The patch b32d45824aa7 ("dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag")
added a "NO_SLEEP" mode, it replaces a mutex with a spinlock, and it is
only usable when the device is in read-only mode (because the write path
may be sleeping while holding the dm_bufio_client lock).
However, there are still two points where the code could sleep even in
read-only mode. One is in __get_unclaimed_buffer -> __make_buffer_clean.
The other is in __try_evict_buffer -> __make_buffer_clean. These functions
will call __make_buffer_clean which sleeps if the buffer is being read.
This patch fixes these cases, so that if c->no_sleep is set, we won't call
__make_buffer_clean and we skip the buffer instead.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Fixes: b32d45824aa7 ("dm bufio: Add DM_BUFIO_CLIENT_NO_SLEEP flag")
Index: linux-2.6/drivers/md/dm-bufio.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-bufio.c
+++ linux-2.6/drivers/md/dm-bufio.c
@@ -817,6 +817,9 @@ static struct dm_buffer *__get_unclaimed
BUG_ON(test_bit(B_WRITING, &b->state));
BUG_ON(test_bit(B_DIRTY, &b->state));
+ if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep && unlikely(test_bit(B_READING, &b->state)))
+ continue;
+
if (!b->hold_count) {
__make_buffer_clean(b);
__unlink_buffer(b);
@@ -825,6 +828,9 @@ static struct dm_buffer *__get_unclaimed
cond_resched();
}
+ if (static_branch_unlikely(&no_sleep_enabled) && c->no_sleep)
+ return NULL;
+
list_for_each_entry_reverse(b, &c->lru[LIST_DIRTY], lru_list) {
BUG_ON(test_bit(B_READING, &b->state));
@@ -1632,7 +1638,7 @@ static void drop_buffers(struct dm_bufio
*/
static bool __try_evict_buffer(struct dm_buffer *b, gfp_t gfp)
{
- if (!(gfp & __GFP_FS)) {
+ if (!(gfp & __GFP_FS) || (static_branch_unlikely(&no_sleep_enabled) && b->c->no_sleep)) {
if (test_bit(B_READING, &b->state) ||
test_bit(B_WRITING, &b->state) ||
test_bit(B_DIRTY, &b->state))
--
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