From: Trond Myklebust <trond.myklebust@fys.uio.no>
Fix a bug in the NFS write code whereby writepage() may end up deadlocking
on clear_inode().
---
fs/nfs/write.c | 16 +++++++++++++++-
1 files changed, 15 insertions(+), 1 deletion(-)
diff -puN fs/nfs/write.c~nfs-client-deadlock-fix fs/nfs/write.c
--- 25/fs/nfs/write.c~nfs-client-deadlock-fix 2004-01-08 18:38:45.000000000 -0800
+++ 25-akpm/fs/nfs/write.c 2004-01-08 18:38:45.000000000 -0800
@@ -228,8 +228,19 @@ nfs_writepage(struct page *page, struct
unsigned long end_index;
unsigned offset = PAGE_CACHE_SIZE;
loff_t i_size = i_size_read(inode);
+ int inode_referenced = 0;
int err;
+ /*
+ * Note: We need to ensure that we have a reference to the inode
+ * if we are to do asynchronous writes. If not, waiting
+ * in nfs_wait_on_request() may deadlock with clear_inode().
+ *
+ * If igrab() fails here, then it is in any case safe to
+ * call nfs_wb_page(), since there will be no pending writes.
+ */
+ if (igrab(inode) != 0)
+ inode_referenced = 1;
end_index = i_size >> PAGE_CACHE_SHIFT;
/* Ensure we've flushed out any previous writes */
@@ -247,7 +258,8 @@ nfs_writepage(struct page *page, struct
goto out;
do_it:
lock_kernel();
- if (NFS_SERVER(inode)->wsize >= PAGE_CACHE_SIZE && !IS_SYNC(inode)) {
+ if (NFS_SERVER(inode)->wsize >= PAGE_CACHE_SIZE && !IS_SYNC(inode) &&
+ inode_referenced) {
err = nfs_writepage_async(NULL, inode, page, 0, offset);
if (err >= 0)
err = 0;
@@ -259,6 +271,8 @@ do_it:
unlock_kernel();
out:
unlock_page(page);
+ if (inode_referenced)
+ iput(inode);
return err;
}
_