[XFS] 929045 567344 This mod introduces multi-level in-core file extent

functionality, building upon the new layout introduced in mod
xfs-linux:xfs-kern:207390a.  The new multi-level extent allocations are
only required for heavily fragmented files, so the old-style linear extent
list is used on files until the extents reach a pre-determined size of 4k.
4k buffers are used because this is the system page size on Linux i386 and
systems with larger page sizes don't seem to gain much, if anything, by
using their native page size as the extent buffer size. Also, using 4k
extent buffers everywhere provides a consistent interface for CXFS across
different platforms.  The 4k extent buffers are managed by an indirection
array (xfs_ext_irec_t) which is basically just a pointer array with a bit
of extra information to keep track of the number of extents in each buffer
as well as the extent offset of each buffer.  Major changes include:  -
Add multi-level in-core file extent functionality to the xfs_iext_  
subroutines introduced in mod:	xfs-linux:xfs-kern:207390a  - Introduce 13
new subroutines which add functionality for multi-level   in-core file
extents:	 xfs_iext_add_indirect_multi()	      
xfs_iext_remove_indirect()	   xfs_iext_realloc_indirect()	      
xfs_iext_indirect_to_direct()	      xfs_iext_bno_to_irec()	    
xfs_iext_idx_to_irec()	       xfs_iext_irec_init()	   
xfs_iext_irec_new()	    xfs_iext_irec_remove()	  
xfs_iext_irec_compact() 	xfs_iext_irec_compact_pages()	     
xfs_iext_irec_compact_full()	     xfs_iext_irec_update_extoffs()

SGI-PV: 928864
SGI-Modid: xfs-linux-melb:xfs-kern:207393a

Signed-off-by: Mandy Kirkconnell <alkirkco@sgi.com>
Signed-off-by: Nathan Scott <nathans@sgi.com>

1 files changed, 710 insertions, 5 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 6459395a0e40..580fa0758039 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2630,8 +2630,9 @@ xfs_idestroy_fork(
                         ifp->if_real_bytes = 0;
                 }
         } else if ((ifp->if_flags & XFS_IFEXTENTS) &&
-                   (ifp->if_u1.if_extents != NULL) &&
-                   (ifp->if_u1.if_extents != ifp->if_u2.if_inline_ext)) {
+                   ((ifp->if_flags & XFS_IFEXTIREC) ||
+                    ((ifp->if_u1.if_extents != NULL) &&
+                     (ifp->if_u1.if_extents != ifp->if_u2.if_inline_ext)))) {
                 ASSERT(ifp->if_real_bytes != 0);
                 xfs_iext_destroy(ifp);
         }
@@ -3622,7 +3623,16 @@ xfs_iext_get_ext(
         xfs_extnum_t    idx)            /* index of target extent */
 {
         ASSERT(idx >= 0);
-        if (ifp->if_bytes) {
+        if ((ifp->if_flags & XFS_IFEXTIREC) && (idx == 0)) {
+                return ifp->if_u1.if_ext_irec->er_extbuf;
+        } else if (ifp->if_flags & XFS_IFEXTIREC) {
+                xfs_ext_irec_t  *erp;           /* irec pointer */
+                int             erp_idx = 0;    /* irec index */
+                xfs_extnum_t    page_idx = idx; /* ext index in target list */
+
+                erp = xfs_iext_idx_to_irec(ifp, &page_idx, &erp_idx, 0);
+                return &erp->er_extbuf[page_idx];
+        } else if (ifp->if_bytes) {
                 return &ifp->if_u1.if_extents[idx];
         } else {
                 return NULL;
@@ -3691,6 +3701,7 @@ xfs_iext_add(
                 }
                 ifp->if_u1.if_extents = ifp->if_u2.if_inline_ext;
                 ifp->if_real_bytes = 0;
+                ifp->if_lastex = nextents + ext_diff;
         }
         /*
          * Otherwise use a linear (direct) extent list.
@@ -3698,7 +3709,7 @@ xfs_iext_add(
          * xfs_iext_realloc_direct will switch us from
          * inline to direct extent allocation mode.
