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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>
This commit is contained in:
David Sterba 2016-04-27 02:15:15 +02:00
parent 8eb0dfdbda
commit 6ac10a6ac2
1 changed files with 19 additions and 16 deletions
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35
fs/btrfs/compression.c
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@ -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);
}
}
}