btrfs: refactor find_free_dev_extent_start()

Factor out two functions from find_free_dev_extent_start().
dev_extent_search_start() decides the starting position of the search.
dev_extent_hole_check() checks if a hole found is suitable for device
extent allocation.

These functions also have the switch-cases to change the allocation
behavior depending on the policy.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index e4a2d96..d126e7d 100644 (file)
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1381,6 +1381,59 @@ static bool contains_pending_extent(struct btrfs_device *device, u64 *start,
        return false;
 }
 
+static u64 dev_extent_search_start(struct btrfs_device *device, u64 start)
+{
+       switch (device->fs_devices->chunk_alloc_policy) {
+       case BTRFS_CHUNK_ALLOC_REGULAR:
+               /*
+                * We don't want to overwrite the superblock on the drive nor
+                * any area used by the boot loader (grub for example), so we
+                * make sure to start at an offset of at least 1MB.
+                */
+               return max_t(u64, start, SZ_1M);
+       default:
+               BUG();
+       }
+}
+
+/**
+ * dev_extent_hole_check - check if specified hole is suitable for allocation
+ * @device:    the device which we have the hole
+ * @hole_start: starting position of the hole
+ * @hole_size: the size of the hole
+ * @num_bytes: the size of the free space that we need
+ *
+ * This function may modify @hole_start and @hole_end to reflect the suitable
+ * position for allocation. Returns 1 if hole position is updated, 0 otherwise.
+ */
+static bool dev_extent_hole_check(struct btrfs_device *device, u64 *hole_start,
+                                 u64 *hole_size, u64 num_bytes)
+{
+       bool changed = false;
+       u64 hole_end = *hole_start + *hole_size;
+
+       /*
+        * Check before we set max_hole_start, otherwise we could end up
+        * sending back this offset anyway.
+        */
+       if (contains_pending_extent(device, hole_start, *hole_size)) {
+               if (hole_end >= *hole_start)
+                       *hole_size = hole_end - *hole_start;
+               else
+                       *hole_size = 0;
+               changed = true;
+       }
+
+       switch (device->fs_devices->chunk_alloc_policy) {
+       case BTRFS_CHUNK_ALLOC_REGULAR:
+               /* No extra check */
+               break;
+       default:
+               BUG();
+       }
+
+       return changed;
+}
 
 /*
  * find_free_dev_extent_start - find free space in the specified device
@@ -1427,12 +1480,7 @@ static int find_free_dev_extent_start(struct btrfs_device *device,
        int slot;
        struct extent_buffer *l;
 
-       /*
-        * We don't want to overwrite the superblock on the drive nor any area
-        * used by the boot loader (grub for example), so we make sure to start
-        * at an offset of at least 1MB.
-        */
-       search_start = max_t(u64, search_start, SZ_1M);
+       search_start = dev_extent_search_start(device, search_start);
 
        path = btrfs_alloc_path();
        if (!path)
@@ -1490,18 +1538,8 @@ again:
 
                if (key.offset > search_start) {
                        hole_size = key.offset - search_start;
-
-                       /*
-                        * Have to check before we set max_hole_start, otherwise
-                        * we could end up sending back this offset anyway.
-                        */
-                       if (contains_pending_extent(device, &search_start,
-                                                   hole_size)) {
-                               if (key.offset >= search_start)
-                                       hole_size = key.offset - search_start;
-                               else
-                                       hole_size = 0;
-                       }
+                       dev_extent_hole_check(device, &search_start, &hole_size,
+                                             num_bytes);
 
                        if (hole_size > max_hole_size) {
                                max_hole_start = search_start;
@@ -1540,8 +1578,8 @@ next:
         */
        if (search_end > search_start) {
                hole_size = search_end - search_start;
-
-               if (contains_pending_extent(device, &search_start, hole_size)) {
+               if (dev_extent_hole_check(device, &search_start, &hole_size,
+                                         num_bytes)) {
                        btrfs_release_path(path);
                        goto again;
                }