btrfs: Introduce find_free_extent_ctl structure for later rework
authorQu Wenruo <wqu@suse.com>
Fri, 2 Nov 2018 01:39:47 +0000 (09:39 +0800)
committerDavid Sterba <dsterba@suse.com>
Mon, 17 Dec 2018 13:51:26 +0000 (14:51 +0100)
Instead of tons of different local variables in find_free_extent(),
extract them into find_free_extent_ctl structure, and add better
explanation for them.

Some modification may looks redundant, but will later greatly simplify
function parameter list during find_free_extent() refactor.

Also add two comments to co-operate with fb5c39d7a887 ("btrfs: don't use
ctl->free_space for max_extent_size"), to make ffe_ctl->max_extent_size
update more reader-friendly.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Su Yue <suy.fnst@cn.fujitsu.com>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
fs/btrfs/extent-tree.c

index 71ab8d9d23643e2cef117660ddc7b3d5d3dfcf41..43b38ee9870d0abce7d8aa61f40d6c968b86d135 100644 (file)
@@ -7253,6 +7253,58 @@ btrfs_release_block_group(struct btrfs_block_group_cache *cache,
        btrfs_put_block_group(cache);
 }
 
+/*
+ * Structure used internally for find_free_extent() function.  Wraps needed
+ * parameters.
+ */
+struct find_free_extent_ctl {
+       /* Basic allocation info */
+       u64 ram_bytes;
+       u64 num_bytes;
+       u64 empty_size;
+       u64 flags;
+       int delalloc;
+
+       /* Where to start the search inside the bg */
+       u64 search_start;
+
+       /* For clustered allocation */
+       u64 empty_cluster;
+
+       bool have_caching_bg;
+       bool orig_have_caching_bg;
+
+       /* RAID index, converted from flags */
+       int index;
+
+       /* Current loop number */
+       int loop;
+
+       /*
+        * Whether we're refilling a cluster, if true we need to re-search
+        * current block group but don't try to refill the cluster again.
+        */
+       bool retry_clustered;
+
+       /*
+        * Whether we're updating free space cache, if true we need to re-search
+        * current block group but don't try updating free space cache again.
+        */
+       bool retry_unclustered;
+
+       /* If current block group is cached */
+       int cached;
+
+       /* Max contiguous hole found */
+       u64 max_extent_size;
+
+       /* Total free space from free space cache, not always contiguous */
+       u64 total_free_space;
+
+       /* Found result */
+       u64 found_offset;
+};
+
 /*
  * walks the btree of allocated extents and find a hole of a given size.
  * The key ins is changed to record the hole:
@@ -7273,21 +7325,26 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
        struct btrfs_root *root = fs_info->extent_root;
        struct btrfs_free_cluster *last_ptr = NULL;
        struct btrfs_block_group_cache *block_group = NULL;
-       u64 search_start = 0;
-       u64 max_extent_size = 0;
-       u64 max_free_space = 0;
-       u64 empty_cluster = 0;
+       struct find_free_extent_ctl ffe_ctl = {0};
        struct btrfs_space_info *space_info;
-       int loop = 0;
-       int index = btrfs_bg_flags_to_raid_index(flags);
-       bool failed_cluster_refill = false;
-       bool failed_alloc = false;
        bool use_cluster = true;
-       bool have_caching_bg = false;
-       bool orig_have_caching_bg = false;
        bool full_search = false;
 
        WARN_ON(num_bytes < fs_info->sectorsize);
+
+       ffe_ctl.ram_bytes = ram_bytes;
+       ffe_ctl.num_bytes = num_bytes;
+       ffe_ctl.empty_size = empty_size;
+       ffe_ctl.flags = flags;
+       ffe_ctl.search_start = 0;
+       ffe_ctl.retry_clustered = false;
+       ffe_ctl.retry_unclustered = false;
+       ffe_ctl.delalloc = delalloc;
+       ffe_ctl.index = btrfs_bg_flags_to_raid_index(flags);
+       ffe_ctl.have_caching_bg = false;
+       ffe_ctl.orig_have_caching_bg = false;
+       ffe_ctl.found_offset = 0;
+
        ins->type = BTRFS_EXTENT_ITEM_KEY;
        ins->objectid = 0;
        ins->offset = 0;
@@ -7323,7 +7380,8 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
                spin_unlock(&space_info->lock);
        }
 