          */
-        else {
+        else if (nextents + ext_diff <= XFS_LINEAR_EXTS) {
                 xfs_iext_realloc_direct(ifp, new_size);
                 if (idx < nextents) {
                         memmove(&ifp->if_u1.if_extents[idx + ext_diff],
@@ -3707,14 +3718,182 @@ xfs_iext_add(
                         memset(&ifp->if_u1.if_extents[idx], 0, byte_diff);
                 }
         }
+        /* Indirection array */
+        else {
+                xfs_ext_irec_t  *erp;
+                int             erp_idx = 0;
+                int             page_idx = idx;
+
+                ASSERT(nextents + ext_diff > XFS_LINEAR_EXTS);
+                if (ifp->if_flags & XFS_IFEXTIREC) {
+                        erp = xfs_iext_idx_to_irec(ifp, &page_idx, &erp_idx, 1);
+                } else {
+                        xfs_iext_irec_init(ifp);
+                        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+                        erp = ifp->if_u1.if_ext_irec;
+                }
+                /* Extents fit in target extent page */
+                if (erp && erp->er_extcount + ext_diff <= XFS_LINEAR_EXTS) {
+                        if (page_idx < erp->er_extcount) {
+                                memmove(&erp->er_extbuf[page_idx + ext_diff],
+                                        &erp->er_extbuf[page_idx],
+                                        (erp->er_extcount - page_idx) *
+                                        sizeof(xfs_bmbt_rec_t));
+                                memset(&erp->er_extbuf[page_idx], 0, byte_diff);
+                        }
+                        erp->er_extcount += ext_diff;
+                        xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
+                }
+                /* Insert a new extent page */
+                else if (erp) {
+                        xfs_iext_add_indirect_multi(ifp,
+                                erp_idx, page_idx, ext_diff);
+                }
+                /*
+                 * If extent(s) are being appended to the last page in
+                 * the indirection array and the new extent(s) don't fit
+                 * in the page, then erp is NULL and erp_idx is set to
+                 * the next index needed in the indirection array.
+                 */
+                else {
+                        int     count = ext_diff;
+
+                        while (count) {
+                                erp = xfs_iext_irec_new(ifp, erp_idx);
+                                erp->er_extcount = count;
+                                count -= MIN(count, (int)XFS_LINEAR_EXTS);
+                                if (count) {
+                                        erp_idx++;
+                                }
+                        }
+                }
+        }
         ifp->if_bytes = new_size;
 }
 
 /*
+ * This is called when incore extents are being added to the indirection
+ * array and the new extents do not fit in the target extent list. The
+ * erp_idx parameter contains the irec index for the target extent list
+ * in the indirection array, and the idx parameter contains the extent
+ * index within the list. The number of extents being added is stored
+ * in the count parameter.
+ *
+ *    |-------|   |-------|
+ *    |       |   |       |    idx - number of extents before idx
+ *    |  idx  |   | count |
+ *    |       |   |       |    count - number of extents being inserted at idx
+ *    |-------|   |-------|
+ *    | count |   | nex2  |    nex2 - number of extents after idx + count
+ *    |-------|   |-------|
+ */
+void
+xfs_iext_add_indirect_multi(
+        xfs_ifork_t     *ifp,                   /* inode fork pointer */
+        int             erp_idx,                /* target extent irec index */
+        xfs_extnum_t    idx,                    /* index within target list */
+        int             count)                  /* new extents being added */
+{
+        int             byte_diff;              /* new bytes being added */
+        xfs_ext_irec_t  *erp;                   /* pointer to irec entry */
+        xfs_extnum_t    ext_diff;               /* number of extents to add */
+        xfs_extnum_t    ext_cnt;                /* new extents still needed */
+        xfs_extnum_t    nex2;                   /* extents after idx + count */
+        xfs_bmbt_rec_t  *nex2_ep = NULL;        /* temp list for nex2 extents */
+        int             nlists;                 /* number of irec's (lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        erp = &ifp->if_u1.if_ext_irec[erp_idx];
+        nex2 = erp->er_extcount - idx;
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+
+        /*
+         * Save second part of target extent list
+         * (all extents past */
+        if (nex2) {
+                byte_diff = nex2 * sizeof(xfs_bmbt_rec_t);
+                nex2_ep = (xfs_bmbt_rec_t *) kmem_alloc(byte_diff, KM_SLEEP);
+                memmove(nex2_ep, &erp->er_extbuf[idx], byte_diff);
+                erp->er_extcount -= nex2;
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, -nex2);
+                memset(&erp->er_extbuf[idx], 0, byte_diff);
+        }
+
+        /*
+         * Add the new extents to the end of the target
+         * list, then allocate new irec record(s) and
+         * extent buffer(s) as needed to store the rest
+         * of the new extents.
