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fuse: add locking to max_background and congestion_threshold changes 

Functions sequences like request_end()->flush_bg_queue() require that
max_background and congestion_threshold are constant during their
execution. Otherwise, checks like

	if (fc->num_background == fc->max_background)

made in different time may behave not like expected.

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
hifive-unleashed-5.1
Kirill Tkhai 2018-08-27 18:29:37 +03:00 committed by Miklos Szeredi
parent 2a23f2b8ad
commit 2b30a53314
1 changed files with 24 additions and 6 deletions
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30
fs/fuse/control.c
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@ -125,7 +125,12 @@ static ssize_t fuse_conn_max_background_write(struct file *file,
if (ret > 0) {
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
spin_lock(&fc->lock);
fc->max_background = val;
fc->blocked = fc->num_background >= fc->max_background;
if (!fc->blocked)
wake_up(&fc->blocked_waitq);
spin_unlock(&fc->lock);
fuse_conn_put(fc);
}
}
@ -155,18 +160,31 @@ static ssize_t fuse_conn_congestion_threshold_write(struct file *file,
size_t count, loff_t *ppos)
{
unsigned uninitialized_var(val);
struct fuse_conn *fc;
ssize_t ret;
ret = fuse_conn_limit_write(file, buf, count, ppos, &val,
max_user_congthresh);
if (ret > 0) {
struct fuse_conn *fc = fuse_ctl_file_conn_get(file);
if (fc) {
fc->congestion_threshold = val;
fuse_conn_put(fc);
if (ret <= 0)
goto out;
fc = fuse_ctl_file_conn_get(file);
if (!fc)
goto out;
spin_lock(&fc->lock);
fc->congestion_threshold = val;
if (fc->sb) {
if (fc->num_background < fc->congestion_threshold) {
clear_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
clear_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
} else {
set_bdi_congested(fc->sb->s_bdi, BLK_RW_SYNC);
set_bdi_congested(fc->sb->s_bdi, BLK_RW_ASYNC);
}
}
spin_unlock(&fc->lock);
fuse_conn_put(fc);
out:
return ret;
}