There are two levels of workspace management. First, alloc()/free()
which are responsible for actually creating and destroy workspaces.
Second, at a higher level, get()/put() which is the compression code
asking for a workspace from a workspace_manager.

The compression code shouldn't really care how it gets a workspace, but
that it got a workspace. This adds get_workspace() and put_workspace()
to be the higher level interface which is responsible for indexing into
the appropriate compression type. It also introduces
btrfs_put_workspace() and btrfs_get_workspace() to be the generic
implementations of the higher interface.

Signed-off-by: Dennis Zhou <den...@kernel.org>
Reviewed-by: Josef Bacik <jo...@toxicpanda.com>
---
 fs/btrfs/compression.c | 57 +++++++++++++++++++++++++-----------------
 1 file changed, 34 insertions(+), 23 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index b213d1efb586..98e1b222f78c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -839,7 +839,7 @@ static void btrfs_cleanup_workspace_manager(struct 
workspace_manager *wsman)
  * Preallocation makes a forward progress guarantees and we do not return
  * errors.
  */
-static struct list_head *find_workspace(int type)
+static struct list_head *btrfs_get_workspace(struct workspace_manager *wsman)
 {
        struct list_head *workspace;
        int cpus = num_online_cpus();
@@ -850,11 +850,11 @@ static struct list_head *find_workspace(int type)
        wait_queue_head_t *ws_wait;
        int *free_ws;
 
-       idle_ws  = &wsm[type].idle_ws;
-       ws_lock  = &wsm[type].ws_lock;
-       total_ws = &wsm[type].total_ws;
-       ws_wait  = &wsm[type].ws_wait;
-       free_ws  = &wsm[type].free_ws;
+       idle_ws  = &wsman->idle_ws;
+       ws_lock  = &wsman->ws_lock;
+       total_ws = &wsman->total_ws;
+       ws_wait  = &wsman->ws_wait;
+       free_ws  = &wsman->free_ws;
 
 again:
        spin_lock(ws_lock);
@@ -885,7 +885,7 @@ static struct list_head *find_workspace(int type)
         * context of btrfs_compress_bio/btrfs_compress_pages
         */
        nofs_flag = memalloc_nofs_save();
-       workspace = wsm[type].ops->alloc_workspace();
+       workspace = wsman->ops->alloc_workspace();
        memalloc_nofs_restore(nofs_flag);
 
        if (IS_ERR(workspace)) {
@@ -916,11 +916,17 @@ static struct list_head *find_workspace(int type)
        return workspace;
 }
 
+static struct list_head *get_workspace(int type)
+{
+       return btrfs_get_workspace(&wsm[type]);
+}
+
 /*
  * put a workspace struct back on the list or free it if we have enough
  * idle ones sitting around
  */
-static void free_workspace(int type, struct list_head *workspace)
+static void btrfs_put_workspace(struct workspace_manager *wsman,
+                               struct list_head *ws)
 {
        struct list_head *idle_ws;
        spinlock_t *ws_lock;
@@ -928,27 +934,32 @@ static void free_workspace(int type, struct list_head 
*workspace)
        wait_queue_head_t *ws_wait;
        int *free_ws;
 
-       idle_ws  = &wsm[type].idle_ws;
-       ws_lock  = &wsm[type].ws_lock;
-       total_ws = &wsm[type].total_ws;
-       ws_wait  = &wsm[type].ws_wait;
-       free_ws  = &wsm[type].free_ws;
+       idle_ws  = &wsman->idle_ws;
+       ws_lock  = &wsman->ws_lock;
+       total_ws = &wsman->total_ws;
+       ws_wait  = &wsman->ws_wait;
+       free_ws  = &wsman->free_ws;
 
        spin_lock(ws_lock);
        if (*free_ws <= num_online_cpus()) {
-               list_add(workspace, idle_ws);
+               list_add(ws, idle_ws);
                (*free_ws)++;
                spin_unlock(ws_lock);
                goto wake;
        }
        spin_unlock(ws_lock);
 
-       wsm[type].ops->free_workspace(workspace);
+       wsman->ops->free_workspace(ws);
        atomic_dec(total_ws);
 wake:
        cond_wake_up(ws_wait);
 }
 
+static void put_workspace(int type, struct list_head *ws)
+{
+       return btrfs_put_workspace(&wsm[type], ws);
+}
+
 /*
  * Given an address space and start and length, compress the bytes into @pages
  * that are allocated on demand.
@@ -982,14 +993,14 @@ int btrfs_compress_pages(unsigned int type_level, struct 
address_space *mapping,
        struct list_head *workspace;
        int ret;
 
-       workspace = find_workspace(type);
+       workspace = get_workspace(type);
 
        btrfs_compress_op[type]->set_level(workspace, type_level);
        ret = btrfs_compress_op[type]->compress_pages(workspace, mapping,
                                                      start, pages,
                                                      out_pages,
                                                      total_in, total_out);
-       free_workspace(type, workspace);
+       put_workspace(type, workspace);
        return ret;
 }
 
@@ -1013,9 +1024,9 @@ static int btrfs_decompress_bio(struct compressed_bio *cb)
        int ret;
        int type = cb->compress_type;
 
-       workspace = find_workspace(type);
+       workspace = get_workspace(type);
        ret = btrfs_compress_op[type]->decompress_bio(workspace, cb);
-       free_workspace(type, workspace);
+       put_workspace(type, workspace);
 
        return ret;
 }
@@ -1031,13 +1042,13 @@ int btrfs_decompress(int type, unsigned char *data_in, 
struct page *dest_page,
        struct list_head *workspace;
        int ret;
 
-       workspace = find_workspace(type);
+       workspace = get_workspace(type);
 
        ret = btrfs_compress_op[type]->decompress(workspace, data_in,
                                                  dest_page, start_byte,
                                                  srclen, destlen);
 
-       free_workspace(type, workspace);
+       put_workspace(type, workspace);
        return ret;
 }
 
@@ -1465,7 +1476,7 @@ static void heuristic_collect_sample(struct inode *inode, 
u64 start, u64 end,
  */
 int btrfs_compress_heuristic(struct inode *inode, u64 start, u64 end)
 {
-       struct list_head *ws_list = find_workspace(0);
+       struct list_head *ws_list = get_workspace(0);
        struct heuristic_ws *ws;
        u32 i;
        u8 byte;
@@ -1534,7 +1545,7 @@ int btrfs_compress_heuristic(struct inode *inode, u64 
start, u64 end)
        }
 
 out:
-       free_workspace(0, ws_list);
+       put_workspace(0, ws_list);
        return ret;
 }
 
-- 
2.17.1

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