From: Jeff Layton Date: Mon, 23 Feb 2026 17:10:01 +0000 (-0500) Subject: sunrpc: split cache_detail queue into request and reader lists X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=facc4e3c80420e3466003ce09b576e005b56a015;p=thirdparty%2Flinux.git sunrpc: split cache_detail queue into request and reader lists Replace the single interleaved queue (which mixed cache_request and cache_reader entries distinguished by a ->reader flag) with two dedicated lists: cd->requests for upcall requests and cd->readers for open file handles. Readers now track their position via a monotonically increasing sequence number (next_seqno) rather than by their position in the shared list. Each cache_request is assigned a seqno when enqueued, and a new cache_next_request() helper finds the next request at or after a given seqno. This eliminates the cache_queue wrapper struct entirely, simplifies the reader-skipping loops in cache_read/cache_poll/cache_ioctl/ cache_release, and makes the data flow easier to reason about. Signed-off-by: Jeff Layton Signed-off-by: Chuck Lever --- diff --git a/include/linux/sunrpc/cache.h b/include/linux/sunrpc/cache.h index 031379efba24..b1e595c2615b 100644 --- a/include/linux/sunrpc/cache.h +++ b/include/linux/sunrpc/cache.h @@ -113,9 +113,11 @@ struct cache_detail { int entries; /* fields for communication over channel */ - struct list_head queue; + struct list_head requests; + struct list_head readers; spinlock_t queue_lock; wait_queue_head_t queue_wait; + u64 next_seqno; atomic_t writers; /* how many time is /channel open */ time64_t last_close; /* if no writers, when did last close */ diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c index fd02dca1f07a..7081c1214e6c 100644 --- a/net/sunrpc/cache.c +++ b/net/sunrpc/cache.c @@ -399,9 +399,11 @@ static struct delayed_work cache_cleaner; void sunrpc_init_cache_detail(struct cache_detail *cd) { spin_lock_init(&cd->hash_lock); - INIT_LIST_HEAD(&cd->queue); + INIT_LIST_HEAD(&cd->requests); + INIT_LIST_HEAD(&cd->readers); spin_lock_init(&cd->queue_lock); init_waitqueue_head(&cd->queue_wait); + cd->next_seqno = 0; spin_lock(&cache_list_lock); cd->nextcheck = 0; cd->entries = 0; @@ -796,29 +798,20 @@ void cache_clean_deferred(void *owner) * On read, you get a full request, or block. * On write, an update request is processed. * Poll works if anything to read, and always allows write. - * - * Implemented by linked list of requests. Each open file has - * a ->private that also exists in this list. New requests are added - * to the end and may wakeup and preceding readers. - * New readers are added to the head. If, on read, an item is found with - * CACHE_UPCALLING clear, we free it from the list. - * */ -struct cache_queue { - struct list_head list; - int reader; /* if 0, then request */ -}; struct cache_request { - struct cache_queue q; + struct list_head list; struct cache_head *item; - char * buf; + char *buf; int len; int readers; + u64 seqno; }; struct cache_reader { - struct cache_queue q; + struct list_head list; int offset; /* if non-0, we have a refcnt on next request */ + u64 next_seqno; }; static int cache_request(struct cache_detail *detail, @@ -833,6 +826,17 @@ static int cache_request(struct cache_detail *detail, return PAGE_SIZE - len; } +static struct cache_request * +cache_next_request(struct cache_detail *cd, u64 seqno) +{ + struct cache_request *rq; + + list_for_each_entry(rq, &cd->requests, list) + if (rq->seqno >= seqno) + return rq; + return NULL; +} + static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos, struct cache_detail *cd) { @@ -849,20 +853,13 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, again: spin_lock(&cd->queue_lock); /* need to find next request */ - while (rp->q.list.next != &cd->queue && - list_entry(rp->q.list.next, struct cache_queue, list) - ->reader) { - struct list_head *next = rp->q.list.next; - list_move(&rp->q.list, next); - } - if (rp->q.list.next == &cd->queue) { + rq = cache_next_request(cd, rp->next_seqno); + if (!rq) { spin_unlock(&cd->queue_lock); inode_unlock(inode); WARN_ON_ONCE(rp->offset); return 0; } - rq = container_of(rp->q.list.next, struct cache_request, q.list); - WARN_ON_ONCE(rq->q.reader); if (rp->offset == 0) rq->readers++; spin_unlock(&cd->queue_lock); @@ -876,9 +873,7 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) { err = -EAGAIN; - spin_lock(&cd->queue_lock); - list_move(&rp->q.list, &rq->q.list); - spin_unlock(&cd->queue_lock); + rp->next_seqno = rq->seqno + 1; } else { if (rp->offset + count > rq->len) count = rq->len - rp->offset; @@ -888,9 +883,7 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, rp->offset += count; if (rp->offset >= rq->len) { rp->offset = 