+         */
+        ext_cnt = count;
+        ext_diff = MIN(ext_cnt, (int)XFS_LINEAR_EXTS - erp->er_extcount);
+        if (ext_diff) {
+                erp->er_extcount += ext_diff;
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
+                ext_cnt -= ext_diff;
+        }
+        while (ext_cnt) {
+                erp_idx++;
+                erp = xfs_iext_irec_new(ifp, erp_idx);
+                ext_diff = MIN(ext_cnt, (int)XFS_LINEAR_EXTS);
+                erp->er_extcount = ext_diff;
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, ext_diff);
+                ext_cnt -= ext_diff;
+        }
+
+        /* Add nex2 extents back to indirection array */
+        if (nex2) {
+                xfs_extnum_t    ext_avail;
+                int             i;
+
+                byte_diff = nex2 * sizeof(xfs_bmbt_rec_t);
+                ext_avail = XFS_LINEAR_EXTS - erp->er_extcount;
+                i = 0;
+                /*
+                 * If nex2 extents fit in the current page, append
+                 * nex2_ep after the new extents.
+                 */
+                if (nex2 <= ext_avail) {
+                        i = erp->er_extcount;
+                }
+                /*
+                 * Otherwise, check if space is available in the
+                 * next page.
+                 */
+                else if ((erp_idx < nlists - 1) &&
+                         (nex2 <= (ext_avail = XFS_LINEAR_EXTS -
+                          ifp->if_u1.if_ext_irec[erp_idx+1].er_extcount))) {
+                        erp_idx++;
+                        erp++;
+                        /* Create a hole for nex2 extents */
+                        memmove(&erp->er_extbuf[nex2], erp->er_extbuf,
+                                erp->er_extcount * sizeof(xfs_bmbt_rec_t));
+                }
+                /*
+                 * Final choice, create a new extent page for
+                 * nex2 extents.
+                 */
+                else {
+                        erp_idx++;
+                        erp = xfs_iext_irec_new(ifp, erp_idx);
+                }
+                memmove(&erp->er_extbuf[i], nex2_ep, byte_diff);
+                kmem_free(nex2_ep, byte_diff);
+                erp->er_extcount += nex2;
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, nex2);
+        }
+}
+
+/*
  * This is called when the amount of space required for incore file
  * extents needs to be decreased. The ext_diff parameter stores the
  * number of extents to be removed and the idx parameter contains
  * the extent index where the extents will be removed from.
+ *
+ * If the amount of space needed has decreased below the linear
+ * limit, XFS_IEXT_BUFSZ, then switch to using the contiguous
+ * extent array.  Otherwise, use kmem_realloc() to adjust the
+ * size to what is needed.
  */
 void
 xfs_iext_remove(
@@ -3731,6 +3910,8 @@ xfs_iext_remove(
 
         if (new_size == 0) {
                 xfs_iext_destroy(ifp);
+        } else if (ifp->if_flags & XFS_IFEXTIREC) {
+                xfs_iext_remove_indirect(ifp, idx, ext_diff);
         } else if (ifp->if_real_bytes) {
                 xfs_iext_remove_direct(ifp, idx, ext_diff);
         } else {
@@ -3751,6 +3932,7 @@ xfs_iext_remove_inline(
 {
         int             nextents;       /* number of extents in file */
 
+        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
         ASSERT(idx < XFS_INLINE_EXTS);
         nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
         ASSERT(((nextents - ext_diff) > 0) &&
@@ -3788,6 +3970,7 @@ xfs_iext_remove_direct(
         xfs_extnum_t    nextents;       /* number of extents in file */
         int             new_size;       /* size of extents after removal */
 
+        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
         new_size = ifp->if_bytes -
                 (ext_diff * sizeof(xfs_bmbt_rec_t));
         nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
@@ -3816,6 +3999,84 @@ xfs_iext_remove_direct(
 }
 
 /*
+ * This is called when incore extents are being removed from the
+ * indirection array and the extents being removed span multiple extent
+ * buffers. The idx parameter contains the file extent index where we
+ * want to begin removing extents, and the count parameter contains
+ * how many extents need to be removed.
