GFS2: Reduce file fragmentation

This patch reduces GFS2 file fragmentation by pre-reserving blocks. The
resulting improved on disk layout greatly speeds up operations in cases
which would have resulted in interlaced allocation of blocks previously.
A typical example of this is 10 parallel dd processes, each writing to a
file in a common dirctory.

The implementation uses an rbtree of reservations attached to each
resource group (and each inode).

Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 523 insertions, 55 deletions

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index fb7079263ea7..4d34887a601d 100644
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -35,6 +35,9 @@
 #define BFITNOENT ((u32)~0)
 #define NO_BLOCK ((u64)~0)
 
+#define RSRV_CONTENTION_FACTOR 4
+#define RGRP_RSRV_MAX_CONTENDERS 2
+
 #if BITS_PER_LONG == 32
 #define LBITMASK   (0x55555555UL)
 #define LBITSKIP55 (0x55555555UL)
@@ -178,6 +181,57 @@ static inline u64 gfs2_bit_search(const __le64 *ptr, u64 mask, u8 state)
 }
 
 /**
+ * rs_cmp - multi-block reservation range compare
+ * @blk: absolute file system block number of the new reservation
+ * @len: number of blocks in the new reservation
+ * @rs: existing reservation to compare against
+ *
+ * returns: 1 if the block range is beyond the reach of the reservation
+ *         -1 if the block range is before the start of the reservation
+ *          0 if the block range overlaps with the reservation
+ */
+static inline int rs_cmp(u64 blk, u32 len, struct gfs2_blkreserv *rs)
+{
+        u64 startblk = gfs2_rs_startblk(rs);
+
+        if (blk >= startblk + rs->rs_free)
+                return 1;
+        if (blk + len - 1 < startblk)
+                return -1;
+        return 0;
+}
+
+/**
+ * rs_find - Find a rgrp multi-block reservation that contains a given block
+ * @rgd: The rgrp
+ * @rgblk: The block we're looking for, relative to the rgrp
+ */
+static struct gfs2_blkreserv *rs_find(struct gfs2_rgrpd *rgd, u32 rgblk)
+{
+        struct rb_node **newn;
+        int rc;
+        u64 fsblk = rgblk + rgd->rd_data0;
+
+        spin_lock(&rgd->rd_rsspin);
+        newn = &rgd->rd_rstree.rb_node;
+        while (*newn) {
+                struct gfs2_blkreserv *cur =
+                        rb_entry(*newn, struct gfs2_blkreserv, rs_node);
+                rc = rs_cmp(fsblk, 1, cur);
+                if (rc < 0)
+                        newn = &((*newn)->rb_left);
+                else if (rc > 0)
+                        newn = &((*newn)->rb_right);
+                else {
+                        spin_unlock(&rgd->rd_rsspin);
+                        return cur;
+                }
+        }
+        spin_unlock(&rgd->rd_rsspin);
+        return NULL;
+}
+
+/**
  * gfs2_bitfit - Search an rgrp's bitmap buffer to find a bit-pair representing
  *       a block in a given allocation state.
  * @buf: the buffer that holds the bitmaps
@@ -424,19 +478,93 @@ void gfs2_free_clones(struct gfs2_rgrpd *rgd)
 int gfs2_rs_alloc(struct gfs2_inode *ip)
 {
         int error = 0;
+        struct gfs2_blkreserv *res;
+
+        if (ip->i_res)
+                return 0;
+
+        res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
+        if (!res)
+                error = -ENOMEM;
 
         down_write(&ip->i_rw_mutex);
-        if (!ip->i_res) {
-                ip->i_res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
-                if (!ip->i_res)
-                        error = -ENOMEM;
-        }
+        if (ip->i_res)
+                kmem_cache_free(gfs2_rsrv_cachep, res);
+        else
+                ip->i_res = res;
         up_write(&ip->i_rw_mutex);
         return error;
 }
 
