btrfs: rename and document compression workspace members

The names are confusing, pick more fitting names and add comments.

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index ff61a41..4d5cd96 100644 (file)
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -743,8 +743,11 @@ out:
 static struct {
        struct list_head idle_ws;
        spinlock_t ws_lock;
-       int num_ws;
-       atomic_t alloc_ws;
+       /* Number of free workspaces */
+       int free_ws;
+       /* Total number of allocated workspaces */
+       atomic_t total_ws;
+       /* Waiters for a free workspace */
        wait_queue_head_t ws_wait;
 } btrfs_comp_ws[BTRFS_COMPRESS_TYPES];
 
@@ -760,7 +763,7 @@ void __init btrfs_init_compress(void)
        for (i = 0; i < BTRFS_COMPRESS_TYPES; i++) {
                INIT_LIST_HEAD(&btrfs_comp_ws[i].idle_ws);
                spin_lock_init(&btrfs_comp_ws[i].ws_lock);
-               atomic_set(&btrfs_comp_ws[i].alloc_ws, 0);
+               atomic_set(&btrfs_comp_ws[i].total_ws, 0);
                init_waitqueue_head(&btrfs_comp_ws[i].ws_wait);
        }
 }
@@ -777,35 +780,35 @@ static struct list_head *find_workspace(int type)
 
        struct list_head *idle_ws       = &btrfs_comp_ws[idx].idle_ws;
        spinlock_t *ws_lock             = &btrfs_comp_ws[idx].ws_lock;
-       atomic_t *alloc_ws              = &btrfs_comp_ws[idx].alloc_ws;
+       atomic_t *total_ws              = &btrfs_comp_ws[idx].total_ws;
        wait_queue_head_t *ws_wait      = &btrfs_comp_ws[idx].ws_wait;
-       int *num_ws                     = &btrfs_comp_ws[idx].num_ws;
+       int *free_ws                    = &btrfs_comp_ws[idx].free_ws;
 again:
        spin_lock(ws_lock);
        if (!list_empty(idle_ws)) {
                workspace = idle_ws->next;
                list_del(workspace);
-               (*num_ws)--;
+               (*free_ws)--;
                spin_unlock(ws_lock);
                return workspace;
 
        }
-       if (atomic_read(alloc_ws) > cpus) {
+       if (atomic_read(total_ws) > cpus) {
                DEFINE_WAIT(wait);
 
                spin_unlock(ws_lock);
                prepare_to_wait(ws_wait, &wait, TASK_UNINTERRUPTIBLE);
-               if (atomic_read(alloc_ws) > cpus && !*num_ws)
+               if (atomic_read(total_ws) > cpus && !*free_ws)
                        schedule();
                finish_wait(ws_wait, &wait);
                goto again;
        }
-       atomic_inc(alloc_ws);
+       atomic_inc(total_ws);
        spin_unlock(ws_lock);
 
        workspace = btrfs_compress_op[idx]->alloc_workspace();
        if (IS_ERR(workspace)) {
-               atomic_dec(alloc_ws);
+               atomic_dec(total_ws);
                wake_up(ws_wait);
        }
        return workspace;
@@ -820,21 +823,21 @@ static void free_workspace(int type, struct list_head *workspace)
        int idx = type - 1;
        struct list_head *idle_ws       = &btrfs_comp_ws[idx].idle_ws;
        spinlock_t *ws_lock             = &btrfs_comp_ws[idx].ws_lock;
-       atomic_t *alloc_ws              = &btrfs_comp_ws[idx].alloc_ws;
+       atomic_t *total_ws              = &btrfs_comp_ws[idx].total_ws;
        wait_queue_head_t *ws_wait      = &btrfs_comp_ws[idx].ws_wait;
-       int *num_ws                     = &btrfs_comp_ws[idx].num_ws;
+       int *free_ws                    = &btrfs_comp_ws[idx].free_ws;
 
        spin_lock(ws_lock);
-       if (*num_ws < num_online_cpus()) {
+       if (*free_ws < num_online_cpus()) {
                list_add(workspace, idle_ws);
-               (*num_ws)++;
+               (*free_ws)++;
                spin_unlock(ws_lock);
                goto wake;
        }
        spin_unlock(ws_lock);
 
        btrfs_compress_op[idx]->free_workspace(workspace);
-       atomic_dec(alloc_ws);
+       atomic_dec(total_ws);
 wake:
        /*
         * Make sure counter is updated before we wake up waiters.
@@ -857,7 +860,7 @@ static void free_workspaces(void)
                        workspace = btrfs_comp_ws[i].idle_ws.next;
                        list_del(workspace);
                        btrfs_compress_op[i]->free_workspace(workspace);
-                       atomic_dec(&btrfs_comp_ws[i].alloc_ws);
+                       atomic_dec(&btrfs_comp_ws[i].total_ws);
                }
        }
 }