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authorTrond Myklebust <Trond.Myklebust@netapp.com>2012-05-09 14:30:35 -0400
committerTrond Myklebust <Trond.Myklebust@netapp.com>2012-05-09 15:16:07 -0400
commit3aff4ebb95b20ad8db2c1447e8c52097d89af5a7 (patch)
treead56aceafbcbd0650e71e029ffa138eedffd33ba /fs/nfs/pagelist.c
parentdc327ed4cd320be689596365372a3683208c3ba0 (diff)
NFS: Prevent a deadlock in the new writeback code
We have to unlock the nfs_page before we call nfs_end_page_writeback to avoid races with functions that expect the page to be unlocked when PG_locked and PG_writeback are not set. The problem is that nfs_unlock_request also releases the nfs_page, causing a deadlock if the release of the nfs_open_context triggers an iput() while the PG_writeback flag is still set... The solution is to separate the unlocking and release of the nfs_page, so that we can do the former before nfs_end_page_writeback and the latter after. Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Cc: Fred Isaman <iisaman@netapp.com>
Diffstat (limited to 'fs/nfs/pagelist.c')
-rw-r--r--fs/nfs/pagelist.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 33a21ca9b84b..69146f386989 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -128,10 +128,10 @@ nfs_create_request(struct nfs_open_context *ctx, struct inode *inode,
}
/**
- * nfs_unlock_request - Unlock request and wake up sleepers.
+ * nfs_unlock_request_dont_release - Unlock request and wake up sleepers.
* @req:
*/
-void nfs_unlock_request(struct nfs_page *req)
+void nfs_unlock_request_dont_release(struct nfs_page *req)
{
if (!NFS_WBACK_BUSY(req)) {
printk(KERN_ERR "NFS: Invalid unlock attempted\n");
@@ -141,6 +141,14 @@ void nfs_unlock_request(struct nfs_page *req)
clear_bit(PG_BUSY, &req->wb_flags);
smp_mb__after_clear_bit();
wake_up_bit(&req->wb_flags, PG_BUSY);
+}
+
+/**
+ * nfs_unlock_request - Unlock request and release the nfs_page
+ */
+void nfs_unlock_request(struct nfs_page *req)
+{
+ nfs_unlock_request_dont_release(req);
nfs_release_request(req);
}