+static void dump_rs(struct seq_file *seq, struct gfs2_blkreserv *rs)
+{
+        gfs2_print_dbg(seq, "  r: %llu s:%llu b:%u f:%u\n",
+                       rs->rs_rgd->rd_addr, gfs2_rs_startblk(rs), rs->rs_biblk,
+                       rs->rs_free);
+}
+
 /**
- * gfs2_rs_delete - delete a reservation
+ * __rs_deltree - remove a multi-block reservation from the rgd tree
+ * @rs: The reservation to remove
+ *
+ */
+static void __rs_deltree(struct gfs2_blkreserv *rs)
+{
+        struct gfs2_rgrpd *rgd;
+
+        if (!gfs2_rs_active(rs))
+                return;
+
+        rgd = rs->rs_rgd;
+        /* We can't do this: The reason is that when the rgrp is invalidated,
+           it's in the "middle" of acquiring the glock, but the HOLDER bit
+           isn't set yet:
+           BUG_ON(!gfs2_glock_is_locked_by_me(rs->rs_rgd->rd_gl));*/
+        trace_gfs2_rs(NULL, rs, TRACE_RS_TREEDEL);
+
+        if (!RB_EMPTY_ROOT(&rgd->rd_rstree))
+                rb_erase(&rs->rs_node, &rgd->rd_rstree);
+        BUG_ON(!rgd->rd_rs_cnt);
+        rgd->rd_rs_cnt--;
+
+        if (rs->rs_free) {
+                /* return reserved blocks to the rgrp and the ip */
+                BUG_ON(rs->rs_rgd->rd_reserved < rs->rs_free);
+                rs->rs_rgd->rd_reserved -= rs->rs_free;
+                rs->rs_free = 0;
+                clear_bit(GBF_FULL, &rs->rs_bi->bi_flags);
+                smp_mb__after_clear_bit();
+        }
+        /* We can't change any of the step 1 or step 2 components of the rs.
+           E.g. We can't set rs_rgd to NULL because the rgd glock is held and
+           dequeued through this pointer.
+           Can't: atomic_set(&rs->rs_sizehint, 0);
+           Can't: rs->rs_requested = 0;
+           Can't: rs->rs_rgd = NULL;*/
+        rs->rs_bi = NULL;
+        rs->rs_biblk = 0;
+}
+
+/**
+ * gfs2_rs_deltree - remove a multi-block reservation from the rgd tree
+ * @rs: The reservation to remove
+ *
+ */
+void gfs2_rs_deltree(struct gfs2_blkreserv *rs)
+{
+        struct gfs2_rgrpd *rgd;
+
+        if (!gfs2_rs_active(rs))
+                return;
+
+        rgd = rs->rs_rgd;
+        spin_lock(&rgd->rd_rsspin);
+        __rs_deltree(rs);
+        spin_unlock(&rgd->rd_rsspin);
+}
+
+/**
+ * gfs2_rs_delete - delete a multi-block reservation
  * @ip: The inode for this reservation
  *
  */
@@ -444,12 +572,36 @@ void gfs2_rs_delete(struct gfs2_inode *ip)
 {
         down_write(&ip->i_rw_mutex);
         if (ip->i_res) {
+                gfs2_rs_deltree(ip->i_res);
+                trace_gfs2_rs(ip, ip->i_res, TRACE_RS_DELETE);
+                BUG_ON(ip->i_res->rs_free);
                 kmem_cache_free(gfs2_rsrv_cachep, ip->i_res);
                 ip->i_res = NULL;
         }
         up_write(&ip->i_rw_mutex);
 }
 
+/**
+ * return_all_reservations - return all reserved blocks back to the rgrp.
+ * @rgd: the rgrp that needs its space back
+ *
+ * We previously reserved a bunch of blocks for allocation. Now we need to
+ * give them back. This leave the reservation structures in tact, but removes
+ * all of their corresponding "no-fly zones".
+ */
+static void return_all_reservations(struct gfs2_rgrpd *rgd)
+{
+        struct rb_node *n;
+        struct gfs2_blkreserv *rs;
+
+        spin_lock(&rgd->rd_rsspin);
+        while ((n = rb_first(&rgd->rd_rstree))) {
+                rs = rb_entry(n, struct gfs2_blkreserv, rs_node);
+                __rs_deltree(rs);
+        }
+        spin_unlock(&rgd->rd_rsspin);
+}
+
 void gfs2_clear_rgrpd(struct gfs2_sbd *sdp)
 {
         struct rb_node *n;
@@ -472,6 +624,7 @@ void gfs2_clear_rgrpd(struct gfs2_sbd *sdp)
 
