_of_ag = true;
> +                     goto del_cursor;
> +             }
> +
> +             /*
> +              * Loop through inode btree records in this ag,
> +              * until we run out of inodes or space in the buffer.
> +              */
> +             while (irbp < irbufend && icount < ubcount) {
> +                     struct xfs_inobt_rec_incore     r;
> +
> +                     error = xfs_inobt_get_rec(cur, &r, &stat);
> +                     if (error || stat == 0) {
> +                             end_of_ag = true;
> +                             goto del_cursor;
> +                     }
> +
> +                     /*
> +                      * If this chunk has any allocated inodes, save it.
> +                      * Also start read-ahead now for this chunk.
> +                      */
> +                     if (r.ir_freecount < XFS_INODES_PER_CHUNK) {
> +                             xfs_bulkstat_ichunk_ra(mp, agno, &r);
> +                             irbp->ir_startino = r.ir_startino;
> +                             irbp->ir_freecount = r.ir_freecount;
> +                             irbp->ir_free = r.ir_free;
> +                             irbp++;
> +                             icount += XFS_INODES_PER_CHUNK - r.ir_freecount;
> +                     }
> +                     error = xfs_btree_increment(cur, 0, &stat);
> +                     if (error || stat == 0) {
> +                             end_of_ag = true;
> +                             goto del_cursor;
> +                     }
> +                     cond_resched();
> +             }
> +
> +     /*
> +      * Drop the btree buffers and the agi buffer as we can't hold any of the
> +      * locks these represent when calling iget. If there is a pending error,
> +      * then we are done.
> +      */

odd indenting?

> +del_cursor:
> +             xfs_btree_del_cursor(cur, XFS_BTREE_NOERROR);
> +             xfs_buf_relse(agbp);
> +             if (error)
> +                     break;
> +             /*
> +              * Now format all the good inodes into the user's buffer. The
> +              * call to xfs_bulkstat_ag_ichunk() sets up the agino pointer
> +              * for the next loop iteration.
> +              */
> +             irbufend = irbp;
> +             for (irbp = irbuf;
> +                  irbp < irbufend && ac.ac_ubleft >= statstruct_size;
> +                  irbp++) {
> +                     error = xfs_bulkstat_ag_ichunk(mp, agno, irbp, 
> formatter,
> +                                             statstruct_size, &ac, &agino);
> +                     if (error)
> +                             break;
> +
> +                     cond_resched();
> +             }
> +
> +             /*
> +              * If we have run out of space or had a formatting error, we
> +              * are now done
> +              */
> +             if (ac.ac_ubleft < statstruct_size || error)
> +                     break;
> +
> +             if (end_of_ag) {
> +                     agno++;
> +                     agino = 0;
> +             }
> +     }
> +     /*
> +      * Done, we are either out of specified inode range or space to
> +      * put the data.
> +      */
> +     kmem_free(irbuf);
> +     *ubcountp = ac.ac_ubelem;
> +
> +     /*
> +      * We found some inodes, so clear the error status and return them.
> +      * The lastino pointer will point directly at the inode that triggered
> +      * any error that occurred, so on the next call the error will be
> +      * triggered again and propagated to userspace as there will be no
> +      * formatted inodes in the buffer.
> +      */
> +     if (ac.ac_ubelem)
> +             error = 0;
> +
> +     /*
> +      * If we ran out of specified range, lastino will point off the end of
> +      * the file range, so, the next call will return immediately.
> +      */
> +     *lastinop = XFS_AGINO_TO_INO(mp, agno, agino);
> +     if (agno >= end)
> +             *done = 1;
> +
> +     return error;
> +}
> +
>  int
>  xfs_inumbers_fmt(
>       void                    __user *ubuffer, /* buffer to write to */
> diff --git a/fs/xfs/xfs_itable.h b/fs/xfs/xfs_itable.h
> index 6ea8b39..f8cf724 100644
> --- a/fs/xfs/xfs_itable.h
> +++ b/fs/xfs/xfs_itable.h
> @@ -50,6 +50,22 @@ xfs_bulkstat(
>       char            __user *ubuffer,/* buffer with inode stats */
>       int             *done);         /* 1 if there are more stats to get */
>  
> +/*
> + * Return stat information in bulk (by-inode) for the ispecified
> + * filesystem range.
> + */
> +int
> +xfs_bulkstat_range(
> +     xfs_mount_t     *mp,            /* mount point for filesystem */
> +     xfs_ino_t       *lastinop,      /* last inode returned */
> +     int             *ubcountp,      /* size of buffer/count returned */
> +     bulkstat_one_pf formatter,      /* func that'd fill a single buf */
> +     size_t          statstruct_size,/* sizeof struct filling */
> +     char            __user *ubuffer,/* buffer with inode stats */
> +     __u64           start,          /* start bulkstat here */
> +     __u64           end,            /* end bulkstat here */
> +     int             *done);         /* 1 if there are more stats to get */
> +
>  typedef int (*bulkstat_one_fmt_pf)(  /* used size in bytes or negative error 
> */
>       void                    __user *ubuffer, /* buffer to write to */
>       int                     ubsize,          /* remaining user buffer sz */
> 

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