Btrfs: Update on disk i_size only after pending ordered extents are done

This changes the ordered data code to update i_size after the extent
is on disk.  An on disk i_size is maintained in the in-memory btrfs inode
structures, and this is updated as extents finish.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 89 insertions, 0 deletions

diff --git a/fs/btrfs/ordered-data.c b/fs/btrfs/ordered-data.c
index 6513270f054c..d86a953ae51d 100644
--- a/fs/btrfs/ordered-data.c
+++ b/fs/btrfs/ordered-data.c
@@ -406,3 +406,92 @@ out:
         mutex_unlock(&tree->mutex);
         return entry;
 }
+
+int btrfs_ordered_update_i_size(struct inode *inode,
+                                struct btrfs_ordered_extent *ordered)
+{
+        struct btrfs_ordered_inode_tree *tree = &BTRFS_I(inode)->ordered_tree;
+        struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
+        u64 disk_i_size;
+        u64 new_i_size;
+        u64 i_size_test;
+        struct rb_node *node;
+        struct btrfs_ordered_extent *test;
+
+        mutex_lock(&tree->mutex);
+        disk_i_size = BTRFS_I(inode)->disk_i_size;
+
+        /*
+         * if the disk i_size is already at the inode->i_size, or
+         * this ordered extent is inside the disk i_size, we're done
+         */
+        if (disk_i_size >= inode->i_size ||
+            ordered->file_offset + ordered->len <= disk_i_size) {
+                goto out;
+        }
+
+        /*
+         * we can't update the disk_isize if there are delalloc bytes
+         * between disk_i_size and  this ordered extent
+         */
+        if (test_range_bit(io_tree, disk_i_size,
+                           ordered->file_offset + ordered->len - 1,
+                           EXTENT_DELALLOC, 0)) {
+                goto out;
+        }
+        /*
+         * walk backward from this ordered extent to disk_i_size.
+         * if we find an ordered extent then we can't update disk i_size
+         * yet
+         */
+        while(1) {
+                node = rb_prev(&ordered->rb_node);
+                if (!node)
+                        break;
+                test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
+                if (test->file_offset + test->len <= disk_i_size)
+                        break;
+                if (test->file_offset >= inode->i_size)
+                        break;
+                if (test->file_offset >= disk_i_size)
+                        goto out;
+        }
+        new_i_size = min_t(u64, entry_end(ordered), i_size_read(inode));
+
+        /*
+         * at this point, we know we can safely update i_size to at least
+         * the offset from this ordered extent.  But, we need to
+         * walk forward and see if ios from higher up in the file have
+         * finished.
+         */
+        node = rb_next(&ordered->rb_node);
+        i_size_test = 0;
+        if (node) {
+                /*
+                 * do we have an area where IO might have finished
+                 * between our ordered extent and the next one.
+                 */
+                test = rb_entry(node, struct btrfs_ordered_extent, rb_node);
+                if (test->file_offset > entry_end(ordered)) {
+                        i_size_test = test->file_offset - 1;
+                }
+        } else {
+                i_size_test = i_size_read(inode);
+        }
+
+        /*
+         * i_size_test is the end of a region after this ordered
+         * extent where there are no ordered extents.  As long as there
+         * are no delalloc bytes in this area, it is safe to update
+         * disk_i_size to the end of the region.
+         */
+        if (i_size_test > entry_end(ordered) &&
+            !test_range_bit(io_tree, entry_end(ordered), i_size_test,
+                           EXTENT_DELALLOC, 0)) {
+                new_i_size = min_t(u64, i_size_test, i_size_read(inode));
+        }
+        BTRFS_I(inode)->disk_i_size = new_i_size;
+out:
+        mutex_unlock(&tree->mutex);
+        return 0;
+}