+ *
+ *    |-------|   |-------|
+ *    | nex1  |   |       |    nex1 - number of extents before idx
+ *    |-------|   | count |
+ *    |       |   |       |    count - number of extents being removed at idx
+ *    | count |   |-------|
+ *    |       |   | nex2  |    nex2 - number of extents after idx + count
+ *    |-------|   |-------|
+ */
+void
+xfs_iext_remove_indirect(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        xfs_extnum_t    idx,            /* index to begin removing extents */
+        int             count)          /* number of extents to remove */
+{
+        xfs_ext_irec_t  *erp;           /* indirection array pointer */
+        int             erp_idx = 0;    /* indirection array index */
+        xfs_extnum_t    ext_cnt;        /* extents left to remove */
+        xfs_extnum_t    ext_diff;       /* extents to remove in current list */
+        xfs_extnum_t    nex1;           /* number of extents before idx */
+        xfs_extnum_t    nex2;           /* extents after idx + count */
+        int             nlists;         /* entries in indirecton array */
+        int             page_idx = idx; /* index in target extent list */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        erp = xfs_iext_idx_to_irec(ifp,  &page_idx, &erp_idx, 0);
+        ASSERT(erp != NULL);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        nex1 = page_idx;
+        ext_cnt = count;
+        while (ext_cnt) {
+                nex2 = MAX((erp->er_extcount - (nex1 + ext_cnt)), 0);
+                ext_diff = MIN(ext_cnt, (erp->er_extcount - nex1));
+                /*
+                 * Check for deletion of entire list;
+                 * xfs_iext_irec_remove() updates extent offsets.
+                 */
+                if (ext_diff == erp->er_extcount) {
+                        xfs_iext_irec_remove(ifp, erp_idx);
+                        ext_cnt -= ext_diff;
+                        nex1 = 0;
+                        if (ext_cnt) {
+                                ASSERT(erp_idx < ifp->if_real_bytes /
+                                        XFS_IEXT_BUFSZ);
+                                erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                                nex1 = 0;
+                                continue;
+                        } else {
+                                break;
+                        }
+                }
+                /* Move extents up (if needed) */
+                if (nex2) {
+                        memmove(&erp->er_extbuf[nex1],
+                                &erp->er_extbuf[nex1 + ext_diff],
+                                nex2 * sizeof(xfs_bmbt_rec_t));
+                }
+                /* Zero out rest of page */
+                memset(&erp->er_extbuf[nex1 + nex2], 0, (XFS_IEXT_BUFSZ -
+                        ((nex1 + nex2) * sizeof(xfs_bmbt_rec_t))));
+                /* Update remaining counters */
+                erp->er_extcount -= ext_diff;
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1, -ext_diff);
+                ext_cnt -= ext_diff;
+                nex1 = 0;
+                erp_idx++;
+                erp++;
+        }
+        ifp->if_bytes -= count * sizeof(xfs_bmbt_rec_t);
+        xfs_iext_irec_compact(ifp);
+}
+
+/*
  * Create, destroy, or resize a linear (direct) block of extents.
  */
 void
@@ -3827,6 +4088,10 @@ xfs_iext_realloc_direct(
 
         rnew_size = new_size;
 
+        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC) ||
+                ((new_size >= 0) && (new_size <= XFS_IEXT_BUFSZ) &&
+                 (new_size != ifp->if_real_bytes)));
+
         /* Free extent records */
         if (new_size == 0) {
                 xfs_iext_destroy(ifp);
@@ -3920,13 +4185,76 @@ xfs_iext_inline_to_direct(
 }
 
 /*
+ * Resize an extent indirection array to new_size bytes.
+ */
+void
+xfs_iext_realloc_indirect(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        int             new_size)       /* new indirection array size */
+{
+        int             nlists;         /* number of irec's (ex lists) */
+        int             size;           /* current indirection array size */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        size = nlists * sizeof(xfs_ext_irec_t);
+        ASSERT(ifp->if_real_bytes);
+        ASSERT((new_size >= 0) && (new_size != size));
+        if (new_size == 0) {
+                xfs_iext_destroy(ifp);
+        } else {
+                ifp->if_u1.if_ext_irec = (xfs_ext_irec_t *)
+                        kmem_realloc(ifp->if_u1.if_ext_irec,
+                                new_size, size, KM_SLEEP);
+        }
+}
+
+/*
+ * Switch from indirection array to linear (direct) extent allocations.
