From: Baokun Li libaokun1@huawei.com
mainline inclusion from mainline-v6.11-rc1 commit 4e63aeb5d0101ddada36a2f64f048e2f9d2202fc category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/IA8D5J CVE: NA
Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i...
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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 Reviewed-by: Christoph Hellwig hch@lst.de Link: https://lore.kernel.org/r/20240604030522.3686177-1-libaokun@huaweicloud.com Signed-off-by: Jens Axboe axboe@kernel.dk
Conflicts: block/blk-wbt.c [commit 16458cf3bd15 ("block: Use the new blk_opf_t type") is not backported] Signed-off-by: Yu Kuai yukuai3@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 799caf8e4dcb..183f26a83347 100644 --- a/block/blk-wbt.c +++ b/block/blk-wbt.c @@ -35,7 +35,7 @@ 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 */ @@ -43,7 +43,7 @@ enum wbt_flags {
enum { WBT_RWQ_BG = 0, - WBT_RWQ_KSWAPD, + WBT_RWQ_SWAP, WBT_RWQ_DISCARD, WBT_NUM_RWQ, }; @@ -172,8 +172,8 @@ 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];
@@ -536,7 +536,7 @@ 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, unsigned long rw) { @@ -554,13 +554,13 @@ static inline unsigned int get_limit(struct rq_wb *rwb, unsigned long rw)
/* * 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 ((rw & REQ_HIPRIO) || wb_recent_wait(rwb) || current_is_kswapd()) + if ((rw & REQ_HIPRIO) || wb_recent_wait(rwb)) limit = rwb->rq_depth.max_depth; else if ((rw & REQ_BACKGROUND) || close_io(rwb)) { /* @@ -637,8 +637,8 @@ 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(rwb, 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;