From 9abca36087288fe28de4749c71ca003d4b9e3ed0 Mon Sep 17 00:00:00 2001
From: Nick Piggin <npiggin@kernel.dk>
Date: Fri, 7 Jan 2011 17:49:36 +1100
Subject: [PATCH] fs: increase d_name lock coverage
Cover d_name with d_lock in more cases, where there may be concurrent
modification to it.
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
---
fs/dcache.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index de38680ee0ed..a09f0771fd27 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -1350,6 +1350,11 @@ static struct dentry *__d_instantiate_unique(struct dentry *entry,
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct qstr *qstr = &alias->d_name;
+ /*
+ * Don't need alias->d_lock here, because aliases with
+ * d_parent == entry->d_parent are not subject to name or
+ * parent changes, because the parent inode i_mutex is held.
+ */
if (qstr->hash != hash)
continue;
if (alias->d_parent != entry->d_parent)
@@ -2313,7 +2318,9 @@ static int prepend_path(const struct path *path, struct path *root,
}
parent = dentry->d_parent;
prefetch(parent);
+ spin_lock(&dentry->d_lock);
error = prepend_name(buffer, buflen, &dentry->d_name);
+ spin_unlock(&dentry->d_lock);
if (!error)
error = prepend(buffer, buflen, "/", 1);
if (error)
@@ -2515,10 +2522,13 @@ static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
+ int error;
prefetch(parent);
- if ((prepend_name(&end, &buflen, &dentry->d_name) != 0) ||
- (prepend(&end, &buflen, "/", 1) != 0))
+ spin_lock(&dentry->d_lock);
+ error = prepend_name(&end, &buflen, &dentry->d_name);
+ spin_unlock(&dentry->d_lock);
+ if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
goto Elong;
retval = end;
--
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