+ */
+void
+xfs_iext_indirect_to_direct(
+         xfs_ifork_t    *ifp)           /* inode fork pointer */
+{
+        xfs_bmbt_rec_t  *ep;            /* extent record pointer */
+        xfs_extnum_t    nextents;       /* number of extents in file */
+        int             size;           /* size of file extents */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
+        ASSERT(nextents <= XFS_LINEAR_EXTS);
+        size = nextents * sizeof(xfs_bmbt_rec_t);
+
+        xfs_iext_irec_compact_full(ifp);
+        ASSERT(ifp->if_real_bytes == XFS_IEXT_BUFSZ);
+
+        ep = ifp->if_u1.if_ext_irec->er_extbuf;
+        kmem_free(ifp->if_u1.if_ext_irec, sizeof(xfs_ext_irec_t));
+        ifp->if_flags &= ~XFS_IFEXTIREC;
+        ifp->if_u1.if_extents = ep;
+        ifp->if_bytes = size;
+        if (nextents < XFS_LINEAR_EXTS) {
+                xfs_iext_realloc_direct(ifp, size);
+        }
+}
+
+/*
  * Free incore file extents.
  */
 void
 xfs_iext_destroy(
         xfs_ifork_t     *ifp)           /* inode fork pointer */
 {
-        if (ifp->if_real_bytes) {
+        if (ifp->if_flags & XFS_IFEXTIREC) {
+                int     erp_idx;
+                int     nlists;
+
+                nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+                for (erp_idx = nlists - 1; erp_idx >= 0 ; erp_idx--) {
+                        xfs_iext_irec_remove(ifp, erp_idx);
+                }
+                ifp->if_flags &= ~XFS_IFEXTIREC;
+        } else if (ifp->if_real_bytes) {
                 kmem_free(ifp->if_u1.if_extents, ifp->if_real_bytes);
         } else if (ifp->if_bytes) {
                 memset(ifp->if_u2.if_inline_ext, 0, XFS_INLINE_EXTS *
@@ -3936,3 +4264,380 @@ xfs_iext_destroy(
         ifp->if_real_bytes = 0;
         ifp->if_bytes = 0;
 }
+
+/*
+ * Return a pointer to the indirection array entry containing the
+ * extent record for filesystem block bno. Store the index of the
+ * target irec in *erp_idxp.
+ */
+xfs_ext_irec_t *
+xfs_iext_bno_to_irec(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        xfs_fileoff_t   bno,            /* block number to search for */
+        int             *erp_idxp)      /* irec index of target ext list */
+{
+        xfs_ext_irec_t  *erp = NULL;    /* indirection array pointer */
+        xfs_ext_irec_t  *erp_next;      /* next indirection array entry */
+        xfs_extnum_t    erp_idx;        /* indirection array index */
+        int             nlists;         /* number of extent irec's (lists) */
+        int             high;           /* binary search upper limit */
+        int             low;            /* binary search lower limit */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        erp_idx = 0;
+        low = 0;
+        high = nlists - 1;
+        while (low <= high) {
+                erp_idx = (low + high) >> 1;
+                erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                erp_next = erp_idx < nlists - 1 ? erp + 1 : NULL;
+                if (bno < xfs_bmbt_get_startoff(erp->er_extbuf)) {
+                        high = erp_idx - 1;
+                } else if (erp_next && bno >=
+                           xfs_bmbt_get_startoff(erp_next->er_extbuf)) {
+                        low = erp_idx + 1;
+                } else {
+                        break;
+                }
+        }
+        *erp_idxp = erp_idx;
+        return erp;
+}
+
+/*
+ * Return a pointer to the indirection array entry containing the
+ * extent record at file extent index *idxp. Store the index of the
+ * target irec in *erp_idxp and store the page index of the target
+ * extent record in *idxp.
