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Re: [PATCH v2 2/10] xfs: Add support FALLOC_FL_INSERT_RANGE for fallocat

To: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
Subject: Re: [PATCH v2 2/10] xfs: Add support FALLOC_FL_INSERT_RANGE for fallocate
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Fri, 9 May 2014 11:24:41 -0400
Cc: "'Dave Chinner'" <david@xxxxxxxxxxxxx>, "'Theodore Ts'o'" <tytso@xxxxxxx>, linux-fsdevel@xxxxxxxxxxxxxxx, "'linux-ext4'" <linux-ext4@xxxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, "'Ashish Sangwan'" <a.sangwan@xxxxxxxxxxx>, xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <003801cf6aa7$f1f87b70$d5e97250$@samsung.com>
References: <003801cf6aa7$f1f87b70$d5e97250$@samsung.com>
User-agent: Mutt/1.5.21 (2010-09-15)
On Thu, May 08, 2014 at 07:26:16PM +0900, Namjae Jeon wrote:
> This patch implements fallocate's FALLOC_FL_INSERT_RANGE for XFS.
> 
> 1) Make sure that both offset and len are block size aligned.
> 2) Update the i_size of inode by len bytes.
> 3) Compute the file's logical block number against offset. If the computed
>    block number is not the starting block of the extent, split the extent
>    such that the block number is the starting block of the extent.
> 4) Shift all the extents which are lying bewteen [offset, last allocated 
> extent]
>    towards right by len bytes. This step will make a hole of len bytes
>    at offset.
> 5) Allocate unwritten extents for the hole created in step 4.
> 
> Signed-off-by: Namjae Jeon <namjae.jeon@xxxxxxxxxxx>
> Signed-off-by: Ashish Sangwan <a.sangwan@xxxxxxxxxxx>
> ---
>  fs/xfs/xfs_bmap.c      | 372 
> ++++++++++++++++++++++++++++++++++++++++++++++++-
>  fs/xfs/xfs_bmap.h      |   9 +-
>  fs/xfs/xfs_bmap_util.c | 129 ++++++++++++++++-
>  fs/xfs/xfs_bmap_util.h |   2 +
>  fs/xfs/xfs_file.c      |  37 ++++-
>  fs/xfs/xfs_trace.h     |   1 +
>  6 files changed, 545 insertions(+), 5 deletions(-)
> 
> diff --git a/fs/xfs/xfs_bmap.c b/fs/xfs/xfs_bmap.c
> index 1ff0da6..e24aa14 100644
> --- a/fs/xfs/xfs_bmap.c
> +++ b/fs/xfs/xfs_bmap.c
> @@ -5419,7 +5419,7 @@ error0:
>   * into, this will be considered invalid operation and we abort immediately.
>   */
>  int
> -xfs_bmap_shift_extents(
> +xfs_bmap_shift_extents_left(
>       struct xfs_trans        *tp,
>       struct xfs_inode        *ip,
>       int                     *done,
> @@ -5449,7 +5449,7 @@ xfs_bmap_shift_extents(
>           (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
>            XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
>            mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
> -             XFS_ERROR_REPORT("xfs_bmap_shift_extents",
> +             XFS_ERROR_REPORT("xfs_bmap_shift_extents_left",
>                                XFS_ERRLEVEL_LOW, mp);
>               return XFS_ERROR(EFSCORRUPTED);
>       }
> @@ -5606,3 +5606,371 @@ del_cursor:
>       xfs_trans_log_inode(tp, ip, logflags);
>       return error;
>  }
> +
> +/*
> + * Splits an extent into two extents at split_fsb block that it is
> + * the first block of the current_ext. @current_ext is a target extent
> + * to be splitted. @split_fsb is a block where the extents is spliited.
> + * If split_fsb lies in a hole or the first block of extents, just return 0.
> + */
> +STATIC int
> +xfs_bmap_split_extent_at(
> +     struct xfs_trans        *tp,
> +     struct xfs_inode        *ip,
> +     xfs_fileoff_t           split_fsb,
> +     xfs_extnum_t            *current_ext,
> +     xfs_fsblock_t           *firstfsb,
> +     struct xfs_bmap_free    *free_list)
> +{
> +     int                             whichfork = XFS_DATA_FORK;
> +     struct xfs_btree_cur            *cur;
> +     struct xfs_bmbt_rec_host        *gotp;
> +     struct xfs_bmbt_irec            got;
> +     struct xfs_bmbt_irec            new; /* splitted extent */
> +     struct xfs_mount                *mp = ip->i_mount;
> +     struct xfs_ifork                *ifp;
> +     xfs_fsblock_t                   gotblkcnt; /* new block count for got */
> +     int                             error = 0;
> +     int                             logflags;
> +     int                             i = 0;
> +
> +     if (unlikely(XFS_TEST_ERROR(
> +         (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
> +          XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
> +          mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
> +             XFS_ERROR_REPORT("xfs_bmap_split_extent_at",
> +                              XFS_ERRLEVEL_LOW, mp);
> +             return XFS_ERROR(EFSCORRUPTED);
> +     }
> +
> +     if (XFS_FORCED_SHUTDOWN(mp))
> +             return XFS_ERROR(EIO);