-       last_ptr = fetch_cluster_info(fs_info, space_info, &empty_cluster);
+       last_ptr = fetch_cluster_info(fs_info, space_info,
+                                     &ffe_ctl.empty_cluster);
        if (last_ptr) {
                spin_lock(&last_ptr->lock);
                if (last_ptr->block_group)
@@ -7340,10 +7398,12 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
                spin_unlock(&last_ptr->lock);
        }
 
-       search_start = max(search_start, first_logical_byte(fs_info, 0));
-       search_start = max(search_start, hint_byte);
-       if (search_start == hint_byte) {
-               block_group = btrfs_lookup_block_group(fs_info, search_start);
+       ffe_ctl.search_start = max(ffe_ctl.search_start,
+                                  first_logical_byte(fs_info, 0));
+       ffe_ctl.search_start = max(ffe_ctl.search_start, hint_byte);
+       if (ffe_ctl.search_start == hint_byte) {
+               block_group = btrfs_lookup_block_group(fs_info,
+                                                      ffe_ctl.search_start);
                /*
                 * we don't want to use the block group if it doesn't match our
                 * allocation bits, or if its not cached.
@@ -7365,7 +7425,7 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
                                btrfs_put_block_group(block_group);
                                up_read(&space_info->groups_sem);
                        } else {
-                               index = btrfs_bg_flags_to_raid_index(
+                               ffe_ctl.index = btrfs_bg_flags_to_raid_index(
                                                block_group->flags);
                                btrfs_lock_block_group(block_group, delalloc);
                                goto have_block_group;
@@ -7375,21 +7435,19 @@ static noinline int find_free_extent(struct btrfs_fs_info *fs_info,
                }
        }
 search:
-       have_caching_bg = false;
-       if (index == 0 || index == btrfs_bg_flags_to_raid_index(flags))
+       ffe_ctl.have_caching_bg = false;
+       if (ffe_ctl.index == btrfs_bg_flags_to_raid_index(flags) ||
+           ffe_ctl.index == 0)
                full_search = true;
        down_read(&space_info->groups_sem);
-       list_for_each_entry(block_group, &space_info->block_groups[index],
-                           list) {
-               u64 offset;
-               int cached;
-
+       list_for_each_entry(block_group,
+                           &space_info->block_groups[ffe_ctl.index], list) {
                /* If the block group is read-only, we can skip it entirely. */
                if (unlikely(block_group->ro))
                        continue;
 
                btrfs_grab_block_group(block_group, delalloc);
-               search_start = block_group->key.objectid;
+               ffe_ctl.search_start = block_group->key.objectid;
 
                /*
                 * this can happen if we end up cycling through all the
@@ -7413,9 +7471,9 @@ search:
                }
 
 have_block_group:
-               cached = block_group_cache_done(block_group);
-               if (unlikely(!cached)) {
-                       have_caching_bg = true;
+               ffe_ctl.cached = block_group_cache_done(block_group);
+               if (unlikely(!ffe_ctl.cached)) {
+                       ffe_ctl.have_caching_bg = true;
                        ret = cache_block_group(block_group, 0);
                        BUG_ON(ret < 0);
                        ret = 0;
@@ -7443,20 +7501,23 @@ have_block_group:
 
                        if (used_block_group != block_group &&
                            (used_block_group->ro ||
-                            !block_group_bits(used_block_group, flags)))
+                            !block_group_bits(used_block_group,
+                                              ffe_ctl.flags)))
                                goto release_cluster;
 