+ */
+xfs_ext_irec_t *
+xfs_iext_idx_to_irec(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        xfs_extnum_t    *idxp,          /* extent index (file -> page) */
+        int             *erp_idxp,      /* pointer to target irec */
+        int             realloc)        /* new bytes were just added */
+{
+        xfs_ext_irec_t  *prev;          /* pointer to previous irec */
+        xfs_ext_irec_t  *erp = NULL;    /* pointer to current irec */
+        int             erp_idx;        /* indirection array index */
+        int             nlists;         /* number of irec's (ex lists) */
+        int             high;           /* binary search upper limit */
+        int             low;            /* binary search lower limit */
+        xfs_extnum_t    page_idx = *idxp; /* extent index in target list */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        ASSERT(page_idx >= 0 && page_idx <=
+                ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t));
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        erp_idx = 0;
+        low = 0;
+        high = nlists - 1;
+
+        /* Binary search extent irec's */
+        while (low <= high) {
+                erp_idx = (low + high) >> 1;
+                erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                prev = erp_idx > 0 ? erp - 1 : NULL;
+                if (page_idx < erp->er_extoff || (page_idx == erp->er_extoff &&
+                     realloc && prev && prev->er_extcount < XFS_LINEAR_EXTS)) {
+                        high = erp_idx - 1;
+                } else if (page_idx > erp->er_extoff + erp->er_extcount ||
+                           (page_idx == erp->er_extoff + erp->er_extcount &&
+                            !realloc)) {
+                        low = erp_idx + 1;
+                } else if (page_idx == erp->er_extoff + erp->er_extcount &&
+                           erp->er_extcount == XFS_LINEAR_EXTS) {
+                        ASSERT(realloc);
+                        page_idx = 0;
+                        erp_idx++;
+                        erp = erp_idx < nlists ? erp + 1 : NULL;
+                        break;
+                } else {
+                        page_idx -= erp->er_extoff;
+                        break;
+                }
+        }
+        *idxp = page_idx;
+        *erp_idxp = erp_idx;
+        return(erp);
+}
+
+/*
+ * Allocate and initialize an indirection array once the space needed
+ * for incore extents increases above XFS_IEXT_BUFSZ.
+ */
+void
+xfs_iext_irec_init(
+        xfs_ifork_t     *ifp)           /* inode fork pointer */
+{
+        xfs_ext_irec_t  *erp;           /* indirection array pointer */
+        xfs_extnum_t    nextents;       /* number of extents in file */
+
+        ASSERT(!(ifp->if_flags & XFS_IFEXTIREC));
+        nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
+        ASSERT(nextents <= XFS_LINEAR_EXTS);
+
+        erp = (xfs_ext_irec_t *)
+                kmem_alloc(sizeof(xfs_ext_irec_t), KM_SLEEP);
+
+        if (nextents == 0) {
+                ifp->if_u1.if_extents = (xfs_bmbt_rec_t *)
+                        kmem_alloc(XFS_IEXT_BUFSZ, KM_SLEEP);
+        } else if (!ifp->if_real_bytes) {
+                xfs_iext_inline_to_direct(ifp, XFS_IEXT_BUFSZ);
+        } else if (ifp->if_real_bytes < XFS_IEXT_BUFSZ) {
+                xfs_iext_realloc_direct(ifp, XFS_IEXT_BUFSZ);
+        }
+        erp->er_extbuf = ifp->if_u1.if_extents;
+        erp->er_extcount = nextents;
+        erp->er_extoff = 0;
+
+        ifp->if_flags |= XFS_IFEXTIREC;
+        ifp->if_real_bytes = XFS_IEXT_BUFSZ;
+        ifp->if_bytes = nextents * sizeof(xfs_bmbt_rec_t);
+        ifp->if_u1.if_ext_irec = erp;
+
+        return;
+}
+
+/*
+ * Allocate and initialize a new entry in the indirection array.
+ */
+xfs_ext_irec_t *
+xfs_iext_irec_new(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        int             erp_idx)        /* index for new irec */
+{
+        xfs_ext_irec_t  *erp;           /* indirection array pointer */
+        int             i;              /* loop counter */
+        int             nlists;         /* number of irec's (ex lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+
+        /* Resize indirection array */
+        xfs_iext_realloc_indirect(ifp, ++nlists *
+                                  sizeof(xfs_ext_irec_t));
+        /*
+         * Move records down in the array so the
+         * new page can use erp_idx.