> +
> +     ASSERT(current_ext != NULL);
> +
> +     ifp = XFS_IFORK_PTR(ip, whichfork);
> +     if (!(ifp->if_flags & XFS_IFEXTENTS)) {
> +             /* Read in all the extents */
> +             error = xfs_iread_extents(tp, ip, whichfork);
> +             if (error)
> +                     return error;
> +     }
> +
> +     gotp = xfs_iext_bno_to_ext(ifp, split_fsb, current_ext);
> +     /*
> +      * gotp can be null in 2 cases: 1) if there are no extents
> +      * or 2) split_fsb lies in a hole beyond which there are
> +      * no extents. Either way, we are done.
> +      */
> +     if (!gotp)
> +             return 0;
> +
> +     xfs_bmbt_get_all(gotp, &got);
> +
> +     /*
> +      * Check split_fsb lies in a hole or the start boundary offset
> +      * of the extent.
> +      */
> +     if (got.br_startoff >= split_fsb)
> +             return 0;
> +
> +     gotblkcnt = split_fsb - got.br_startoff;
> +     new.br_startoff = split_fsb;
> +     new.br_startblock = got.br_startblock + gotblkcnt;
> +     new.br_blockcount = got.br_blockcount - gotblkcnt;
> +     new.br_state = got.br_state;
> +
> +     /* We are going to change core inode */
> +     logflags = XFS_ILOG_CORE;
> +
> +     if (ifp->if_flags & XFS_IFBROOT) {
> +             cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
> +             cur->bc_private.b.firstblock = *firstfsb;
> +             cur->bc_private.b.flist = free_list;
> +             cur->bc_private.b.flags = 0;
> +     } else {
> +             cur = NULL;
> +             logflags |= XFS_ILOG_DEXT;
> +     }
> +
> +     if (cur) {
> +             error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
> +                                        got.br_startblock,
> +                                        got.br_blockcount,
> +                                        &i);
> +             if (error)
> +                     goto del_cursor;
> +             XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> +     }
> +
> +     xfs_bmbt_set_blockcount(gotp, gotblkcnt);
> +     got.br_blockcount = gotblkcnt;
> +     if (cur) {
> +             error = xfs_bmbt_update(cur, got.br_startoff,
> +                                     got.br_startblock,
> +                                     got.br_blockcount,
> +                                     got.br_state);
> +             if (error)
> +                     goto del_cursor;
> +     }
> +
> +     /* Add new extent */
> +     (*current_ext)++;
> +     xfs_iext_insert(ip, *current_ext, 1, &new, 0);
> +     XFS_IFORK_NEXT_SET(ip, whichfork,
> +             XFS_IFORK_NEXTENTS(ip, whichfork) + 1);
> +
> +     if (cur) {
> +             error = xfs_bmbt_lookup_eq(cur, new.br_startoff,
> +                                        new.br_startblock, new.br_blockcount,
> +                                        &i);
> +             if (error)
> +                     goto del_cursor;
> +             XFS_WANT_CORRUPTED_GOTO(i == 0, del_cursor);
> +             cur->bc_rec.b.br_state = new.br_state;
> +
> +             error = xfs_btree_insert(cur, &i);
> +             if (error)
> +                     goto del_cursor;
> +             XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> +     }
> +
> +     /*
> +      * Convert to a btree if necessary.
> +      */
> +     if (xfs_bmap_needs_btree(ip, whichfork)) {
> +             int tmp_logflags; /* partial log flag return val */
> +
> +             ASSERT(cur == NULL);
> +             error = xfs_bmap_extents_to_btree(tp, ip, firstfsb, free_list,
> +                             &cur, 0, &tmp_logflags, whichfork);
> +             logflags |= tmp_logflags;
> +     }
> +
> +del_cursor:
> +     if (cur)
> +             xfs_btree_del_cursor(cur,
> +                     error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
> +     xfs_trans_log_inode(tp, ip, logflags);
> +     return error;
> +}
> +
> +int
> +xfs_bmap_split_extent(
> +     struct xfs_inode        *ip,
> +     xfs_fileoff_t           split_fsb,
> +     xfs_extnum_t            *split_ext)
> +{
> +     struct xfs_mount        *mp = ip->i_mount;
> +     struct xfs_trans        *tp;
> +     struct xfs_bmap_free    free_list;
> +     xfs_fsblock_t           firstfsb;
> +     int                     committed;
> +     int                     error;
> +
> +     tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
> +     error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
> +                     XFS_DIOSTRAT_SPACE_RES(mp, 0), 0);
> +
> +     if (error) {
> +             /*
> +              * Free the transaction structure.
> +              */
> +             ASSERT(XFS_FORCED_SHUTDOWN(mp));