0; - spin_lock(&cd->queue_lock); - list_move(&rp->q.list, &rq->q.list); - spin_unlock(&cd->queue_lock); + rp->next_seqno = rq->seqno + 1; } err = 0; } @@ -901,7 +894,7 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count, rq->readers--; if (rq->readers == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) { - list_del(&rq->q.list); + list_del(&rq->list); spin_unlock(&cd->queue_lock); cache_put(rq->item, cd); kfree(rq->buf); @@ -976,7 +969,6 @@ static __poll_t cache_poll(struct file *filp, poll_table *wait, { __poll_t mask; struct cache_reader *rp = filp->private_data; - struct cache_queue *cq; poll_wait(filp, &cd->queue_wait, wait); @@ -988,12 +980,8 @@ static __poll_t cache_poll(struct file *filp, poll_table *wait, spin_lock(&cd->queue_lock); - for (cq= &rp->q; &cq->list != &cd->queue; - cq = list_entry(cq->list.next, struct cache_queue, list)) - if (!cq->reader) { - mask |= EPOLLIN | EPOLLRDNORM; - break; - } + if (cache_next_request(cd, rp->next_seqno)) + mask |= EPOLLIN | EPOLLRDNORM; spin_unlock(&cd->queue_lock); return mask; } @@ -1004,7 +992,7 @@ static int cache_ioctl(struct inode *ino, struct file *filp, { int len = 0; struct cache_reader *rp = filp->private_data; - struct cache_queue *cq; + struct cache_request *rq; if (cmd != FIONREAD || !rp) return -EINVAL; @@ -1014,14 +1002,9 @@ static int cache_ioctl(struct inode *ino, struct file *filp, /* only find the length remaining in current request, * or the length of the next request */ - for (cq= &rp->q; &cq->list != &cd->queue; - cq = list_entry(cq->list.next, struct cache_queue, list)) - if (!cq->reader) { - struct cache_request *cr = - container_of(cq, struct cache_request, q); - len = cr->len - rp->offset; - break; - } + rq = cache_next_request(cd, rp->next_seqno); + if (rq) + len = rq->len - rp->offset; spin_unlock(&cd->queue_lock); return put_user(len, (int __user *)arg); @@ -1042,10 +1025,10 @@ static int cache_open(struct inode *inode, struct file *filp, return -ENOMEM; } rp->offset = 0; - rp->q.reader = 1; + rp->next_seqno = 0; spin_lock(&cd->queue_lock); - list_add(&rp->q.list, &cd->queue); + list_add(&rp->list, &cd->readers); spin_unlock(&cd->queue_lock); } if (filp->f_mode & FMODE_WRITE) @@ -1064,26 +1047,21 @@ static int cache_release(struct inode *inode, struct file *filp, spin_lock(&cd->queue_lock); if (rp->offset) { - struct cache_queue *cq; - for (cq = &rp->q; &cq->list != &cd->queue; - cq = list_entry(cq->list.next, - struct cache_queue, list)) - if (!cq->reader) { - struct cache_request *cr = - container_of(cq, - struct cache_request, q); - cr->readers--; - if (cr->readers == 0 && - !test_bit(CACHE_PENDING, - &cr->item->flags)) { - list_del(&cr->q.list); - rq = cr; - } - break; + struct cache_request *cr; + + cr = cache_next_request(cd, rp->next_seqno); + if (cr) { + cr->readers--; + if (cr->readers == 0 && + !test_bit(CACHE_PENDING, + &cr->item->flags)) { + list_del(&cr->list); + rq = cr; } + } rp->offset = 0; } - list_del(&rp->q.list); + list_del(&rp->list); spin_unlock(&cd->queue_lock); if (rq) { @@ -1107,27 +1085,24 @@ static int cache_release(struct inode *inode, struct file *filp, static void cache_dequeue(struct cache_detail *detail, struct cache_head *ch) { - struct cache_queue *cq, *tmp; - struct cache_request *cr; + struct cache_request *cr, *tmp; LIST_HEAD(dequeued); spin_lock(&detail->queue_lock); - list_for_each_entry_safe(cq, tmp, &detail->queue, list) - if (!cq->reader) { - cr = container_of(cq, struct cache_request, q); - if (cr->item != ch) - continue; - if (test_bit(CACHE_PENDING, &ch->flags)) - /* Lost a race and it is pending again */ - break; - if (cr->readers != 0) - continue; - list_move(&cr->q.list, &dequeued); - } + list_for_each_entry_safe(cr, tmp, &detail->requests, list) { + if (cr->item != ch) + continue; + if (test_bit(CACHE_PENDING, &ch->flags)) + /* Lost a race and it is pending again */ + break; + if (cr->readers != 0) + continue; + list_move(&cr->list, &dequeued); + } spin_unlock(&detail->queue_lock); while (!list_empty(&dequeued)) { - cr = list_entry(dequeued.next, struct cache_request, q.list); - list_del(&cr->q.list); + cr = list_entry(dequeued.next, struct cache_request, list); + list_del(&cr->list); cache_put(cr->item, detail); kfree(cr->buf); kfree(cr); @@ -1245,14 +1220,14 @@ static int cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h) return -EAGAIN; } - crq->q.reader = 0; crq->buf = buf; crq->len = 0; crq->readers = 0; spin_lock(&detail->queue_lock); if (test_bit(CACHE_PENDING, &h->flags)) { crq->item = cache_get(h); - list_add_tail(&crq->q.list, &detail->queue); + crq->seqno = detail->next_seqno++; + list_add_tail(&crq->list, &detail->requests); trace_cache_entry_upcall(detail, h); } else /* Lost a race, no longer PENDING, so don't enqueue */