diff options
author | Paul Clements <paul.clements@steeleye.com> | 2004-08-22 23:03:50 -0700 |
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committer | Linus Torvalds <torvalds@ppc970.osdl.org> | 2004-08-22 23:03:50 -0700 |
commit | bc7e55089923f130eefe2955f1e150350a450933 (patch) | |
tree | 1848e7f29199c7483490821b2e7df00f0bb28707 /drivers | |
parent | 5a3d730ca9e9d61a5ad4f8c4faa2655fce41cbda (diff) | |
download | history-bc7e55089923f130eefe2955f1e150350a450933.tar.gz |
[PATCH] nbd: fix struct request race condition
Here's a patch to fix a race condition in nbd that was causing struct
request corruption (requests were being freed while still in use). This
patch improves on the previous one, which admittedly was a bit dodgy, using
struct request's ref_count field (I should have listened to Jens in the
first place :). This should fix all the corner cases related to struct
request usage/freeing in nbd. My stress tests do a lot better with this
patch applied.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'drivers')
-rw-r--r-- | drivers/block/nbd.c | 39 |
1 files changed, 10 insertions, 29 deletions
diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index b98b70b8fdb991..75ad39dc653d64 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -128,23 +128,11 @@ static void nbd_end_request(struct request *req) { int uptodate = (req->errors == 0) ? 1 : 0; request_queue_t *q = req->q; - struct nbd_device *lo = req->rq_disk->private_data; unsigned long flags; dprintk(DBG_BLKDEV, "%s: request %p: %s\n", req->rq_disk->disk_name, req, uptodate? "done": "failed"); - spin_lock(&lo->queue_lock); - while (req->ref_count > 1) { /* still in send */ - spin_unlock(&lo->queue_lock); - printk(KERN_DEBUG "%s: request %p still in use (%d), waiting\n", - lo->disk->disk_name, req, req->ref_count); - set_current_state(TASK_UNINTERRUPTIBLE); - schedule_timeout(HZ); /* wait a second */ - spin_lock(&lo->queue_lock); - } - spin_unlock(&lo->queue_lock); - spin_lock_irqsave(q->queue_lock, flags); if (!end_that_request_first(req, uptodate, req->nr_sectors)) { end_that_request_last(req); @@ -228,7 +216,7 @@ static inline int sock_send_bvec(struct socket *sock, struct bio_vec *bvec, return result; } -void nbd_send_req(struct nbd_device *lo, struct request *req) +static int nbd_send_req(struct nbd_device *lo, struct request *req) { int result, i, flags; struct nbd_request request; @@ -288,11 +276,11 @@ void nbd_send_req(struct nbd_device *lo, struct request *req) } } up(&lo->tx_lock); - return; + return 0; error_out: up(&lo->tx_lock); - req->errors++; + return 1; } static struct request *nbd_find_request(struct nbd_device *lo, char *handle) @@ -477,26 +465,19 @@ static void do_nbd_request(request_queue_t * q) } list_add(&req->queuelist, &lo->queue_head); - req->ref_count++; /* make sure req does not get freed */ spin_unlock(&lo->queue_lock); - nbd_send_req(lo, req); - - if (req->errors) { + if (nbd_send_req(lo, req) != 0) { printk(KERN_ERR "%s: Request send failed\n", lo->disk->disk_name); - spin_lock(&lo->queue_lock); - list_del_init(&req->queuelist); - req->ref_count--; - spin_unlock(&lo->queue_lock); - nbd_end_request(req); - spin_lock_irq(q->queue_lock); - continue; + if (nbd_find_request(lo, (char *)&req) != NULL) { + /* we still own req */ + req->errors++; + nbd_end_request(req); + } else /* we're racing with nbd_clear_que */ + printk(KERN_DEBUG "nbd: can't find req\n"); } - spin_lock(&lo->queue_lock); - req->ref_count--; - spin_unlock(&lo->queue_lock); spin_lock_irq(q->queue_lock); continue; |