As in the other patch, we're attempting to reserve fs blocks for the
transaction, so ENOSPC is a possibility that I think the assert should
accommodate.

> +             xfs_trans_cancel(tp, 0);
> +             return error;
> +     }
> +
> +     xfs_ilock(ip, XFS_ILOCK_EXCL);
> +     error = xfs_trans_reserve_quota(tp, mp, ip->i_udquot,
> +                     ip->i_gdquot, ip->i_pdquot,
> +                     XFS_DIOSTRAT_SPACE_RES(mp, 0), 0,
> +                     XFS_QMOPT_RES_REGBLKS);
> +     if (error)
> +             goto error1;
> +
> +     xfs_trans_ijoin(tp, ip, 0);
> +     xfs_bmap_init(&free_list, &firstfsb);
> +
> +     error = xfs_bmap_split_extent_at(tp, ip, split_fsb, split_ext,
> +                                      &firstfsb, &free_list);
> +     if (error)
> +             goto error0;
> +
> +     error = xfs_bmap_finish(&tp, &free_list, &committed);
> +     if (error)
> +             goto error0;
> +
> +     error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
> +     xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +
> +     return error;
> +error0:
> +     xfs_bmap_cancel(&free_list);
> +error1:
> +     xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
> +     xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +     return error;
> +}
> +
> +/*
> + * Shift extent records to the right to make a hole.
> + * The maximum number of extents to be shifted in a single operation
> + * is @num_exts, and @current_ext keeps track of the current extent
> + * index we have shifted. @offset_shift_fsb is the length by which each
> + * extent is shifted. @end_ext is the last extent to be shifted.
> + */
> +int
> +xfs_bmap_shift_extents_right(
> +     struct xfs_trans        *tp,
> +     struct xfs_inode        *ip,
> +     int                     *done,
> +     xfs_fileoff_t           offset_shift_fsb,
> +     xfs_extnum_t            *current_ext,
> +     xfs_extnum_t            end_ext,
> +     xfs_fsblock_t           *firstblock,
> +     struct xfs_bmap_free    *flist,
> +     int                     num_exts)
> +{
> +     struct xfs_mount                *mp = ip->i_mount;
> +     struct xfs_btree_cur            *cur;
> +     struct xfs_bmbt_rec_host        *gotp;
> +     struct xfs_bmbt_irec            got;
> +     struct xfs_bmbt_irec            right;
> +     xfs_ifork_t                     *ifp;
> +     xfs_fileoff_t                   startoff;
> +     xfs_filblks_t                   blockcount = 0;
> +     xfs_extnum_t                    last_extent;
> +     int                             error = 0;
> +     int                             i;
> +     int                             whichfork = XFS_DATA_FORK;
> +     int                             logflags;
> +
> +     if (unlikely(XFS_TEST_ERROR(
> +         (XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_EXTENTS &&
> +          XFS_IFORK_FORMAT(ip, whichfork) != XFS_DINODE_FMT_BTREE),
> +          mp, XFS_ERRTAG_BMAPIFORMAT, XFS_RANDOM_BMAPIFORMAT))) {
> +             XFS_ERROR_REPORT("xfs_bmap_shift_extents_right",
> +                              XFS_ERRLEVEL_LOW, mp);
> +             return XFS_ERROR(EFSCORRUPTED);
> +     }
> +
> +     if (XFS_FORCED_SHUTDOWN(mp))
> +             return XFS_ERROR(EIO);
> +
> +     ASSERT(current_ext != NULL);
> +
> +     /* We are going to change core inode */
> +     logflags = XFS_ILOG_CORE;
> +     ifp = XFS_IFORK_PTR(ip, whichfork);
> +
> +     if (ifp->if_flags & XFS_IFBROOT) {
> +             cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
> +             cur->bc_private.b.firstblock = *firstblock;
> +             cur->bc_private.b.flist = flist;
> +             cur->bc_private.b.flags = 0;
> +     } else {
> +             cur = NULL;
> +             logflags |= XFS_ILOG_DEXT;
> +     }
> +
> +     /* start shifting extents to right */
> +     while (num_exts-- > 0) {
> +             blockcount = 0;
> +
> +             if (*current_ext < end_ext) {
> +                     *done = 1;
> +                     break;
> +             }
> +
> +             gotp = xfs_iext_get_ext(ifp, *current_ext);
> +             xfs_bmbt_get_all(gotp, &got);
> +             startoff = got.br_startoff + offset_shift_fsb;
> +
> +             /*
> +              * Before shifting extent into hole, make sure that the hole
> +              * is large enough to accomodate the shift. This checking has
> +              * to be performed for all except the last extent.
> +              */
> +             last_extent = (ifp->if_bytes / sizeof(xfs_bmbt_rec_t)) - 1;
> +             if (last_extent != *current_ext) {
> +                     xfs_bmbt_get_all(xfs_iext_get_ext(ifp,
> +                                             *current_ext + 1), &right);
> +                     if (startoff + got.br_blockcount > right.br_startoff) {
> +                             error = XFS_ERROR(EINVAL);
> +                             if (error)
> +                                     goto del_cursor;
> +                     }
> +             }
> +
> +             /* Check if we can merge 2 adjacent extents */
> +             if (last_extent != *current_ext &&
> +                 right.br_startoff == startoff + got.br_blockcount &&
> +                 right.br_startblock ==
> +                             got.br_startblock + got.br_blockcount &&
> +                 right.br_state == got.br_state &&
> +                 right.br_blockcount + got.br_blockcount <= MAXEXTLEN) {
> +                     blockcount = right.br_blockcount + got.br_blockcount;
> +
> +                     /* Make cursor point to the extent we will update */

