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Subject[PATCH 4/4] SUNRPC: move cache_detail->cache_request callback call to cache_read()
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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>
---
net/sunrpc/cache.c | 32 ++++++++++++++++++++------------
1 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/net/sunrpc/cache.c b/net/sunrpc/cache.c
index 901fdca..55f044c 100644
--- a/net/sunrpc/cache.c
+++ b/net/sunrpc/cache.c
@@ -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 (!cache_listeners_exist(detail)) {
warn_no_listener(detail);
@@ -1163,19 +1180,10 @@ 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);


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