+         */
+        erp = ifp->if_u1.if_ext_irec;
+        for (i = nlists - 1; i > erp_idx; i--) {
+                memmove(&erp[i], &erp[i-1], sizeof(xfs_ext_irec_t));
+        }
+        ASSERT(i == erp_idx);
+
+        /* Initialize new extent record */
+        erp = ifp->if_u1.if_ext_irec;
+        erp[erp_idx].er_extbuf = (xfs_bmbt_rec_t *)
+                kmem_alloc(XFS_IEXT_BUFSZ, KM_SLEEP);
+        ifp->if_real_bytes = nlists * XFS_IEXT_BUFSZ;
+        memset(erp[erp_idx].er_extbuf, 0, XFS_IEXT_BUFSZ);
+        erp[erp_idx].er_extcount = 0;
+        erp[erp_idx].er_extoff = erp_idx > 0 ?
+                erp[erp_idx-1].er_extoff + erp[erp_idx-1].er_extcount : 0;
+        return (&erp[erp_idx]);
+}
+
+/*
+ * Remove a record from the indirection array.
+ */
+void
+xfs_iext_irec_remove(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        int             erp_idx)        /* irec index to remove */
+{
+        xfs_ext_irec_t  *erp;           /* indirection array pointer */
+        int             i;              /* loop counter */
+        int             nlists;         /* number of irec's (ex lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        erp = &ifp->if_u1.if_ext_irec[erp_idx];
+        if (erp->er_extbuf) {
+                xfs_iext_irec_update_extoffs(ifp, erp_idx + 1,
+                        -erp->er_extcount);
+                kmem_free(erp->er_extbuf, XFS_IEXT_BUFSZ);
+        }
+        /* Compact extent records */
+        erp = ifp->if_u1.if_ext_irec;
+        for (i = erp_idx; i < nlists - 1; i++) {
+                memmove(&erp[i], &erp[i+1], sizeof(xfs_ext_irec_t));
+        }
+        /*
+         * Manually free the last extent record from the indirection
+         * array.  A call to xfs_iext_realloc_indirect() with a size
+         * of zero would result in a call to xfs_iext_destroy() which
+         * would in turn call this function again, creating a nasty
+         * infinite loop.
+         */
+        if (--nlists) {
+                xfs_iext_realloc_indirect(ifp,
+                        nlists * sizeof(xfs_ext_irec_t));
+        } else {
+                kmem_free(ifp->if_u1.if_ext_irec,
+                        sizeof(xfs_ext_irec_t));
+        }
+        ifp->if_real_bytes = nlists * XFS_IEXT_BUFSZ;
+}
+
+/*
+ * This is called to clean up large amounts of unused memory allocated
+ * by the indirection array.  Before compacting anything though, verify
+ * that the indirection array is still needed and switch back to the
+ * linear extent list (or even the inline buffer) if possible.  The
+ * compaction policy is as follows:
+ *
+ *    Full Compaction: Extents fit into a single page (or inline buffer)
+ *    Full Compaction: Extents occupy less than 10% of allocated space
+ * Partial Compaction: Extents occupy > 10% and < 50% of allocated space
+ *      No Compaction: Extents occupy at least 50% of allocated space
+ */
+void
+xfs_iext_irec_compact(
+        xfs_ifork_t     *ifp)           /* inode fork pointer */
+{
+        xfs_extnum_t    nextents;       /* number of extents in file */
+        int             nlists;         /* number of irec's (ex lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        nextents = ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t);
+
+        if (nextents == 0) {
+                xfs_iext_destroy(ifp);
+        } else if (nextents <= XFS_INLINE_EXTS) {
+                xfs_iext_indirect_to_direct(ifp);
+                xfs_iext_direct_to_inline(ifp, nextents);
+        } else if (nextents <= XFS_LINEAR_EXTS) {
+                xfs_iext_indirect_to_direct(ifp);
+        } else if (nextents < (nlists * XFS_LINEAR_EXTS) >> 3) {
+                xfs_iext_irec_compact_full(ifp);
+        } else if (nextents < (nlists * XFS_LINEAR_EXTS) >> 1) {
+                xfs_iext_irec_compact_pages(ifp);
+        }
+}
+
+/*
+ * Combine extents from neighboring extent pages.
+ */
+void
+xfs_iext_irec_compact_pages(
+        xfs_ifork_t     *ifp)           /* inode fork pointer */
+{
+        xfs_ext_irec_t  *erp, *erp_next;/* pointers to irec entries */
+        int             erp_idx = 0;    /* indirection array index */
+        int             nlists;         /* number of irec's (ex lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        while (erp_idx < nlists - 1) {
+                erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                erp_next = erp + 1;
+                if (erp_next->er_extcount <=
+                    (XFS_LINEAR_EXTS - erp->er_extcount)) {
+                        memmove(&erp->er_extbuf[erp->er_extcount],
+                                erp_next->er_extbuf, erp_next->er_extcount *
+                                sizeof(xfs_bmbt_rec_t));
+                        erp->er_extcount += erp_next->er_extcount;
+                        /*
+                         * Free page before removing extent record
+                         * so er_extoffs don't get modified in
+                         * xfs_iext_irec_remove.
