Btrfs: Add fallocate support v2

This patch updates btrfs-progs for fallocate support.

fallocate is a little different in Btrfs because we need to tell the
COW system that a given preallocated extent doesn't need to be
cow'd as long as there are no snapshots of it.  This leverages the
-o nodatacow checks.
 
Signed-off-by: Yan Zheng <zheng.yan@oracle.com>

1 files changed, 241 insertions, 4 deletions

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1a0510ad030c..238a8e215eb9 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -381,7 +381,7 @@ int noinline btrfs_drop_extents(struct btrfs_trans_handle *trans,
         int keep;
         int slot;
         int bookend;
-        int found_type;
+        int found_type = 0;
         int found_extent;
         int found_inline;
         int recow;
@@ -442,7 +442,8 @@ next_slot:
                                                                   extent);
                         other_encoding = btrfs_file_extent_other_encoding(leaf,
                                                                   extent);
-                        if (found_type == BTRFS_FILE_EXTENT_REG) {
+                        if (found_type == BTRFS_FILE_EXTENT_REG ||
+                            found_type == BTRFS_FILE_EXTENT_PREALLOC) {
                                 extent_end =
                                      btrfs_file_extent_disk_bytenr(leaf,
                                                                    extent);
@@ -609,8 +610,7 @@ next_slot:
                          */
                         btrfs_set_file_extent_ram_bytes(leaf, extent,
                                                         ram_bytes);
-                        btrfs_set_file_extent_type(leaf, extent,
-                                                   BTRFS_FILE_EXTENT_REG);
+                        btrfs_set_file_extent_type(leaf, extent, found_type);
 
                         btrfs_mark_buffer_dirty(path->nodes[0]);
 
