fs: dcache scale subdirs

Protect d_subdirs and d_child with d_lock, except in filesystems that aren't
using dcache_lock for these anyway (eg. using i_mutex).

Note: if we change the locking rule in future so that ->d_child protection is
provided only with ->d_parent->d_lock, it may allow us to reduce some locking.
But it would be an exception to an otherwise regular locking scheme, so we'd
have to see some good results. Probably not worthwhile.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/coda/cache.c b/fs/coda/cache.c
index 9060f08e70cf..859393fca2b7 100644
--- a/fs/coda/cache.c
+++ b/fs/coda/cache.c
@@ -94,6 +94,7 @@ static void coda_flag_children(struct dentry *parent, int flag)
         struct dentry *de;
 
         spin_lock(&dcache_lock);
+        spin_lock(&parent->d_lock);
         list_for_each(child, &parent->d_subdirs)
         {
                 de = list_entry(child, struct dentry, d_u.d_child);
@@ -102,6 +103,7 @@ static void coda_flag_children(struct dentry *parent, int flag)
                         continue;
                 coda_flag_inode(de->d_inode, flag);
         }
+        spin_unlock(&parent->d_lock);
         spin_unlock(&dcache_lock);
         return; 
 }