                 gfs2_free_clones(rgd);
                 kfree(rgd->rd_bits);
+                return_all_reservations(rgd);
                 kmem_cache_free(gfs2_rgrpd_cachep, rgd);
         }
 }
@@ -649,6 +802,7 @@ static int read_rindex_entry(struct gfs2_inode *ip)
         rgd->rd_data0 = be64_to_cpu(buf.ri_data0);
         rgd->rd_data = be32_to_cpu(buf.ri_data);
         rgd->rd_bitbytes = be32_to_cpu(buf.ri_bitbytes);
+        spin_lock_init(&rgd->rd_rsspin);
 
         error = compute_bitstructs(rgd);
         if (error)
@@ -1115,29 +1269,212 @@ out:
 }
 
 /**
+ * rs_insert - insert a new multi-block reservation into the rgrp's rb_tree
+ * @bi: the bitmap with the blocks
+ * @ip: the inode structure
+ * @biblk: the 32-bit block number relative to the start of the bitmap
+ * @amount: the number of blocks to reserve
+ *
+ * Returns: NULL - reservation was already taken, so not inserted
+ *          pointer to the inserted reservation
+ */
+static struct gfs2_blkreserv *rs_insert(struct gfs2_bitmap *bi,
+                                       struct gfs2_inode *ip, u32 biblk,
+                                       int amount)
+{
+        struct rb_node **newn, *parent = NULL;
+        int rc;
+        struct gfs2_blkreserv *rs = ip->i_res;
+        struct gfs2_rgrpd *rgd = rs->rs_rgd;
+        u64 fsblock = gfs2_bi2rgd_blk(bi, biblk) + rgd->rd_data0;
+
+        spin_lock(&rgd->rd_rsspin);
+        newn = &rgd->rd_rstree.rb_node;
+        BUG_ON(!ip->i_res);
+        BUG_ON(gfs2_rs_active(rs));
+        /* Figure out where to put new node */
+        /*BUG_ON(!gfs2_glock_is_locked_by_me(rgd->rd_gl));*/
+        while (*newn) {
+                struct gfs2_blkreserv *cur =
+                        rb_entry(*newn, struct gfs2_blkreserv, rs_node);
+
+                parent = *newn;
+                rc = rs_cmp(fsblock, amount, cur);
+                if (rc > 0)
+                        newn = &((*newn)->rb_right);
+                else if (rc < 0)
+                        newn = &((*newn)->rb_left);
+                else {
+                        spin_unlock(&rgd->rd_rsspin);
+                        return NULL; /* reservation already in use */
+                }
+        }
+
+        /* Do our reservation work */
+        rs = ip->i_res;
+        rs->rs_free = amount;
+        rs->rs_biblk = biblk;
+        rs->rs_bi = bi;
+        rb_link_node(&rs->rs_node, parent, newn);
+        rb_insert_color(&rs->rs_node, &rgd->rd_rstree);
+
+        /* Do our inode accounting for the reservation */
+        /*BUG_ON(!gfs2_glock_is_locked_by_me(ip->i_gl));*/
+
+        /* Do our rgrp accounting for the reservation */
+        rgd->rd_reserved += amount; /* blocks reserved */
+        rgd->rd_rs_cnt++; /* number of in-tree reservations */
+        spin_unlock(&rgd->rd_rsspin);
+        trace_gfs2_rs(ip, rs, TRACE_RS_INSERT);
+        return rs;
+}
+
+/**
+ * unclaimed_blocks - return number of blocks that aren't spoken for
+ */
+static u32 unclaimed_blocks(struct gfs2_rgrpd *rgd)
+{
+        return rgd->rd_free_clone - rgd->rd_reserved;
+}
+
+/**
+ * rg_mblk_search - find a group of multiple free blocks
+ * @rgd: the resource group descriptor
+ * @rs: the block reservation
+ * @ip: pointer to the inode for which we're reserving blocks
+ *
+ * This is very similar to rgblk_search, except we're looking for whole
+ * 64-bit words that represent a chunk of 32 free blocks. I'm only focusing
+ * on aligned dwords for speed's sake.
+ *
+ * Returns: 0 if successful or BFITNOENT if there isn't enough free space
+ */
+
+static int rg_mblk_search(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip)
+{
+        struct gfs2_bitmap *bi = rgd->rd_bits;
+        const u32 length = rgd->rd_length;
+        u32 blk;
+        unsigned int buf, x, search_bytes;
+        u8 *buffer = NULL;
+        u8 *ptr, *end, *nonzero;
+        u32 goal, rsv_bytes;
+        struct gfs2_blkreserv *rs;
+        u32 best_rs_bytes, unclaimed;
+        int best_rs_blocks;
+
+        /* Find bitmap block that contains bits for goal block */
+        if (rgrp_contains_block(rgd, ip->i_goal))