-                       offset = btrfs_alloc_from_cluster(used_block_group,
+                       ffe_ctl.found_offset = btrfs_alloc_from_cluster(
+                                               used_block_group,
                                                last_ptr,
                                                num_bytes,
                                                used_block_group->key.objectid,
-                                               &max_extent_size);
-                       if (offset) {
+                                               &ffe_ctl.max_extent_size);
+                       if (ffe_ctl.found_offset) {
                                /* we have a block, we're done */
                                spin_unlock(&last_ptr->refill_lock);
                                trace_btrfs_reserve_extent_cluster(
                                                used_block_group,
-                                               search_start, num_bytes);
+                                               ffe_ctl.search_start,
+                                               num_bytes);
                                if (used_block_group != block_group) {
                                        btrfs_release_block_group(block_group,
                                                                  delalloc);
@@ -7482,7 +7543,7 @@ release_cluster:
                         * first, so that we stand a better chance of
                         * succeeding in the unclustered
                         * allocation.  */
-                       if (loop >= LOOP_NO_EMPTY_SIZE &&
+                       if (ffe_ctl.loop >= LOOP_NO_EMPTY_SIZE &&
                            used_block_group != block_group) {
                                spin_unlock(&last_ptr->refill_lock);
                                btrfs_release_block_group(used_block_group,
@@ -7500,18 +7561,19 @@ release_cluster:
                                btrfs_release_block_group(used_block_group,
                                                          delalloc);
 refill_cluster:
-                       if (loop >= LOOP_NO_EMPTY_SIZE) {
+                       if (ffe_ctl.loop >= LOOP_NO_EMPTY_SIZE) {
                                spin_unlock(&last_ptr->refill_lock);
                                goto unclustered_alloc;
                        }
 
                        aligned_cluster = max_t(unsigned long,
-                                               empty_cluster + empty_size,
-                                             block_group->full_stripe_len);
+                                       ffe_ctl.empty_cluster + empty_size,
+                                       block_group->full_stripe_len);
 
                        /* allocate a cluster in this block group */
                        ret = btrfs_find_space_cluster(fs_info, block_group,
-                                                      last_ptr, search_start,
+                                                      last_ptr,
+                                                      ffe_ctl.search_start,
                                                       num_bytes,
                                                       aligned_cluster);
                        if (ret == 0) {
@@ -7519,26 +7581,28 @@ refill_cluster:
                                 * now pull our allocation out of this
                                 * cluster
                                 */
-                               offset = btrfs_alloc_from_cluster(block_group,
-                                                       last_ptr,
-                                                       num_bytes,
-                                                       search_start,
-                                                       &max_extent_size);
-                               if (offset) {
+                               ffe_ctl.found_offset = btrfs_alloc_from_cluster(
+                                               block_group, last_ptr,
+                                               num_bytes, ffe_ctl.search_start,
+                                               &ffe_ctl.max_extent_size);
+                               if (ffe_ctl.found_offset) {
                                        /* we found one, proceed */
                                        spin_unlock(&last_ptr->refill_lock);
                                        trace_btrfs_reserve_extent_cluster(
-                                               block_group, search_start,
+                                               block_group,
+                                               ffe_ctl.search_start,
                                                num_bytes);
                                        goto checks;
                                }
-                       } else if (!cached && loop > LOOP_CACHING_NOWAIT
-                                  && !failed_cluster_refill) {
+                       } else if (!ffe_ctl.cached &&
+                                  ffe_ctl.loop > LOOP_CACHING_NOWAIT &&
+                                  !ffe_ctl.retry_clustered) {
                                spin_unlock(&last_ptr->refill_lock);
 
-                               failed_cluster_refill = true;
+                               ffe_ctl.retry_clustered = true;
                                wait_block_group_cache_progress(block_group,
-                                      num_bytes + empty_cluster + empty_size);
+                                      num_bytes + ffe_ctl.empty_cluster +
+                                      empty_size);
                                goto have_block_group;
                        }
 
@@ -7564,89 +7628,96 @@ unclustered_alloc:
                        last_ptr->fragmented = 1;
                        spin_unlock(&last_ptr->lock);
                }
-               if (cached) {
+               if (ffe_ctl.cached) {
                        struct btrfs_free_space_ctl *ctl =
                                block_group->free_space_ctl;
 
                        spin_lock(&ctl->tree_lock);
                        if (ctl->free_space <
-                           num_bytes + empty_cluster + empty_size) {
-                               max_free_space = max(max_free_space,
-                                                    ctl->free_space);
+                           num_bytes + ffe_ctl.empty_cluster + empty_size) {
+                               ffe_ctl.total_free_space = max(ctl->free_space,
+                                               ffe_ctl.total_free_space);
                                spin_unlock(&ctl->tree_lock);
                                goto loop;
                        }
                        spin_unlock(&ctl->tree_lock);
                }
 