+                         */
+                        kmem_free(erp_next->er_extbuf, XFS_IEXT_BUFSZ);
+                        erp_next->er_extbuf = NULL;
+                        xfs_iext_irec_remove(ifp, erp_idx + 1);
+                        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+                } else {
+                        erp_idx++;
+                }
+        }
+}
+
+/*
+ * Fully compact the extent records managed by the indirection array.
+ */
+void
+xfs_iext_irec_compact_full(
+        xfs_ifork_t     *ifp)                   /* inode fork pointer */
+{
+        xfs_bmbt_rec_t  *ep, *ep_next;          /* extent record pointers */
+        xfs_ext_irec_t  *erp, *erp_next;        /* extent irec pointers */
+        int             erp_idx = 0;            /* extent irec index */
+        int             ext_avail;              /* empty entries in ex list */
+        int             ext_diff;               /* number of exts to add */
+        int             nlists;                 /* number of irec's (ex lists) */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        erp = ifp->if_u1.if_ext_irec;
+        ep = &erp->er_extbuf[erp->er_extcount];
+        erp_next = erp + 1;
+        ep_next = erp_next->er_extbuf;
+        while (erp_idx < nlists - 1) {
+                ext_avail = XFS_LINEAR_EXTS - erp->er_extcount;
+                ext_diff = MIN(ext_avail, erp_next->er_extcount);
+                memcpy(ep, ep_next, ext_diff * sizeof(xfs_bmbt_rec_t));
+                erp->er_extcount += ext_diff;
+                erp_next->er_extcount -= ext_diff;
+                /* Remove next page */
+                if (erp_next->er_extcount == 0) {
+                        /*
+                         * Free page before removing extent record
+                         * so er_extoffs don't get modified in
+                         * xfs_iext_irec_remove.
+                         */
+                        kmem_free(erp_next->er_extbuf,
+                                erp_next->er_extcount * sizeof(xfs_bmbt_rec_t));
+                        erp_next->er_extbuf = NULL;
+                        xfs_iext_irec_remove(ifp, erp_idx + 1);
+                        erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+                /* Update next page */
+                } else {
+                        /* Move rest of page up to become next new page */
+                        memmove(erp_next->er_extbuf, ep_next,
+                                erp_next->er_extcount * sizeof(xfs_bmbt_rec_t));
+                        ep_next = erp_next->er_extbuf;
+                        memset(&ep_next[erp_next->er_extcount], 0,
+                                (XFS_LINEAR_EXTS - erp_next->er_extcount) *
+                                sizeof(xfs_bmbt_rec_t));
+                }
+                if (erp->er_extcount == XFS_LINEAR_EXTS) {
+                        erp_idx++;
+                        if (erp_idx < nlists)
+                                erp = &ifp->if_u1.if_ext_irec[erp_idx];
+                        else
+                                break;
+                }
+                ep = &erp->er_extbuf[erp->er_extcount];
+                erp_next = erp + 1;
+                ep_next = erp_next->er_extbuf;
+        }
+}
+
+/*
+ * This is called to update the er_extoff field in the indirection
+ * array when extents have been added or removed from one of the
+ * extent lists. erp_idx contains the irec index to begin updating
+ * at and ext_diff contains the number of extents that were added
+ * or removed.
+ */
+void
+xfs_iext_irec_update_extoffs(
+        xfs_ifork_t     *ifp,           /* inode fork pointer */
+        int             erp_idx,        /* irec index to update */
+        int             ext_diff)       /* number of new extents */
+{
+        int             i;              /* loop counter */
+        int             nlists;         /* number of irec's (ex lists */
+
+        ASSERT(ifp->if_flags & XFS_IFEXTIREC);
+        nlists = ifp->if_real_bytes / XFS_IEXT_BUFSZ;
+        for (i = erp_idx; i < nlists; i++) {
+                ifp->if_u1.if_ext_irec[i].er_extoff += ext_diff;
+        }
+}