+                goal = ip->i_goal - rgd->rd_data0;
+        else
+                goal = rgd->rd_last_alloc;
+        for (buf = 0; buf < length; buf++) {
+                bi = rgd->rd_bits + buf;
+                /* Convert scope of "goal" from rgrp-wide to within
+                   found bit block */
+                if (goal < (bi->bi_start + bi->bi_len) * GFS2_NBBY) {
+                        goal -= bi->bi_start * GFS2_NBBY;
+                        goto do_search;
+                }
+        }
+        buf = 0;
+        goal = 0;
+
+do_search:
+        best_rs_blocks = max_t(int, atomic_read(&ip->i_res->rs_sizehint),
+                               (RGRP_RSRV_MINBLKS * rgd->rd_length));
+        best_rs_bytes = (best_rs_blocks *
+                         (1 + (RSRV_CONTENTION_FACTOR * rgd->rd_rs_cnt))) /
+                GFS2_NBBY; /* 1 + is for our not-yet-created reservation */
+        best_rs_bytes = ALIGN(best_rs_bytes, sizeof(u64));
+        unclaimed = unclaimed_blocks(rgd);
+        if (best_rs_bytes * GFS2_NBBY > unclaimed)
+                best_rs_bytes = unclaimed >> GFS2_BIT_SIZE;
+
+        for (x = 0; x <= length; x++) {
+                bi = rgd->rd_bits + buf;
+
+                if (test_bit(GBF_FULL, &bi->bi_flags))
+                        goto skip;
+
+                WARN_ON(!buffer_uptodate(bi->bi_bh));
+                if (bi->bi_clone)
+                        buffer = bi->bi_clone + bi->bi_offset;
+                else
+                        buffer = bi->bi_bh->b_data + bi->bi_offset;
+
+                /* We have to keep the reservations aligned on u64 boundaries
+                   otherwise we could get situations where a byte can't be
+                   used because it's after a reservation, but a free bit still
+                   is within the reservation's area. */
+                ptr = buffer + ALIGN(goal >> GFS2_BIT_SIZE, sizeof(u64));
+                end = (buffer + bi->bi_len);
+                while (ptr < end) {
+                        rsv_bytes = 0;
+                        if ((ptr + best_rs_bytes) <= end)
+                                search_bytes = best_rs_bytes;
+                        else
+                                search_bytes = end - ptr;
+                        BUG_ON(!search_bytes);
+                        nonzero = memchr_inv(ptr, 0, search_bytes);
+                        /* If the lot is all zeroes, reserve the whole size. If
+                           there's enough zeroes to satisfy the request, use
+                           what we can. If there's not enough, keep looking. */
+                        if (nonzero == NULL)
+                                rsv_bytes = search_bytes;
+                        else if ((nonzero - ptr) * GFS2_NBBY >=
+                                 ip->i_res->rs_requested)
+                                rsv_bytes = (nonzero - ptr);
+
+                        if (rsv_bytes) {
+                                blk = ((ptr - buffer) * GFS2_NBBY);
+                                BUG_ON(blk >= bi->bi_len * GFS2_NBBY);
+                                rs = rs_insert(bi, ip, blk,
+                                               rsv_bytes * GFS2_NBBY);
+                                if (IS_ERR(rs))
+                                        return PTR_ERR(rs);
+                                if (rs)
+                                        return 0;
+                        }
+                        ptr += ALIGN(search_bytes, sizeof(u64));
+                }
+skip:
+                /* Try next bitmap block (wrap back to rgrp header
+                   if at end) */
+                buf++;
+                buf %= length;
+                goal = 0;
+        }
+
+        return BFITNOENT;
+}
+
+/**
  * try_rgrp_fit - See if a given reservation will fit in a given RG
  * @rgd: the RG data
  * @ip: the inode
  *
  * If there's room for the requested blocks to be allocated from the RG:
+ * This will try to get a multi-block reservation first, and if that doesn't
+ * fit, it will take what it can.
  *
  * Returns: 1 on success (it fits), 0 on failure (it doesn't fit)
  */
 
