Commit 9e98e9d7 authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe

blk-mq: Avoid that __bt_get_word() wraps multiple times

If __bt_get_word() is called with last_tag != 0, if the first
find_next_zero_bit() fails, if after wrap-around the
test_and_set_bit() call fails and find_next_zero_bit() succeeds,
if the next test_and_set_bit() call fails and subsequently
find_next_zero_bit() does not find a zero bit, then another
wrap-around will occur. Avoid this by introducing an additional
local variable.
Signed-off-by: default avatarBart Van Assche <>
Cc: Christoph Hellwig <>
Cc: Robert Elliott <>
Cc: Ming Lei <>
Cc: Alexander Gordeev <>
Cc: <> # v3.13+
Signed-off-by: default avatarJens Axboe <>
parent 45a9c9d9
......@@ -137,6 +137,7 @@ static inline bool hctx_may_queue(struct blk_mq_hw_ctx *hctx,
static int __bt_get_word(struct blk_align_bitmap *bm, unsigned int last_tag)
int tag, org_last_tag, end;
bool wrap = last_tag != 0;
org_last_tag = last_tag;
end = bm->depth;
......@@ -148,8 +149,9 @@ restart:
* We started with an offset, start from 0 to
* exhaust the map.
if (org_last_tag && last_tag) {
end = last_tag;
if (wrap) {
wrap = false;
end = org_last_tag;
last_tag = 0;
goto restart;
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