maillist inclusion category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IA8D5J

Reference: https://lore.kernel.org/r/20240604030522.3686177-1-libaokun@huaweicloud.com/

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Now we avoid throttling swap writes by determining whether the current process is kswapd (aka current_is_kswapd()), but swap writes can come from either kswapd or direct reclaim, so the swap writes from direct reclaim will still be throttled.

When a process holds a lock to allocate a free page, and enters direct reclaim because there is no free memory, then it might trigger a hung due to the wbt throttling that causes other processes to fail to get the lock.

Both kswapd and direct reclaim set the REQ_SWAP flag, so use REQ_SWAP instead of current_is_kswapd() to avoid throttling swap writes. Also renamed WBT_KSWAPD to WBT_SWAP and WBT_RWQ_KSWAPD to WBT_RWQ_SWAP.

Signed-off-by: Baokun Li libaokun1@huawei.com Reviewed-by: Yu Kuai yukuai3@huawei.com Signed-off-by: Baokun Li libaokun1@huawei.com --- block/blk-wbt.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/block/blk-wbt.c b/block/blk-wbt.c index f8fda9cf583e..296cdfea7c2a 100644 --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -36,7 +36,7 @@ enum wbt_flags { WBT_TRACKED = 1, /* write, tracked for throttling */ WBT_READ = 2, /* read */ - WBT_KSWAPD = 4, /* write, from kswapd */ + WBT_SWAP = 4, /* write, from swap_writepage() */ WBT_DISCARD = 8, /* discard */

WBT_NR_BITS = 4, /* number of bits */ @@ -44,7 +44,7 @@ enum wbt_flags {

enum { WBT_RWQ_BG = 0, - WBT_RWQ_KSWAPD, + WBT_RWQ_SWAP, WBT_RWQ_DISCARD, WBT_NUM_RWQ, }; @@ -173,8 +173,8 @@ static bool wb_recent_wait(struct rq_wb *rwb) static inline struct rq_wait *get_rq_wait(struct rq_wb *rwb, enum wbt_flags wb_acct) { - if (wb_acct & WBT_KSWAPD) - return &rwb->rq_wait[WBT_RWQ_KSWAPD]; + if (wb_acct & WBT_SWAP) + return &rwb->rq_wait[WBT_RWQ_SWAP]; else if (wb_acct & WBT_DISCARD) return &rwb->rq_wait[WBT_RWQ_DISCARD];

@@ -529,7 +529,7 @@ static bool close_io(struct rq_wb *rwb) time_before(now, rwb->last_comp + HZ / 10); }

-#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO) +#define REQ_HIPRIO (REQ_SYNC | REQ_META | REQ_PRIO | REQ_SWAP)

static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf) { @@ -540,13 +540,13 @@ static inline unsigned int get_limit(struct rq_wb *rwb, blk_opf_t opf)

/* * At this point we know it's a buffered write. If this is - * kswapd trying to free memory, or REQ_SYNC is set, then + * swap trying to free memory, or REQ_SYNC is set, then * it's WB_SYNC_ALL writeback, and we'll use the max limit for * that. If the write is marked as a background write, then use * the idle limit, or go to normal if we haven't had competing * IO for a bit. */ - if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd()) + if ((opf & REQ_HIPRIO) || wb_recent_wait(rwb)) limit = rwb->rq_depth.max_depth; else if ((opf & REQ_BACKGROUND) || close_io(rwb)) { /* @@ -623,8 +623,8 @@ static enum wbt_flags bio_to_wbt_flags(struct rq_wb *rwb, struct bio *bio) if (bio_op(bio) == REQ_OP_READ) { flags = WBT_READ; } else if (wbt_should_throttle(bio)) { - if (current_is_kswapd()) - flags |= WBT_KSWAPD; + if (bio->bi_opf & REQ_SWAP) + flags |= WBT_SWAP; if (bio_op(bio) == REQ_OP_DISCARD) flags |= WBT_DISCARD; flags |= WBT_TRACKED;