-static int try_rgrp_fit(const struct gfs2_rgrpd *rgd, const struct gfs2_inode *ip)
+static int try_rgrp_fit(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip)
 {
-        const struct gfs2_blkreserv *rs = ip->i_res;
+        struct gfs2_blkreserv *rs = ip->i_res;
 
         if (rgd->rd_flags & (GFS2_RGF_NOALLOC | GFS2_RDF_ERROR))
                 return 0;
-        if (rgd->rd_free_clone >= rs->rs_requested)
+        /* Look for a multi-block reservation. */
+        if (unclaimed_blocks(rgd) >= RGRP_RSRV_MINBLKS &&
+            rg_mblk_search(rgd, ip) != BFITNOENT)
+                return 1;
+        if (unclaimed_blocks(rgd) >= rs->rs_requested)
                 return 1;
-        return 0;
-}
 
-static inline u32 gfs2_bi2rgd_blk(struct gfs2_bitmap *bi, u32 blk)
-{
-        return (bi->bi_start * GFS2_NBBY) + blk;
+        return 0;
 }
 
 /**
@@ -1217,7 +1554,7 @@ static void try_rgrp_unlink(struct gfs2_rgrpd *rgd, u64 *last_unlinked, u64 skip
 int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested)
 {
         struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
-        struct gfs2_rgrpd *rgd, *begin = NULL;
+        struct gfs2_rgrpd *begin = NULL;
         struct gfs2_blkreserv *rs = ip->i_res;
         int error = 0, rg_locked, flags = LM_FLAG_TRY;
         u64 last_unlinked = NO_BLOCK;
@@ -1225,32 +1562,40 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested)
 
         if (sdp->sd_args.ar_rgrplvb)
                 flags |= GL_SKIP;
-        rs = ip->i_res;
         rs->rs_requested = requested;
         if (gfs2_assert_warn(sdp, requested)) {
                 error = -EINVAL;
                 goto out;
         }
-
-        if (ip->i_rgd && rgrp_contains_block(ip->i_rgd, ip->i_goal))
-                rgd = begin = ip->i_rgd;
-        else
-                rgd = begin = gfs2_blk2rgrpd(sdp, ip->i_goal, 1);
-
-        if (rgd == NULL)
+        if (gfs2_rs_active(rs)) {
+                begin = rs->rs_rgd;
+                flags = 0; /* Yoda: Do or do not. There is no try */
+        } else if (ip->i_rgd && rgrp_contains_block(ip->i_rgd, ip->i_goal)) {
+                rs->rs_rgd = begin = ip->i_rgd;
+        } else {
+                rs->rs_rgd = begin = gfs2_blk2rgrpd(sdp, ip->i_goal, 1);
+        }
+        if (rs->rs_rgd == NULL)
                 return -EBADSLT;
 
         while (loops < 3) {
                 rg_locked = 0;
 