The comment could be more clear about what we're doing in this case. For
example:

/*
 * Merge the current extent with the extent to the right. Remove the right
 * extent, calculate a new block count for the current extent to cover the range
 * of both and decrement the number of extents in the fork.
 */

I'd also move the comment before the blockcount calculation.

> +                     if (cur) {
> +                             error = xfs_bmbt_lookup_eq(cur,
> +                                                        right.br_startoff,
> +                                                        right.br_startblock,
> +                                                        right.br_blockcount,
> +                                                        &i);
> +                             if (error)
> +                                     goto del_cursor;
> +                             XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> +                     }
> +
> +                     xfs_iext_remove(ip, *current_ext + 1, 1, 0);
> +                     if (cur) {
> +                             error = xfs_btree_delete(cur, &i);
> +                             if (error)
> +                                     goto del_cursor;
> +                             XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> +                     }
> +                     XFS_IFORK_NEXT_SET(ip, whichfork,
> +                                     XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
> +
> +             }
> +
> +             if (cur) {
> +                     error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
> +                                                got.br_startblock,
> +                                                got.br_blockcount,
> +                                                &i);
> +                     if (error)
> +                             goto del_cursor;
> +                     XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
> +             }
> +
> +             if (got.br_blockcount < blockcount) {
> +                     xfs_bmbt_set_blockcount(gotp, blockcount);
> +                     got.br_blockcount = blockcount;
> +             }

How about just 'if (blockcount)' so the algorithm is clear?

