pnfsblock: merge extents

Replace a stub, so that extents underlying the layouts are properly
added, merged, or ignored as necessary.

Signed-off-by: Fred Isaman <iisaman@citi.umich.edu>
[pnfsblock: delete the new node before put it]
Signed-off-by: Mingyang Guo <guomingyang@nrchpc.ac.cn>
Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Peng Tao <peng_tao@emc.com>
Signed-off-by: Benny Halevy <bhalevy@tonian.com>
Signed-off-by: Jim Rees <rees@umich.edu>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

2 files changed, 119 insertions, 0 deletions

diff --git a/fs/nfs/blocklayout/blocklayout.h b/fs/nfs/blocklayout/blocklayout.h
index 3e05b08d5347..581d8f47a723 100644
--- a/fs/nfs/blocklayout/blocklayout.h
+++ b/fs/nfs/blocklayout/blocklayout.h
@@ -80,6 +80,14 @@ enum extentclass4 {
         EXTENT_LISTS    = 2,
 };
 
+static inline int bl_choose_list(enum exstate4 state)
+{
+        if (state == PNFS_BLOCK_READ_DATA || state == PNFS_BLOCK_NONE_DATA)
+                return RO_EXTENT;
+        else
+                return RW_EXTENT;
+}
+
 struct pnfs_block_layout {
         struct pnfs_layout_hdr bl_layout;
         struct pnfs_inval_markings bl_inval; /* tracks INVAL->RW transition */
@@ -137,5 +145,10 @@ int nfs4_blk_process_layoutget(struct pnfs_layout_hdr *lo,
 /* blocklayoutdm.c */
 void bl_free_block_dev(struct pnfs_block_dev *bdev);
 
+/* extents.c */
 void bl_put_extent(struct pnfs_block_extent *be);
+struct pnfs_block_extent *bl_alloc_extent(void);
+int bl_add_merge_extent(struct pnfs_block_layout *bl,
+                         struct pnfs_block_extent *new);
+
 #endif /* FS_NFS_NFS4BLOCKLAYOUT_H */
diff --git a/fs/nfs/blocklayout/extents.c b/fs/nfs/blocklayout/extents.c
index d0ca7604d33e..ee4891f32492 100644
--- a/fs/nfs/blocklayout/extents.c
+++ b/fs/nfs/blocklayout/extents.c
@@ -87,3 +87,109 @@ static void print_elist(struct list_head *list)
         }
         dprintk("****************\n");
 }
+
+static inline int
+extents_consistent(struct pnfs_block_extent *old, struct pnfs_block_extent *new)
+{
+        /* Note this assumes new->be_f_offset >= old->be_f_offset */
+        return (new->be_state == old->be_state) &&
+                ((new->be_state == PNFS_BLOCK_NONE_DATA) ||
+                 ((new->be_v_offset - old->be_v_offset ==
+                   new->be_f_offset - old->be_f_offset) &&
+                  new->be_mdev == old->be_mdev));
+}
+
+/* Adds new to appropriate list in bl, modifying new and removing existing
+ * extents as appropriate to deal with overlaps.
+ *
+ * See bl_find_get_extent for list constraints.
+ *
+ * Refcount on new is already set.  If end up not using it, or error out,
+ * need to put the reference.
+ *
+ * bl->bl_ext_lock is held by caller.
+ */
+int
+bl_add_merge_extent(struct pnfs_block_layout *bl,
+                     struct pnfs_block_extent *new)
+{
+        struct pnfs_block_extent *be, *tmp;
+        sector_t end = new->be_f_offset + new->be_length;
+        struct list_head *list;
+
+        dprintk("%s enter with be=%p\n", __func__, new);
+        print_bl_extent(new);
+        list = &bl->bl_extents[bl_choose_list(new->be_state)];
+        print_elist(list);
+
+        /* Scan for proper place to insert, extending new to the left
+         * as much as possible.
+         */
+        list_for_each_entry_safe(be, tmp, list, be_node) {
+                if (new->be_f_offset < be->be_f_offset)
+                        break;
+                if (end <= be->be_f_offset + be->be_length) {
+                        /* new is a subset of existing be*/
+                        if (extents_consistent(be, new)) {
+                                dprintk("%s: new is subset, ignoring\n",
+                                        __func__);
+                                bl_put_extent(new);
+                                return 0;
+                        } else
+                                goto out_err;
+                } else if (new->be_f_offset <=
+                                be->be_f_offset + be->be_length) {
+                        /* new overlaps or abuts existing be */
+                        if (extents_consistent(be, new)) {
+                                /* extend new to fully replace be */
+                                new->be_length += new->be_f_offset -
+                                                  be->be_f_offset;
+                                new->be_f_offset = be->be_f_offset;
+                                new->be_v_offset = be->be_v_offset;
+                                dprintk("%s: removing %p\n", __func__, be);
+                                list_del(&be->be_node);
+                                bl_put_extent(be);
+                        } else if (new->be_f_offset !=
+                                   be->be_f_offset + be->be_length)
+                                goto out_err;
+                }
+        }
+        /* Note that if we never hit the above break, be will not point to a
+         * valid extent.  However, in that case &be->be_node==list.
+         */
+        list_add_tail(&new->be_node, &be->be_node);
+        dprintk("%s: inserting new\n", __func__);
+        print_elist(list);
+        /* Scan forward for overlaps.  If we find any, extend new and
+         * remove the overlapped extent.
+         */
+        be = list_prepare_entry(new, list, be_node);
+        list_for_each_entry_safe_continue(be, tmp, list, be_node) {
+                if (end < be->be_f_offset)
+                        break;
+                /* new overlaps or abuts existing be */
+                if (extents_consistent(be, new)) {
+                        if (end < be->be_f_offset + be->be_length) {
+                                /* extend new to fully cover be */
+                                end = be->be_f_offset + be->be_length;
+                                new->be_length = end - new->be_f_offset;
+                        }
+                        dprintk("%s: removing %p\n", __func__, be);
+                        list_del(&be->be_node);
+                        bl_put_extent(be);
+                } else if (end != be->be_f_offset) {
+                        list_del(&new->be_node);
+                        goto out_err;
+                }
+        }
+        dprintk("%s: after merging\n", __func__);
+        print_elist(list);
+        /* FIXME - The per-list consistency checks have all been done,
+         * should now check cross-list consistency.
+         */
+        return 0;
+
+ out_err:
+        bl_put_extent(new);
+        return -EIO;
+}