-                if (gfs2_glock_is_locked_by_me(rgd->rd_gl)) {
+                if (gfs2_glock_is_locked_by_me(rs->rs_rgd->rd_gl)) {
                         rg_locked = 1;
                         error = 0;
+                } else if (!loops && !gfs2_rs_active(rs) &&
+                           rs->rs_rgd->rd_rs_cnt > RGRP_RSRV_MAX_CONTENDERS) {
+                        /* If the rgrp already is maxed out for contenders,
+                           we can eliminate it as a "first pass" without even
+                           requesting the rgrp glock. */
+                        error = GLR_TRYFAILED;
                 } else {
-                        error = gfs2_glock_nq_init(rgd->rd_gl, LM_ST_EXCLUSIVE,
-                                                   flags, &rs->rs_rgd_gh);
+                        error = gfs2_glock_nq_init(rs->rs_rgd->rd_gl,
+                                                   LM_ST_EXCLUSIVE, flags,
+                                                   &rs->rs_rgd_gh);
                         if (!error && sdp->sd_args.ar_rgrplvb) {
-                                error = update_rgrp_lvb(rgd);
+                                error = update_rgrp_lvb(rs->rs_rgd);
                                 if (error) {
                                         gfs2_glock_dq_uninit(&rs->rs_rgd_gh);
                                         return error;
@@ -1259,25 +1604,37 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested)
                 }
                 switch (error) {
                 case 0:
-                        if (try_rgrp_fit(rgd, ip)) {
+                        if (gfs2_rs_active(rs)) {
+                                if (unclaimed_blocks(rs->rs_rgd) +
+                                    rs->rs_free >= rs->rs_requested) {
+                                        ip->i_rgd = rs->rs_rgd;
+                                        return 0;
+                                }
+                                /* We have a multi-block reservation, but the
+                                   rgrp doesn't have enough free blocks to
+                                   satisfy the request. Free the reservation
+                                   and look for a suitable rgrp. */
+                                gfs2_rs_deltree(rs);
+                        }
+                        if (try_rgrp_fit(rs->rs_rgd, ip)) {
                                 if (sdp->sd_args.ar_rgrplvb)
-                                        gfs2_rgrp_bh_get(rgd);
-                                ip->i_rgd = rgd;
+                                        gfs2_rgrp_bh_get(rs->rs_rgd);
+                                ip->i_rgd = rs->rs_rgd;
                                 return 0;
                         }
-                        if (rgd->rd_flags & GFS2_RDF_CHECK) {
+                        if (rs->rs_rgd->rd_flags & GFS2_RDF_CHECK) {
                                 if (sdp->sd_args.ar_rgrplvb)
-                                        gfs2_rgrp_bh_get(rgd);
-                                try_rgrp_unlink(rgd, &last_unlinked,
+                                        gfs2_rgrp_bh_get(rs->rs_rgd);
+                                try_rgrp_unlink(rs->rs_rgd, &last_unlinked,
                                                 ip->i_no_addr);
                         }
                         if (!rg_locked)
                                 gfs2_glock_dq_uninit(&rs->rs_rgd_gh);
                         /* fall through */
                 case GLR_TRYFAILED:
-                        rgd = gfs2_rgrpd_get_next(rgd);
-                        rgd = rgd ? : begin; /* if NULL, wrap */
-                        if (rgd != begin) /* If we didn't wrap */
+                        rs->rs_rgd = gfs2_rgrpd_get_next(rs->rs_rgd);
+                        rs->rs_rgd = rs->rs_rgd ? : begin; /* if NULL, wrap */
+                        if (rs->rs_rgd != begin) /* If we didn't wrap */
                                 break;
 
                         flags &= ~LM_FLAG_TRY;
@@ -1315,6 +1672,12 @@ void gfs2_inplace_release(struct gfs2_inode *ip)
 {
         struct gfs2_blkreserv *rs = ip->i_res;
 
+        if (!rs)
+                return;
+
+        if (!rs->rs_free)
+                gfs2_rs_deltree(rs);
+
         if (rs->rs_rgd_gh.gh_gl)
                 gfs2_glock_dq_uninit(&rs->rs_rgd_gh);
         rs->rs_requested = 0;
@@ -1413,7 +1776,27 @@ do_search:
                 if (state != GFS2_BLKST_UNLINKED && bi->bi_clone)
                         buffer = bi->bi_clone + bi->bi_offset;
 
-                biblk = gfs2_bitfit(buffer, bi->bi_len, goal, state);
+                while (1) {
+                        struct gfs2_blkreserv *rs;
+                        u32 rgblk;
+
+                        biblk = gfs2_bitfit(buffer, bi->bi_len, goal, state);
+                        if (biblk == BFITNOENT)
+                                break;
+                        /* Check if this block is reserved() */
+                        rgblk = gfs2_bi2rgd_blk(bi, biblk);
+                        rs = rs_find(rgd, rgblk);
+                        if (rs == NULL)
+                                break;
+
+                        BUG_ON(rs->rs_bi != bi);
+                        biblk = BFITNOENT;
+                        /* This should jump to the first block after the
+                           reservation. */
+                        goal = rs->rs_biblk + rs->rs_free;
+                        if (goal >= bi->bi_len * GFS2_NBBY)
+                                break;
+                }
                 if (biblk != BFITNOENT)
                         break;
 
