On Tue, 2010-12-07 at 22:17 -0500, Trond Myklebust wrote:
> OK... I think I see why the hang:
>
> I believe that it is basically due to nfs_clear_page_tag_locked() making
> the assumption that if req->wb_page != NULL, then the corresponding
> nfsi->nfs_page_tree lock tag needs to be cleared.
>
> Maybe we can do that differently by just setting a flag to indicate
> whether or not this request is mapped into the radix tree...
The following patch is completely untested, but should do the trick....
----------------------------------------------------------------------------------------
>From e0e77c1988ec09a8107950e7e949c5395a272e20 Mon Sep 17 00:00:00 2001
From: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Date: Tue, 7 Dec 2010 22:39:17 -0500
Subject: [PATCH] nfs: remove extraneous and problematic calls to nfs_clear_request
When a nfs_page is freed, nfs_free_request is called which also calls
nfs_clear_request to clean out the lock and open contexts and free the
pagecache page.
However, a couple of places in the nfs code call nfs_clear_request
themselves. What happens here if the refcount on the request is still high?
We'll be releasing contexts and freeing pointers while the request is
possibly still in use.
Remove those bare calls to nfs_clear_context. That should only be done when
the request is being freed.
Note that when doing this, we need to watch out for tests of req->wb_page.
Previously, nfs_set_page_tag_locked() and nfs_clear_page_tag_locked()
check the value of req->wb_page to figure out if the page is mapped
into the nfsi->nfs_page_tree. We now indicate the page is mapped using
the new bit PG_MAPPED in req->wb_flags .
Reported-by: Jeff Layton <jlayton@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
---
fs/nfs/pagelist.c | 4 ++--
fs/nfs/read.c | 1 -
fs/nfs/write.c | 3 ++-
include/linux/nfs_page.h | 1 +
4 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 137b549..b68536c 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -115,7 +115,7 @@ int nfs_set_page_tag_locked(struct nfs_page *req)
{
if (!nfs_lock_request_dontget(req))
return 0;
- if (req->wb_page != NULL)
+ if (test_bit(PG_MAPPED, &req->wb_flags))
radix_tree_tag_set(&NFS_I(req->wb_context->path.dentry->d_inode)->nfs_page_tree, req->wb_index, NFS_PAGE_TAG_LOCKED);
return 1;
}
@@ -125,7 +125,7 @@ int nfs_set_page_tag_locked(struct nfs_page *req)
*/
void nfs_clear_page_tag_locked(struct nfs_page *req)
{
- if (req->wb_page != NULL) {
+ if (test_bit(PG_MAPPED, &req->wb_flags)) {
struct inode *inode = req->wb_context->path.dentry->d_inode;
struct nfs_inode *nfsi = NFS_I(inode);
diff --git a/fs/nfs/read.c b/fs/nfs/read.c
index e4b62c6..aedcaa7 100644
--- a/fs/nfs/read.c
+++ b/fs/nfs/read.c
@@ -152,7 +152,6 @@ static void nfs_readpage_release(struct nfs_page *req)
(long long)NFS_FILEID(req->wb_context->path.dentry->d_inode),
req->wb_bytes,
(long long)req_offset(req));
- nfs_clear_request(req);
nfs_release_request(req);
}
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 4c14c17..10d648e 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -390,6 +390,7 @@ static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
if (nfs_have_delegation(inode, FMODE_WRITE))
nfsi->change_attr++;
}
+ set_bit(PG_MAPPED, &req->wb_flags);
SetPagePrivate(req->wb_page);
set_page_private(req->wb_page, (unsigned long)req);
nfsi->npages++;
@@ -415,6 +416,7 @@ static void nfs_inode_remove_request(struct nfs_page *req)
spin_lock(&inode->i_lock);
set_page_private(req->wb_page, 0);
ClearPagePrivate(req->wb_page);
+ clear_bit(PG_MAPPED, &req->wb_flags);
radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
nfsi->npages--;
if (!nfsi->npages) {
@@ -422,7 +424,6 @@ static void nfs_inode_remove_request(struct nfs_page *req)
iput(inode);
} else
spin_unlock(&inode->i_lock);
- nfs_clear_request(req);
nfs_release_request(req);
}
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index f8b60e7..d55cee7 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -29,6 +29,7 @@
*/
enum {
PG_BUSY = 0,
+ PG_MAPPED,
PG_CLEAN,
PG_NEED_COMMIT,
PG_NEED_RESCHED,
--
1.7.3.2
--
Trond Myklebust
Linux NFS client maintainer
NetApp
Trond.Myklebust@xxxxxxxxxx
www.netapp.com
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