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fuse: limit queued background requests 

Libfuse basically creates a new thread for each new request.  This is fine for
synchronous requests, which are naturally limited.  However background
requests (especially writepage) can cause a thread creation storm.

To avoid this, limit the number of background requests available to userspace.

This is done by introducing another queue for background requests, and a
counter for the number of "active" requests, which are currently available for
userspace.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Miklos Szeredi 2008-02-06 01:38:39 -08:00 committed by Linus Torvalds
parent b57d426445
commit d12def1bcb
3 changed files with 74 additions and 46 deletions
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101
fs/fuse/dev.c
View File

@ -201,6 +201,55 @@ void fuse_put_request(struct fuse_conn *fc, struct fuse_req *req)
}
}
static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
unsigned nbytes = 0;
unsigned i;
for (i = 0; i < numargs; i++)
nbytes += args[i].size;
return nbytes;
}
static u64 fuse_get_unique(struct fuse_conn *fc)
{
fc->reqctr++;
/* zero is special */
if (fc->reqctr == 0)
fc->reqctr = 1;
return fc->reqctr;
}
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
req->in.h.unique = fuse_get_unique(fc);
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
list_add_tail(&req->list, &fc->pending);
req->state = FUSE_REQ_PENDING;
if (!req->waiting) {
req->waiting = 1;
atomic_inc(&fc->num_waiting);
}
wake_up(&fc->waitq);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
static void flush_bg_queue(struct fuse_conn *fc)
{
while (fc->active_background < FUSE_MAX_BACKGROUND &&
!list_empty(&fc->bg_queue)) {
struct fuse_req *req;
req = list_entry(fc->bg_queue.next, struct fuse_req, list);
list_del(&req->list);
fc->active_background++;
queue_request(fc, req);
}
}
/*
* This function is called when a request is finished. Either a reply
* has arrived or it was aborted (and not yet sent) or some error
@ -229,6 +278,8 @@ static void request_end(struct fuse_conn *fc, struct fuse_req *req)
clear_bdi_congested(&fc->bdi, WRITE);
}
fc->num_background--;
fc->active_background--;
flush_bg_queue(fc);
}
spin_unlock(&fc->lock);
wake_up(&req->waitq);
@ -320,42 +371,6 @@ static void request_wait_answer(struct fuse_conn *fc, struct fuse_req *req)
}
}
static unsigned len_args(unsigned numargs, struct fuse_arg *args)
{
unsigned nbytes = 0;
unsigned i;
for (i = 0; i < numargs; i++)
nbytes += args[i].size;
return nbytes;
}
static u64 fuse_get_unique(struct fuse_conn *fc)
{
fc->reqctr++;
/* zero is special */
if (fc->reqctr == 0)
fc->reqctr = 1;
return fc->reqctr;
}
static void queue_request(struct fuse_conn *fc, struct fuse_req *req)
{
req->in.h.unique = fuse_get_unique(fc);
req->in.h.len = sizeof(struct fuse_in_header) +
len_args(req->in.numargs, (struct fuse_arg *) req->in.args);
list_add_tail(&req->list, &fc->pending);
req->state = FUSE_REQ_PENDING;
if (!req->waiting) {
req->waiting = 1;
atomic_inc(&fc->num_waiting);
}
wake_up(&fc->waitq);
kill_fasync(&fc->fasync, SIGIO, POLL_IN);
}
void request_send(struct fuse_conn *fc, struct fuse_req *req)
{
req->isreply = 1;
@ -375,10 +390,9 @@ void request_send(struct fuse_conn *fc, struct fuse_req *req)
spin_unlock(&fc->lock);
}
static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
static void request_send_nowait_locked(struct fuse_conn *fc,
struct fuse_req *req)
{
spin_lock(&fc->lock);
if (fc->connected) {
req->background = 1;
fc->num_background++;
if (fc->num_background == FUSE_MAX_BACKGROUND)
@ -387,8 +401,15 @@ static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
set_bdi_congested(&fc->bdi, READ);
set_bdi_congested(&fc->bdi, WRITE);
}
list_add_tail(&req->list, &fc->bg_queue);
flush_bg_queue(fc);
}
queue_request(fc, req);
static void request_send_nowait(struct fuse_conn *fc, struct fuse_req *req)
{
spin_lock(&fc->lock);
if (fc->connected) {
request_send_nowait_locked(fc, req);
spin_unlock(&fc->lock);
} else {
req->out.h.error = -ENOTCONN;

6
fs/fuse/fuse_i.h
View File

@ -296,6 +296,12 @@ struct fuse_conn {
/** Number of requests currently in the background */
unsigned num_background;
/** Number of background requests currently queued for userspace */
unsigned active_background;
/** The list of background requests set aside for later queuing */
struct list_head bg_queue;
/** Pending interrupts */
struct list_head interrupts;

1
fs/fuse/inode.c
View File

@ -465,6 +465,7 @@ static struct fuse_conn *new_conn(void)
INIT_LIST_HEAD(&fc->processing);
INIT_LIST_HEAD(&fc->io);
INIT_LIST_HEAD(&fc->interrupts);
INIT_LIST_HEAD(&fc->bg_queue);
atomic_set(&fc->num_waiting, 0);
fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
fc->bdi.unplug_io_fn = default_unplug_io_fn;