@@ -1449,8 +1832,9 @@ static u64 gfs2_alloc_extent(struct gfs2_rgrpd *rgd, struct gfs2_bitmap *bi,
                              u32 blk, bool dinode, unsigned int *n)
 {
         const unsigned int elen = *n;
-        u32 goal;
+        u32 goal, rgblk;
         const u8 *buffer = NULL;
+        struct gfs2_blkreserv *rs;
 
         *n = 0;
         buffer = bi->bi_bh->b_data + bi->bi_offset;
@@ -1463,6 +1847,10 @@ static u64 gfs2_alloc_extent(struct gfs2_rgrpd *rgd, struct gfs2_bitmap *bi,
                 goal++;
                 if (goal >= (bi->bi_len * GFS2_NBBY))
                         break;
+                rgblk = gfs2_bi2rgd_blk(bi, goal);
+                rs = rs_find(rgd, rgblk);
+                if (rs) /* Oops, we bumped into someone's reservation */
+                        break;
                 if (gfs2_testbit(rgd, buffer, bi->bi_len, goal) !=
                     GFS2_BLKST_FREE)
                         break;
@@ -1538,12 +1926,22 @@ static struct gfs2_rgrpd *rgblk_free(struct gfs2_sbd *sdp, u64 bstart,
 
 int gfs2_rgrp_dump(struct seq_file *seq, const struct gfs2_glock *gl)
 {
-        const struct gfs2_rgrpd *rgd = gl->gl_object;
+        struct gfs2_rgrpd *rgd = gl->gl_object;
+        struct gfs2_blkreserv *trs;
+        const struct rb_node *n;
+
         if (rgd == NULL)
                 return 0;
-        gfs2_print_dbg(seq, " R: n:%llu f:%02x b:%u/%u i:%u\n",
+        gfs2_print_dbg(seq, " R: n:%llu f:%02x b:%u/%u i:%u r:%u\n",
                        (unsigned long long)rgd->rd_addr, rgd->rd_flags,
-                       rgd->rd_free, rgd->rd_free_clone, rgd->rd_dinodes);
+                       rgd->rd_free, rgd->rd_free_clone, rgd->rd_dinodes,
+                       rgd->rd_reserved);
+        spin_lock(&rgd->rd_rsspin);
+        for (n = rb_first(&rgd->rd_rstree); n; n = rb_next(&trs->rs_node)) {
+                trs = rb_entry(n, struct gfs2_blkreserv, rs_node);
+                dump_rs(seq, trs);
+        }
+        spin_unlock(&rgd->rd_rsspin);
         return 0;
 }
 
