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Subject[patch 2/3] dentry->d_count fixes



- nfs_unlink() can race with lockless d_lookup() as d_lookup() can
successfully lookup a dentry for which nfs_unlink() can assume that no one
else is using and can go ahead and do nfs_safe_remove() on it. By using
per dentry lock, it is solved as we d_lookup() will fail the lookup for
unhashed dentries.


fs/nfs/dir.c | 3 +++
1 files changed, 3 insertions(+)

diff -puN fs/nfs/dir.c~nfs_unlink-d_count-fix fs/nfs/dir.c
--- linux-2.5.72-mm2/fs/nfs/dir.c~nfs_unlink-d_count-fix 2003-06-19 17:38:51.000000000 +0530
+++ linux-2.5.72-mm2-maneesh/fs/nfs/dir.c 2003-06-19 17:38:56.000000000 +0530
@@ -1015,7 +1015,9 @@ static int nfs_unlink(struct inode *dir,

lock_kernel();
spin_lock(&dcache_lock);
+ spin_lock(&dentry->d_lock);
if (atomic_read(&dentry->d_count) > 1) {
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
error = nfs_sillyrename(dir, dentry);
unlock_kernel();
@@ -1025,6 +1027,7 @@ static int nfs_unlink(struct inode *dir,
__d_drop(dentry);
need_rehash = 1;
}
+ spin_unlock(&dentry->d_lock);
spin_unlock(&dcache_lock);
error = nfs_safe_remove(dentry);
if (!error)
_
--
Maneesh Soni
IBM Linux Technology Center,
IBM India Software Lab, Bangalore.
Phone: +91-80-5044999 email: maneesh@in.ibm.com
http://lse.sourceforge.net/
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