> +
> +
> +             xfs_bmbt_set_startoff(gotp, startoff);
> +             got.br_startoff = startoff;
> +
> +             if (cur) {
> +                     error = xfs_bmbt_update(cur, got.br_startoff,
> +                                             got.br_startblock,
> +                                             got.br_blockcount,
> +                                             got.br_state);
> +                     if (error)
> +                             goto del_cursor;
> +             }
> +
> +             (*current_ext)--;
> +     }
> +
> +del_cursor:
> +     if (cur)
> +             xfs_btree_del_cursor(cur,
> +                     error ? XFS_BTREE_ERROR : XFS_BTREE_NOERROR);
> +     xfs_trans_log_inode(tp, ip, logflags);
> +     return error;
> +}
> diff --git a/fs/xfs/xfs_bmap.h b/fs/xfs/xfs_bmap.h
> index 38ba36e..af05899 100644
> --- a/fs/xfs/xfs_bmap.h
> +++ b/fs/xfs/xfs_bmap.h
> @@ -179,10 +179,17 @@ int     xfs_bunmapi(struct xfs_trans *tp, struct 
> xfs_inode *ip,
>  int  xfs_check_nostate_extents(struct xfs_ifork *ifp, xfs_extnum_t idx,
>               xfs_extnum_t num);
>  uint xfs_default_attroffset(struct xfs_inode *ip);
> -int  xfs_bmap_shift_extents(struct xfs_trans *tp, struct xfs_inode *ip,
> +int  xfs_bmap_shift_extents_left(struct xfs_trans *tp, struct xfs_inode *ip,
>               int *done, xfs_fileoff_t start_fsb,
>               xfs_fileoff_t offset_shift_fsb, xfs_extnum_t *current_ext,
>               xfs_fsblock_t *firstblock, struct xfs_bmap_free *flist,
>               int num_exts);
> +int  xfs_bmap_split_extent(struct xfs_inode *ip, xfs_fileoff_t split_offset,
> +             xfs_extnum_t *split_ext);
> +int  xfs_bmap_shift_extents_right(struct xfs_trans *tp, struct xfs_inode *ip,
> +             int *done, xfs_fsblock_t offset_shift_fsb,
> +             xfs_extnum_t *current_ext, xfs_extnum_t end_ext,
> +             xfs_fsblock_t *firstblock, struct xfs_bmap_free *flist,
> +             int num_exts);
>  
>  #endif       /* __XFS_BMAP_H__ */
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 296160b..5a56f5b 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1550,7 +1550,7 @@ xfs_collapse_file_space(
>                * We are using the write transaction in which max 2 bmbt
>                * updates are allowed
>                */
> -             error = xfs_bmap_shift_extents(tp, ip, &done, start_fsb,
> +             error = xfs_bmap_shift_extents_left(tp, ip, &done, start_fsb,
>                                              shift_fsb, &current_ext,
>                                              &first_block, &free_list,
>                                              XFS_BMAP_MAX_SHIFT_EXTENTS);
> @@ -1574,6 +1574,133 @@ out:
>  }
>  
>  /*
> + * xfs_insert_file_space()
> + *   This routine allocate disk space and shift extent for the given file.
> + *   The first thing we do is to sync dirty data and invalidate page cache
> + *   over the region on which insert range is working. And split an extent
> + *   to two extents at given offset by calling xfs_bmap_split_extent.
> + *   And shift all extent records which are laying between [offset,
> + *   last allocated extent] to the right to reserve hole range. Lastly
> + *   allocate an unwritten extent in hole range created by shifting extents.
> + *
> + * RETURNS:
> + *   0 on success
> + *   errno on error
> + *
> + */
> +int
> +xfs_insert_file_space(
> +     struct xfs_inode        *ip,
> +     loff_t                  offset,
> +     loff_t                  len)
> +{
> +     struct xfs_mount        *mp = ip->i_mount;
> +     struct xfs_trans        *tp;
> +     struct xfs_bmap_free    free_list;
> +     xfs_fsblock_t           first_block;
> +     xfs_ifork_t             *ifp;
> +     int                     done = 0;
> +     int                     committed;
> +     int                     error;
> +     uint                    rounding;
> +     xfs_fileoff_t           start_fsb;
> +     xfs_fileoff_t           shift_fsb;
> +     xfs_extnum_t            split_ext;
> +     xfs_extnum_t            current_ext = 0;
> +     xfs_off_t               ioffset;
> +
> +     ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
> +     trace_xfs_insert_file_space(ip);
> +
> +     error = xfs_qm_dqattach(ip, 0);
> +     if (error)
> +             return error;
> +
> +     /* wait for the completion of any pending DIOs */
> +     inode_dio_wait(VFS_I(ip));
> +
> +     rounding = max_t(uint, 1 << mp->m_sb.sb_blocklog, PAGE_CACHE_SIZE);
> +     ioffset = offset & ~(rounding - 1);
> +     error = -filemap_write_and_wait_range(VFS_I(ip)->i_mapping,
> +                     ioffset, -1);
> +     if (error)
> +             return error;
> +
> +     truncate_pagecache_range(VFS_I(ip), ioffset, -1);
> +
> +     start_fsb = XFS_B_TO_FSB(mp, offset);
> +     shift_fsb = XFS_B_TO_FSB(mp, len);
> +
> +     error = xfs_bmap_split_extent(ip, start_fsb, &split_ext);
> +     if (error)
> +             return error;
> +
> +     ifp = XFS_IFORK_PTR(ip, XFS_DATA_FORK);
> +     current_ext = (ifp->if_bytes / sizeof(xfs_bmbt_rec_t)) - 1;
> +     while (!error && !done) {
> +             tp = xfs_trans_alloc(mp, XFS_TRANS_DIOSTRAT);