-               offset = btrfs_find_space_for_alloc(block_group, search_start,
-                                                   num_bytes, empty_size,
-                                                   &max_extent_size);
+               ffe_ctl.found_offset = btrfs_find_space_for_alloc(block_group,
+                               ffe_ctl.search_start, num_bytes, empty_size,
+                               &ffe_ctl.max_extent_size);
                /*
                 * If we didn't find a chunk, and we haven't failed on this
                 * block group before, and this block group is in the middle of
                 * caching and we are ok with waiting, then go ahead and wait
-                * for progress to be made, and set failed_alloc to true.
+                * for progress to be made, and set ffe_ctl.retry_unclustered to
+                * true.
                 *
-                * If failed_alloc is true then we've already waited on this
-                * block group once and should move on to the next block group.
+                * If ffe_ctl.retry_unclustered is true then we've already
+                * waited on this block group once and should move on to the
+                * next block group.
                 */
-               if (!offset && !failed_alloc && !cached &&
-                   loop > LOOP_CACHING_NOWAIT) {
+               if (!ffe_ctl.found_offset && !ffe_ctl.retry_unclustered &&
+                   !ffe_ctl.cached && ffe_ctl.loop > LOOP_CACHING_NOWAIT) {
                        wait_block_group_cache_progress(block_group,
                                                num_bytes + empty_size);
-                       failed_alloc = true;
+                       ffe_ctl.retry_unclustered = true;
                        goto have_block_group;
-               } else if (!offset) {
+               } else if (!ffe_ctl.found_offset) {
                        goto loop;
                }
 checks:
-               search_start = round_up(offset, fs_info->stripesize);
+               ffe_ctl.search_start = round_up(ffe_ctl.found_offset,
+                                            fs_info->stripesize);
 
                /* move on to the next group */
-               if (search_start + num_bytes >
+               if (ffe_ctl.search_start + num_bytes >
                    block_group->key.objectid + block_group->key.offset) {
-                       btrfs_add_free_space(block_group, offset, num_bytes);
+                       btrfs_add_free_space(block_group, ffe_ctl.found_offset,
+                                            num_bytes);
                        goto loop;
                }
 
-               if (offset < search_start)
-                       btrfs_add_free_space(block_group, offset,
-                                            search_start - offset);
+               if (ffe_ctl.found_offset < ffe_ctl.search_start)
+                       btrfs_add_free_space(block_group, ffe_ctl.found_offset,
+                               ffe_ctl.search_start - ffe_ctl.found_offset);
 
                ret = btrfs_add_reserved_bytes(block_group, ram_bytes,
                                num_bytes, delalloc);
                if (ret == -EAGAIN) {
-                       btrfs_add_free_space(block_group, offset, num_bytes);
+                       btrfs_add_free_space(block_group, ffe_ctl.found_offset,
+                                            num_bytes);
                        goto loop;
                }
                btrfs_inc_block_group_reservations(block_group);
 
                /* we are all good, lets return */
-               ins->objectid = search_start;
+               ins->objectid = ffe_ctl.search_start;
                ins->offset = num_bytes;
 
-               trace_btrfs_reserve_extent(block_group, search_start, num_bytes);
+               trace_btrfs_reserve_extent(block_group, ffe_ctl.search_start,
+                                          num_bytes);
                btrfs_release_block_group(block_group, delalloc);
                break;
 loop:
-               failed_cluster_refill = false;
-               failed_alloc = false;
+               ffe_ctl.retry_clustered = false;
+               ffe_ctl.retry_unclustered = false;
                BUG_ON(btrfs_bg_flags_to_raid_index(block_group->flags) !=
-                      index);
+                      ffe_ctl.index);
                btrfs_release_block_group(block_group, delalloc);
                cond_resched();
        }
        up_read(&space_info->groups_sem);
 
