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Subject[patch 09/28] hostfs: simplify locking
Remove dcache_lock locking from hostfs filesystem, and move it into dcache
helpers. All that should really be required is a coherent path name, protection
from concurrent modification is not provided outside path name generation
because dcache_lock is dropped before the path is used.

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

---
fs/dcache.c | 15 +++++++++++++--
fs/hostfs/hostfs_kern.c | 24 ++++++++++--------------
include/linux/dcache.h | 2 +-
3 files changed, 24 insertions(+), 17 deletions(-)
Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c 2010-11-17 00:52:37.000000000 +1100
+++ linux-2.6/fs/dcache.c 2010-11-17 01:05:47.000000000 +1100
@@ -2140,7 +2140,7 @@ char *dynamic_dname(struct dentry *dentr
/*
* Write full pathname from the root of the filesystem into the buffer.
*/
-char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
+static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
{
char *end = buf + buflen;
char *retval;
@@ -2167,7 +2167,18 @@ char *__dentry_path(struct dentry *dentr
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
-EXPORT_SYMBOL(__dentry_path);
+
+char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
+{
+ char *retval;
+
+ spin_lock(&dcache_lock);
+ retval = __dentry_path(dentry, buf, buflen);
+ spin_unlock(&dcache_lock);
+
+ return retval;
+}
+EXPORT_SYMBOL(dentry_path_raw);

char *dentry_path(struct dentry *dentry, char *buf, int buflen)
{
Index: linux-2.6/fs/hostfs/hostfs_kern.c
===================================================================
--- linux-2.6.orig/fs/hostfs/hostfs_kern.c 2010-11-17 00:52:37.000000000 +1100
+++ linux-2.6/fs/hostfs/hostfs_kern.c 2010-11-17 00:52:37.000000000 +1100
@@ -92,12 +92,10 @@ __uml_setup("hostfs=", hostfs_args,

static char *__dentry_name(struct dentry *dentry, char *name)
{
- char *p = __dentry_path(dentry, name, PATH_MAX);
+ char *p = dentry_path_raw(dentry, name, PATH_MAX);
char *root;
size_t len;

- spin_unlock(&dcache_lock);
-
root = dentry->d_sb->s_fs_info;
len = strlen(root);
if (IS_ERR(p)) {
@@ -123,25 +121,23 @@ static char *dentry_name(struct dentry *
if (!name)
return NULL;

- spin_lock(&dcache_lock);
return __dentry_name(dentry, name); /* will unlock */
}

static char *inode_name(struct inode *ino)
{
struct dentry *dentry;
- char *name = __getname();
- if (!name)
- return NULL;
+ char *name;

- spin_lock(&dcache_lock);
- if (list_empty(&ino->i_dentry)) {
- spin_unlock(&dcache_lock);
- __putname(name);
+ dentry = d_find_alias(ino);
+ if (!dentry)
return NULL;
- }
- dentry = list_first_entry(&ino->i_dentry, struct dentry, d_alias);
- return __dentry_name(dentry, name); /* will unlock */
+
+ name = dentry_name(dentry);
+
+ dput(dentry);
+
+ return name;
}

static char *follow_link(char *link)
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h 2010-11-17 00:52:37.000000000 +1100
+++ linux-2.6/include/linux/dcache.h 2010-11-17 01:05:47.000000000 +1100
@@ -309,7 +309,7 @@ extern char *dynamic_dname(struct dentry
extern char *__d_path(const struct path *path, struct path *root, char *, int);
extern char *d_path(const struct path *, char *, int);
extern char *d_path_with_unreachable(const struct path *, char *, int);
-extern char *__dentry_path(struct dentry *, char *, int);
+extern char *dentry_path_raw(struct dentry *, char *, int);
extern char *dentry_path(struct dentry *, char *, int);

/* Allocation counts.. */



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