@@ -661,6 +661,243 @@ out:
         return ret;
 }
 
+static int extent_mergeable(struct extent_buffer *leaf, int slot,
+                            u64 objectid, u64 bytenr, u64 *start, u64 *end)
+{
+        struct btrfs_file_extent_item *fi;
+        struct btrfs_key key;
+        u64 extent_end;
+
+        if (slot < 0 || slot >= btrfs_header_nritems(leaf))
+                return 0;
+
+        btrfs_item_key_to_cpu(leaf, &key, slot);
+        if (key.objectid != objectid || key.type != BTRFS_EXTENT_DATA_KEY)
+                return 0;
+
+        fi = btrfs_item_ptr(leaf, slot, struct btrfs_file_extent_item);
+        if (btrfs_file_extent_type(leaf, fi) != BTRFS_FILE_EXTENT_REG ||
+            btrfs_file_extent_disk_bytenr(leaf, fi) != bytenr ||
+            btrfs_file_extent_compression(leaf, fi) ||
+            btrfs_file_extent_encryption(leaf, fi) ||
+            btrfs_file_extent_other_encoding(leaf, fi))
+                return 0;
+
+        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
+        if ((*start && *start != key.offset) || (*end && *end != extent_end))
+                return 0;
+
+        *start = key.offset;
+        *end = extent_end;
+        return 1;
+}
+
+/*
+ * Mark extent in the range start - end as written.
+ *
+ * This changes extent type from 'pre-allocated' to 'regular'. If only
+ * part of extent is marked as written, the extent will be split into
+ * two or three.
+ */
+int btrfs_mark_extent_written(struct btrfs_trans_handle *trans,
+                              struct btrfs_root *root,
+                              struct inode *inode, u64 start, u64 end)
+{
+        struct extent_buffer *leaf;
+        struct btrfs_path *path;
+        struct btrfs_file_extent_item *fi;
+        struct btrfs_key key;
+        u64 bytenr;
+        u64 num_bytes;
+        u64 extent_end;
+        u64 extent_offset;
+        u64 other_start;
+        u64 other_end;
+        u64 split = start;
+        u64 locked_end = end;
+        int extent_type;
+        int split_end = 1;
+        int ret;
+
+        btrfs_drop_extent_cache(inode, start, end - 1, 0);
+
+        path = btrfs_alloc_path();
+        BUG_ON(!path);
+again:
+        key.objectid = inode->i_ino;
+        key.type = BTRFS_EXTENT_DATA_KEY;
+        if (split == start)
+                key.offset = split;
+        else
+                key.offset = split - 1;
+
+        ret = btrfs_search_slot(trans, root, &key, path, -1, 1);
+        if (ret > 0 && path->slots[0] > 0)
+                path->slots[0]--;
+
+        leaf = path->nodes[0];
+        btrfs_item_key_to_cpu(leaf, &key, path->slots[0]);
+        BUG_ON(key.objectid != inode->i_ino ||
+               key.type != BTRFS_EXTENT_DATA_KEY);
+        fi = btrfs_item_ptr(leaf, path->slots[0],
+                            struct btrfs_file_extent_item);
+        extent_type = btrfs_file_extent_type(leaf, fi);
+        BUG_ON(extent_type != BTRFS_FILE_EXTENT_PREALLOC);
+        extent_end = key.offset + btrfs_file_extent_num_bytes(leaf, fi);
+        BUG_ON(key.offset > start || extent_end < end);
+
+        bytenr = btrfs_file_extent_disk_bytenr(leaf, fi);
+        num_bytes = btrfs_file_extent_disk_num_bytes(leaf, fi);
+        extent_offset = btrfs_file_extent_offset(leaf, fi);
+
+        if (key.offset == start)
+                split = end;
+
+        if (key.offset == start && extent_end == end) {
+                int del_nr = 0;
+                int del_slot = 0;
+                u64 leaf_owner = btrfs_header_owner(leaf);
+                u64 leaf_gen = btrfs_header_generation(leaf);
+                other_start = end;
+                other_end = 0;
+                if (extent_mergeable(leaf, path->slots[0] + 1, inode->i_ino,
+                                     bytenr, &other_start, &other_end)) {
+                        extent_end = other_end;
+                        del_slot = path->slots[0] + 1;
+                        del_nr++;
+                        ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
+                                                leaf->start, leaf_owner,
+                                                leaf_gen, inode->i_ino, 0);
+                        BUG_ON(ret);
+                }
+                other_start = 0;
+                other_end = start;
+                if (extent_mergeable(leaf, path->slots[0] - 1, inode->i_ino,
+                                     bytenr, &other_start, &other_end)) {
+                        key.offset = other_start;
+                        del_slot = path->slots[0];
+                        del_nr++;
+                        ret = btrfs_free_extent(trans, root, bytenr, num_bytes,
+                                                leaf->start, leaf_owner,
+                                                leaf_gen, inode->i_ino, 0);
+                        BUG_ON(ret);
+                }
+                split_end = 0;
+                if (del_nr == 0) {
+                        btrfs_set_file_extent_type(leaf, fi,
+                                                   BTRFS_FILE_EXTENT_REG);
+                        goto done;
+                }
+
+                fi = btrfs_item_ptr(leaf, del_slot - 1,
