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SUNRPC: move cache_detail->cache_request callback call to cache_read() 

The reason to move cache_request() callback call from
sunrpc_cache_pipe_upcall() to cache_read() is that this garantees, that cache
access will be done userspace process context (only userspace process have
proper root context).
This is required for NFSd support in container: svc_export_request() (which is
cache_request callback) calls d_path(), which, in turn, traverse dentry up to
current->fs->root. Kernel threads always have global root, while container
have be in "root jail" - i.e. have it's own nested root.

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
This commit is contained in:
Stanislav Kinsbursky 2013-02-04 14:03:03 +03:00 committed by J. Bruce Fields
parent 21cd1254d3
commit d94af6dea9
1 changed files with 20 additions and 12 deletions
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32
net/sunrpc/cache.c
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@ -750,6 +750,18 @@ struct cache_reader {
int offset; /* if non-0, we have a refcnt on next request */
};
static int cache_request(struct cache_detail *detail,
struct cache_request *crq)
{
char *bp = crq->buf;
int len = PAGE_SIZE;
detail->cache_request(detail, crq->item, &bp, &len);
if (len < 0)
return -EAGAIN;
return PAGE_SIZE - len;
}
static ssize_t cache_read(struct file *filp, char __user *buf, size_t count,
loff_t *ppos, struct cache_detail *cd)
{
@ -784,6 +796,13 @@ static ssize_t cache_read(struct file *filp, char __user *buf, size_t count,
rq->readers++;
spin_unlock(&queue_lock);
if (rq->len == 0) {
err = cache_request(cd, rq);
if (err < 0)
goto out;
rq->len = err;
}
if (rp->offset == 0 && !test_bit(CACHE_PENDING, &rq->item->flags)) {
err = -EAGAIN;
spin_lock(&queue_lock);
@ -1145,8 +1164,6 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
char *buf;
struct cache_request *crq;
char *bp;
int len;
if (!detail->cache_request)
return -EINVAL;
@ -1166,19 +1183,10 @@ int sunrpc_cache_pipe_upcall(struct cache_detail *detail, struct cache_head *h)
return -EAGAIN;
}
bp = buf; len = PAGE_SIZE;
detail->cache_request(detail, h, &bp, &len);
if (len < 0) {
kfree(buf);
kfree(crq);
return -EAGAIN;
}
crq->q.reader = 0;
crq->item = cache_get(h);
crq->buf = buf;
crq->len = PAGE_SIZE - len;
crq->len = 0;
crq->readers = 0;
spin_lock(&queue_lock);
list_add_tail(&crq->q.list, &detail->queue);