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dm-bufio: clean-up cache size reading

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In the original dm-bufio, setting dm_bufio_cache_size to 0 meant to set
the default value. However, when the code was refactored in the commit
450e8dee51, the meaning of 0 is inconsistent, at some places, we just
read the variable dm_bufio_cache_size without testing it to zero.

This commit cleans up the zero handling, all reads of dm_bufio_cache_size
go through the function dm_budio_get_cache_size() and this function tests
the variable for zero and sets the default cache size in this case.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Assisted-by: Claude:claude-opus-5
This commit is contained in:
Mikulas Patocka 2026-10-12 17:56:06 +02:00
parent 005d2ec572
commit 17f7f7ef5d
1 changed files with 19 additions and 40 deletions
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59
drivers/md/dm-bufio.c
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@ -1044,12 +1044,6 @@ static unsigned long dm_bufio_default_cache_size;
*/
static unsigned long dm_bufio_cache_size;
/*
* A copy of dm_bufio_cache_size because dm_bufio_cache_size can change
* at any time. If it disagrees, the user has changed cache size.
*/
static unsigned long dm_bufio_cache_size_latch;
static DEFINE_SPINLOCK(global_spinlock);
static unsigned int dm_bufio_max_age; /* No longer does anything */
@ -1076,7 +1070,7 @@ static int dm_bufio_client_count;
static LIST_HEAD(dm_bufio_all_clients);
/*
* This mutex protects dm_bufio_cache_size_latch and dm_bufio_client_count
* This mutex protects dm_bufio_client_count
*/
static DEFINE_MUTEX(dm_bufio_clients_lock);
@ -1093,6 +1087,17 @@ static void buffer_record_stack(struct dm_buffer *b)
/*----------------------------------------------------------------*/
static unsigned long dm_budio_get_cache_size(void)
{
unsigned long s = READ_ONCE(dm_bufio_cache_size);
if (unlikely(!s)) {
unsigned long d = dm_bufio_default_cache_size;
(void)cmpxchg(&dm_bufio_cache_size, 0, d);
s = d;
}
return s;
}
static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
{
unsigned char data_mode;
@ -1120,35 +1125,13 @@ static void adjust_total_allocated(struct dm_buffer *b, bool unlink)
dm_bufio_peak_allocated = dm_bufio_current_allocated;
if (!unlink) {
if (dm_bufio_current_allocated > dm_bufio_cache_size)
if (dm_bufio_current_allocated > dm_budio_get_cache_size())
queue_work(dm_bufio_wq, &dm_bufio_replacement_work);
}
spin_unlock(&global_spinlock);
}
/*
* Change the number of clients and recalculate per-client limit.
*/
static void __cache_size_refresh(void)
{
if (WARN_ON(!mutex_is_locked(&dm_bufio_clients_lock)))
return;
if (WARN_ON(dm_bufio_client_count < 0))
return;
dm_bufio_cache_size_latch = READ_ONCE(dm_bufio_cache_size);
/*
* Use default if set to 0 and report the actual cache size used.
*/
if (!dm_bufio_cache_size_latch) {
(void)cmpxchg(&dm_bufio_cache_size, 0,
dm_bufio_default_cache_size);
dm_bufio_cache_size_latch = dm_bufio_default_cache_size;
}
}
/*
* Allocating buffer data.
*
@ -1618,7 +1601,7 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
* be allocated.
*/
while (1) {
if (dm_bufio_cache_size_latch != 1) {
if (dm_budio_get_cache_size() != 1) {
b = alloc_buffer(c, GFP_NOWAIT | __GFP_NORETRY | __GFP_NOMEMALLOC);
if (b)
return b;
@ -1627,7 +1610,7 @@ static struct dm_buffer *__alloc_buffer_wait_no_callback(struct dm_bufio_client
if (nf == NF_PREFETCH)
return NULL;
if (dm_bufio_cache_size_latch != 1 && !tried_noio_alloc) {
if (dm_budio_get_cache_size() != 1 && !tried_noio_alloc) {
dm_bufio_unlock(c);
b = alloc_buffer(c, GFP_NOIO | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
dm_bufio_lock(c);
@ -2616,7 +2599,6 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
mutex_lock(&dm_bufio_clients_lock);
dm_bufio_client_count++;
list_add(&c->client_list, &dm_bufio_all_clients);
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
return c;
@ -2658,7 +2640,6 @@ void dm_bufio_client_destroy(struct dm_bufio_client *c)
list_del(&c->client_list);
dm_bufio_client_count--;
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
@ -2827,8 +2808,8 @@ static void check_watermarks(void)
static void evict_old(void)
{
unsigned long threshold = dm_bufio_cache_size -
dm_bufio_cache_size / DM_BUFIO_LOW_WATERMARK_RATIO;
unsigned long cs = dm_budio_get_cache_size();
unsigned long threshold = cs - cs / DM_BUFIO_LOW_WATERMARK_RATIO;
int unproductive = 0;
mutex_lock(&dm_bufio_clients_lock);
@ -2889,10 +2870,8 @@ static int __init dm_bufio_init(void)
#endif
dm_bufio_default_cache_size = mem;
mutex_lock(&dm_bufio_clients_lock);
__cache_size_refresh();
mutex_unlock(&dm_bufio_clients_lock);
if (!dm_bufio_cache_size)
dm_bufio_cache_size = mem;
dm_bufio_wq = alloc_workqueue("dm_bufio_cache",
WQ_MEM_RECLAIM | WQ_PERCPU, 0);