+                                    struct btrfs_file_extent_item);
+                btrfs_set_file_extent_type(leaf, fi, BTRFS_FILE_EXTENT_REG);
+                btrfs_set_file_extent_num_bytes(leaf, fi,
+                                                extent_end - key.offset);
+                btrfs_mark_buffer_dirty(leaf);
+
+                ret = btrfs_del_items(trans, root, path, del_slot, del_nr);
+                BUG_ON(ret);
+                goto done;
+        } else if (split == start) {
+                if (locked_end < extent_end) {
+                        ret = try_lock_extent(&BTRFS_I(inode)->io_tree,
+                                        locked_end, extent_end - 1, GFP_NOFS);
+                        if (!ret) {
+                                btrfs_release_path(root, path);
+                                lock_extent(&BTRFS_I(inode)->io_tree,
+                                        locked_end, extent_end - 1, GFP_NOFS);
+                                locked_end = extent_end;
+                                goto again;
+                        }
+                        locked_end = extent_end;
+                }
+                btrfs_set_file_extent_num_bytes(leaf, fi, split - key.offset);
+                extent_offset += split - key.offset;
+        } else  {
+                BUG_ON(key.offset != start);
+                btrfs_set_file_extent_offset(leaf, fi, extent_offset +
+                                             split - key.offset);
+                btrfs_set_file_extent_num_bytes(leaf, fi, extent_end - split);
+                key.offset = split;
+                btrfs_set_item_key_safe(trans, root, path, &key);
+                extent_end = split;
+        }
+
+        if (extent_end == end) {
+                split_end = 0;
+                extent_type = BTRFS_FILE_EXTENT_REG;
+        }
+        if (extent_end == end && split == start) {
+                other_start = end;
+                other_end = 0;
+                if (extent_mergeable(leaf, path->slots[0] + 1, inode->i_ino,
+                                     bytenr, &other_start, &other_end)) {
+                        path->slots[0]++;
+                        fi = btrfs_item_ptr(leaf, path->slots[0],
+                                            struct btrfs_file_extent_item);
+                        key.offset = split;
+                        btrfs_set_item_key_safe(trans, root, path, &key);
+                        btrfs_set_file_extent_offset(leaf, fi, extent_offset);
+                        btrfs_set_file_extent_num_bytes(leaf, fi,
+                                                        other_end - split);
+                        goto done;
+                }
+        }
+        if (extent_end == end && split == end) {
+                other_start = 0;
+                other_end = start;
+                if (extent_mergeable(leaf, path->slots[0] - 1 , inode->i_ino,
+                                     bytenr, &other_start, &other_end)) {
+                        path->slots[0]--;
+                        fi = btrfs_item_ptr(leaf, path->slots[0],
+                                            struct btrfs_file_extent_item);
+                        btrfs_set_file_extent_num_bytes(leaf, fi, extent_end -
+                                                        other_start);
+                        goto done;
+                }
+        }
+
+        btrfs_mark_buffer_dirty(leaf);
+        btrfs_release_path(root, path);
+
+        key.offset = start;
+        ret = btrfs_insert_empty_item(trans, root, path, &key, sizeof(*fi));
+        BUG_ON(ret);
+
+        leaf = path->nodes[0];
+        fi = btrfs_item_ptr(leaf, path->slots[0],
+                            struct btrfs_file_extent_item);
+        btrfs_set_file_extent_generation(leaf, fi, trans->transid);
+        btrfs_set_file_extent_type(leaf, fi, extent_type);
+        btrfs_set_file_extent_disk_bytenr(leaf, fi, bytenr);
+        btrfs_set_file_extent_disk_num_bytes(leaf, fi, num_bytes);
+        btrfs_set_file_extent_offset(leaf, fi, extent_offset);
+        btrfs_set_file_extent_num_bytes(leaf, fi, extent_end - key.offset);
+        btrfs_set_file_extent_ram_bytes(leaf, fi, num_bytes);
+        btrfs_set_file_extent_compression(leaf, fi, 0);
+        btrfs_set_file_extent_encryption(leaf, fi, 0);
+        btrfs_set_file_extent_other_encoding(leaf, fi, 0);
+
+        ret = btrfs_inc_extent_ref(trans, root, bytenr, num_bytes,
+                                   leaf->start, root->root_key.objectid,
+                                   trans->transid, inode->i_ino);
+        BUG_ON(ret);
+done:
+        btrfs_mark_buffer_dirty(leaf);
+        btrfs_release_path(root, path);
+        if (split_end && split == start) {
+                split = end;
+                goto again;
+        }
+        if (locked_end > end) {
+                unlock_extent(&BTRFS_I(inode)->io_tree, end, locked_end - 1,
+                              GFP_NOFS);
+        }
+        btrfs_free_path(path);
+        return 0;
+}
+
 /*
  * this gets pages into the page cache and locks them down, it also properly
  * waits for data=ordered extents to finish before allowing the pages to be