> +             /*
> +              * We would need to reserve permanent block for transaction.
> +              * This will come into picture when after shifting extent into
> +              * hole we found that adjacent extents can be merged which
> +              * may lead to freeing of a block during record update.
> +              */
> +             error = xfs_trans_reserve(tp, &M_RES(mp)->tr_write,
> +                             XFS_DIOSTRAT_SPACE_RES(mp, 0), 0);
> +             if (error) {
> +                     ASSERT(error == ENOSPC || XFS_FORCED_SHUTDOWN(mp));
> +                     xfs_trans_cancel(tp, 0);
> +                     break;
> +             }
> +
> +             xfs_ilock(ip, XFS_ILOCK_EXCL);
> +             error = xfs_trans_reserve_quota(tp, mp, ip->i_udquot,
> +                             ip->i_gdquot, ip->i_pdquot,
> +                             XFS_DIOSTRAT_SPACE_RES(mp, 0), 0,
> +                             XFS_QMOPT_RES_REGBLKS);
> +             if (error)
> +                     goto error1;
> +
> +             xfs_trans_ijoin(tp, ip, 0);
> +
> +             xfs_bmap_init(&free_list, &first_block);
> +
> +             /*
> +              * We are using the write transaction in which max 2 bmbt
> +              * updates are allowed
> +              */
> +             error = xfs_bmap_shift_extents_right(tp, ip, &done, shift_fsb,
> +                                             &current_ext, split_ext,
> +                                             &first_block, &free_list,
> +                                             XFS_BMAP_MAX_SHIFT_EXTENTS);
> +             if (error)
> +                     goto error0;
> +
> +             error = xfs_bmap_finish(&tp, &free_list, &committed);
> +             if (error)
> +                     goto error0;
> +
> +             error = xfs_trans_commit(tp, XFS_TRANS_RELEASE_LOG_RES);
> +             xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +             if (error)
> +                     goto out;
> +     }
> +
> +     /* Add unwritten extent in a hole range. */
> +     error = xfs_alloc_file_space(ip, offset, len, XFS_BMAPI_PREALLOC);
> +
> +out:
> +     return error;
> +
> +error0:
> +     xfs_bmap_cancel(&free_list);
> +error1:
> +     xfs_trans_cancel(tp, XFS_TRANS_RELEASE_LOG_RES | XFS_TRANS_ABORT);
> +     xfs_iunlock(ip, XFS_ILOCK_EXCL);
> +     return error;
> +}
> +
> +/*
>   * We need to check that the format of the data fork in the temporary inode 
> is
>   * valid for the target inode before doing the swap. This is not a problem 
> with
>   * attr1 because of the fixed fork offset, but attr2 has a dynamically sized
> diff --git a/fs/xfs/xfs_bmap_util.h b/fs/xfs/xfs_bmap_util.h
> index 935ed2b..d62ab4b 100644
> --- a/fs/xfs/xfs_bmap_util.h
> +++ b/fs/xfs/xfs_bmap_util.h
> @@ -101,6 +101,8 @@ int       xfs_zero_file_space(struct xfs_inode *ip, 
> xfs_off_t offset,
>                           xfs_off_t len);
>  int  xfs_collapse_file_space(struct xfs_inode *, xfs_off_t offset,
>                               xfs_off_t len);
> +int  xfs_insert_file_space(struct xfs_inode *, xfs_off_t offset,
> +                             xfs_off_t len);
>  
>  /* EOF block manipulation functions */
>  bool xfs_can_free_eofblocks(struct xfs_inode *ip, bool force);
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 97855c5..392b029 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -760,7 +760,8 @@ xfs_file_fallocate(
>       if (!S_ISREG(inode->i_mode))
>               return -EINVAL;
>       if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE |
> -                  FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE))
> +                  FALLOC_FL_COLLAPSE_RANGE | FALLOC_FL_ZERO_RANGE |
> +                  FALLOC_FL_INSERT_RANGE))
>               return -EOPNOTSUPP;
>  
>       xfs_ilock(ip, XFS_IOLOCK_EXCL);
> @@ -790,6 +791,40 @@ xfs_file_fallocate(
>               error = xfs_collapse_file_space(ip, offset, len);
>               if (error)
>                       goto out_unlock;
> +     } else if (mode & FALLOC_FL_INSERT_RANGE) {
> +             unsigned blksize_mask = (1 << inode->i_blkbits) - 1;
> +             struct iattr iattr;
> +
> +             if (offset & blksize_mask || len & blksize_mask) {
> +                     error = -EINVAL;
> +                     goto out_unlock;
> +             }
> +
> +             /* Check for wrap through zero */
> +             if (inode->i_size + len > inode->i_sb->s_maxbytes) {
> +                     error = -EFBIG;
> +                     goto out_unlock;
> +             }
> +
> +             /* Offset should be less than i_size */
> +             if (offset >= i_size_read(inode)) {
> +                     error = -EINVAL;
> +                     goto out_unlock;
> +             }
> +
> +             /*
> +              * The first thing we do is to expand file to
> +              * avoid data loss if there is error while shifting
> +              */
> +             iattr.ia_valid = ATTR_SIZE;
> +             iattr.ia_size = i_size_read(inode) + len;
> +             error = xfs_setattr_size(ip, &iattr);
> +             if (error)
> +                     goto out_unlock;