-       if ((loop == LOOP_CACHING_NOWAIT) && have_caching_bg
-               && !orig_have_caching_bg)
-               orig_have_caching_bg = true;
+       if ((ffe_ctl.loop == LOOP_CACHING_NOWAIT) && ffe_ctl.have_caching_bg
+               && !ffe_ctl.orig_have_caching_bg)
+               ffe_ctl.orig_have_caching_bg = true;
 
-       if (!ins->objectid && loop >= LOOP_CACHING_WAIT && have_caching_bg)
+       if (!ins->objectid && ffe_ctl.loop >= LOOP_CACHING_WAIT &&
+           ffe_ctl.have_caching_bg)
                goto search;
 
-       if (!ins->objectid && ++index < BTRFS_NR_RAID_TYPES)
+       if (!ins->objectid && ++ffe_ctl.index < BTRFS_NR_RAID_TYPES)
                goto search;
 
        /*
@@ -7657,23 +7728,23 @@ loop:
         * LOOP_NO_EMPTY_SIZE, set empty_size and empty_cluster to 0 and try
         *                      again
         */
-       if (!ins->objectid && loop < LOOP_NO_EMPTY_SIZE) {
-               index = 0;
-               if (loop == LOOP_CACHING_NOWAIT) {
+       if (!ins->objectid && ffe_ctl.loop < LOOP_NO_EMPTY_SIZE) {
+               ffe_ctl.index = 0;
+               if (ffe_ctl.loop == LOOP_CACHING_NOWAIT) {
                        /*
                         * We want to skip the LOOP_CACHING_WAIT step if we
                         * don't have any uncached bgs and we've already done a
                         * full search through.
                         */
-                       if (orig_have_caching_bg || !full_search)
-                               loop = LOOP_CACHING_WAIT;
+                       if (ffe_ctl.orig_have_caching_bg || !full_search)
+                               ffe_ctl.loop = LOOP_CACHING_WAIT;
                        else
-                               loop = LOOP_ALLOC_CHUNK;
+                               ffe_ctl.loop = LOOP_ALLOC_CHUNK;
                } else {
-                       loop++;
+                       ffe_ctl.loop++;
                }
 
-               if (loop == LOOP_ALLOC_CHUNK) {
+               if (ffe_ctl.loop == LOOP_ALLOC_CHUNK) {
                        struct btrfs_trans_handle *trans;
                        int exist = 0;
 
@@ -7696,7 +7767,7 @@ loop:
                         * case.
                         */
                        if (ret == -ENOSPC)
-                               loop = LOOP_NO_EMPTY_SIZE;
+                               ffe_ctl.loop = LOOP_NO_EMPTY_SIZE;
 
                        /*
                         * Do not bail out on ENOSPC since we
@@ -7712,18 +7783,18 @@ loop:
                                goto out;
                }
 
-               if (loop == LOOP_NO_EMPTY_SIZE) {
+               if (ffe_ctl.loop == LOOP_NO_EMPTY_SIZE) {
                        /*
                         * Don't loop again if we already have no empty_size and
                         * no empty_cluster.
                         */
                        if (empty_size == 0 &&
-                           empty_cluster == 0) {
+                           ffe_ctl.empty_cluster == 0) {
                                ret = -ENOSPC;
                                goto out;
                        }
                        empty_size = 0;
-                       empty_cluster = 0;
+                       ffe_ctl.empty_cluster = 0;
                }
 
                goto search;
@@ -7739,12 +7810,16 @@ loop:
        }
 out:
        if (ret == -ENOSPC) {
-               if (!max_extent_size)
-                       max_extent_size = max_free_space;
+               /*
+                * Use ffe_ctl->total_free_space as fallback if we can't find
+                * any contiguous hole.
+                */
+               if (!ffe_ctl.max_extent_size)
+                       ffe_ctl.max_extent_size = ffe_ctl.total_free_space;
                spin_lock(&space_info->lock);
-               space_info->max_extent_size = max_extent_size;
+               space_info->max_extent_size = ffe_ctl.max_extent_size;
                spin_unlock(&space_info->lock);
-               ins->offset = max_extent_size;
+               ins->offset = ffe_ctl.max_extent_size;
        }
        return ret;
 }