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Subject[PATCH 4/5] NFS: Fix race in nfs_set_page_dirty
Date
From: Trond Myklebust <Trond.Myklebust@netapp.com>

Protect nfs_set_page_dirty() against races with nfs_inode_add_request.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
---
fs/nfs/write.c | 17 ++++++++++++++---
1 files changed, 14 insertions(+), 3 deletions(-)
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index ce5b4a9..7975589 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -388,6 +388,8 @@ static int nfs_inode_add_request(struct inode *inode, struct nfs_page *req)
}
SetPagePrivate(req->wb_page);
set_page_private(req->wb_page, (unsigned long)req);
+ if (PageDirty(req->wb_page))
+ set_bit(PG_NEED_FLUSH, &req->wb_flags);
nfsi->npages++;
atomic_inc(&req->wb_count);
return 0;
@@ -407,6 +409,8 @@ static void nfs_inode_remove_request(struct nfs_page *req)
set_page_private(req->wb_page, 0);
ClearPagePrivate(req->wb_page);
radix_tree_delete(&nfsi->nfs_page_tree, req->wb_index);
+ if (test_and_clear_bit(PG_NEED_FLUSH, &req->wb_flags))
+ __set_page_dirty_nobuffers(req->wb_page);
nfsi->npages--;
if (!nfsi->npages) {
spin_unlock(&nfsi->req_lock);
@@ -1527,15 +1531,22 @@ int nfs_wb_page(struct inode *inode, struct page* page)

int nfs_set_page_dirty(struct page *page)
{
+ spinlock_t *req_lock = &NFS_I(page->mapping->host)->req_lock;
struct nfs_page *req;
+ int ret;

- req = nfs_page_find_request(page);
+ spin_lock(req_lock);
+ req = nfs_page_find_request_locked(page);
if (req != NULL) {
/* Mark any existing write requests for flushing */
- set_bit(PG_NEED_FLUSH, &req->wb_flags);
+ ret = !test_and_set_bit(PG_NEED_FLUSH, &req->wb_flags);
+ spin_unlock(req_lock);
nfs_release_request(req);
+ return ret;
}
- return __set_page_dirty_nobuffers(page);
+ ret = __set_page_dirty_nobuffers(page);
+ spin_unlock(req_lock);
+ return ret;
}


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