@@ -1558,10 +1956,63 @@ static void gfs2_rgrp_error(struct gfs2_rgrpd *rgd)
 }
 
 /**
+ * claim_reserved_blks - Claim previously reserved blocks
+ * @ip: the inode that's claiming the reservation
+ * @dinode: 1 if this block is a dinode block, otherwise data block
+ * @nblocks: desired extent length
+ *
+ * Lay claim to previously allocated block reservation blocks.
+ * Returns: Starting block number of the blocks claimed.
+ * Sets *nblocks to the actual extent length allocated.
+ */
+static u64 claim_reserved_blks(struct gfs2_inode *ip, bool dinode,
+                               unsigned int *nblocks)
+{
+        struct gfs2_blkreserv *rs = ip->i_res;
+        struct gfs2_rgrpd *rgd = rs->rs_rgd;
+        struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
+        struct gfs2_bitmap *bi;
+        u64 start_block = gfs2_rs_startblk(rs);
+        const unsigned int elen = *nblocks;
+
+        /*BUG_ON(!gfs2_glock_is_locked_by_me(ip->i_gl));*/
+        gfs2_assert_withdraw(sdp, rgd);
+        /*BUG_ON(!gfs2_glock_is_locked_by_me(rgd->rd_gl));*/
+        bi = rs->rs_bi;
+        gfs2_trans_add_bh(rgd->rd_gl, bi->bi_bh, 1);
+
+        for (*nblocks = 0; *nblocks < elen && rs->rs_free; (*nblocks)++) {
+                /* Make sure the bitmap hasn't changed */
+                gfs2_setbit(rgd, bi->bi_clone, bi, rs->rs_biblk,
+                            dinode ? GFS2_BLKST_DINODE : GFS2_BLKST_USED);
+                rs->rs_biblk++;
+                rs->rs_free--;
+
+                BUG_ON(!rgd->rd_reserved);
+                rgd->rd_reserved--;
+                dinode = false;
+                trace_gfs2_rs(ip, rs, TRACE_RS_CLAIM);
+        }
+
+        if (!rs->rs_free) {
+                struct gfs2_rgrpd *rgd = ip->i_res->rs_rgd;
+
+                gfs2_rs_deltree(rs);
+                /* -nblocks because we haven't returned to do the math yet.
+                   I'm doing the math backwards to prevent negative numbers,
+                   but think of it as:
+                   if (unclaimed_blocks(rgd) - *nblocks >= RGRP_RSRV_MINBLKS */
+                if (unclaimed_blocks(rgd) >= RGRP_RSRV_MINBLKS + *nblocks)
+                        rg_mblk_search(rgd, ip);
+        }
+        return start_block;
+}
+
+/**
  * gfs2_alloc_blocks - Allocate one or more blocks of data and/or a dinode
  * @ip: the inode to allocate the block for
  * @bn: Used to return the starting block number
- * @ndata: requested number of blocks/extent length (value/result)
+ * @nblocks: requested number of blocks/extent length (value/result)
  * @dinode: 1 if we're allocating a dinode block, else 0
  * @generation: the generation number of the inode
  *
@@ -1586,20 +2037,34 @@ int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *nblocks,
         if (ip->i_res->rs_requested == 0)
                 return -ECANCELED;
 
-        rgd = ip->i_rgd;
-
-        if (!dinode && rgrp_contains_block(rgd, ip->i_goal))
-                goal = ip->i_goal - rgd->rd_data0;
-        else
-                goal = rgd->rd_last_alloc;
-
-        blk = rgblk_search(rgd, goal, GFS2_BLKST_FREE, &bi);
+        /* Check if we have a multi-block reservation, and if so, claim the
+           next free block from it. */
+        if (gfs2_rs_active(ip->i_res)) {
+                BUG_ON(!ip->i_res->rs_free);
+                rgd = ip->i_res->rs_rgd;
+                block = claim_reserved_blks(ip, dinode, nblocks);
+        } else {
+                rgd = ip->i_rgd;
 
-        /* Since all blocks are reserved in advance, this shouldn't happen */
-        if (blk == BFITNOENT)
-                goto rgrp_error;
+                if (!dinode && rgrp_contains_block(rgd, ip->i_goal))
+                        goal = ip->i_goal - rgd->rd_data0;
+                else
+                        goal = rgd->rd_last_alloc;
+
+                blk = rgblk_search(rgd, goal, GFS2_BLKST_FREE, &bi);
+
+                /* Since all blocks are reserved in advance, this shouldn't
+                   happen */
+                if (blk == BFITNOENT) {
+                        printk(KERN_WARNING "BFITNOENT, nblocks=%u\n",
+                               *nblocks);
+                        printk(KERN_WARNING "FULL=%d\n",
+                               test_bit(GBF_FULL, &rgd->rd_bits->bi_flags));
+                        goto rgrp_error;
+                }
 
-        block = gfs2_alloc_extent(rgd, bi, blk, dinode, nblocks);
+                block = gfs2_alloc_extent(rgd, bi, blk, dinode, nblocks);
+        }
         ndata = *nblocks;
         if (dinode)
                 ndata--;
@@ -1616,8 +2081,10 @@ int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *nblocks,
                         brelse(dibh);
                 }
         }
-        if (rgd->rd_free < *nblocks)
+        if (rgd->rd_free < *nblocks) {
+                printk(KERN_WARNING "nblocks=%u\n", *nblocks);
                 goto rgrp_error;
+        }
 
         rgd->rd_free -= *nblocks;
         if (dinode) {
@@ -1877,6 +2344,7 @@ void gfs2_rlist_free(struct gfs2_rgrp_list *rlist)
                 for (x = 0; x < rlist->rl_rgrps; x++)
                         gfs2_holder_uninit(&rlist->rl_ghs[x]);
                 kfree(rlist->rl_ghs);
+                rlist->rl_ghs = NULL;
         }
 }