I don't necessarily know that it's problematic to do the setattr before
the bmap fixup. We'll have a chance for partial completion of this
operation either way. But I'm not a fan of the code duplication here.
This also still skips the time update in the event of insert space
failure, though perhaps that's not such a big deal if we're returning an
error.

I think it would be better to leave things organized as before and
introduce an error2 variable and a &nrshifts or some such parameter to
xfs_insert_file_space() that initializes to 0 and returns the number of
record shifts. The caller can then decide whether it's appropriate to
break out immediately or do the inode size update and return the error.

Perhaps not the cleanest thing in the world, but also not the first
place we would use 'error2' to manage error priorities (grep around for
it)...

Brian

> +
> +             error = xfs_insert_file_space(ip, offset, len);
> +             if (error)
> +                     goto out_unlock;
>       } else {
>               if (!(mode & FALLOC_FL_KEEP_SIZE) &&
>                   offset + len > i_size_read(inode)) {
> diff --git a/fs/xfs/xfs_trace.h b/fs/xfs/xfs_trace.h
> index 152f827..8943c9f 100644
> --- a/fs/xfs/xfs_trace.h
> +++ b/fs/xfs/xfs_trace.h
> @@ -663,6 +663,7 @@ DEFINE_INODE_EVENT(xfs_alloc_file_space);
>  DEFINE_INODE_EVENT(xfs_free_file_space);
>  DEFINE_INODE_EVENT(xfs_zero_file_space);
>  DEFINE_INODE_EVENT(xfs_collapse_file_space);
> +DEFINE_INODE_EVENT(xfs_insert_file_space);
>  DEFINE_INODE_EVENT(xfs_readdir);
>  #ifdef CONFIG_XFS_POSIX_ACL
>  DEFINE_INODE_EVENT(xfs_get_acl);
> -- 
> 1.7.11-rc0
> 
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