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hostfs: simplify locking

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Remove dcache_lock locking from hostfs filesystem, and move it into dcache
helpers. All that is required is a coherent path name. Protection from
concurrent modification of the namespace after path name generation is not
provided in current code, because dcache_lock is dropped before the path is
used.

Signed-off-by: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:49:29 +11:00
parent b1e6a015a5
commit ec2447c278
3 changed files with 24 additions and 17 deletions
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15
fs/dcache.c
View file

@ -2171,7 +2171,7 @@ char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
/* /*
* Write full pathname from the root of the filesystem into the buffer. * 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 *end = buf + buflen;
char *retval; char *retval;
@ -2198,7 +2198,18 @@ char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
Elong: Elong:
return ERR_PTR(-ENAMETOOLONG); 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) char *dentry_path(struct dentry *dentry, char *buf, int buflen)
{ {

24
fs/hostfs/hostfs_kern.c
View file

@ -92,12 +92,10 @@ __uml_setup("hostfs=", hostfs_args,
static char *__dentry_name(struct dentry *dentry, char *name) 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; char *root;
size_t len; size_t len;
spin_unlock(&dcache_lock);
root = dentry->d_sb->s_fs_info; root = dentry->d_sb->s_fs_info;
len = strlen(root); len = strlen(root);
if (IS_ERR(p)) { if (IS_ERR(p)) {
@ -123,25 +121,23 @@ static char *dentry_name(struct dentry *dentry)
if (!name) if (!name)
return NULL; return NULL;
spin_lock(&dcache_lock);
return __dentry_name(dentry, name); /* will unlock */ return __dentry_name(dentry, name); /* will unlock */
} }
static char *inode_name(struct inode *ino) static char *inode_name(struct inode *ino)
{ {
struct dentry *dentry; struct dentry *dentry;
char *name = __getname(); char *name;
if (!name)
dentry = d_find_alias(ino);
if (!dentry)
return NULL; return NULL;
spin_lock(&dcache_lock); name = dentry_name(dentry);
if (list_empty(&ino->i_dentry)) {
spin_unlock(&dcache_lock); dput(dentry);
__putname(name);
return NULL; return name;
}
dentry = list_first_entry(&ino->i_dentry, struct dentry, d_alias);
return __dentry_name(dentry, name); /* will unlock */
} }
static char *follow_link(char *link) static char *follow_link(char *link)

2
include/linux/dcache.h
View file

@ -311,7 +311,7 @@ extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
extern char *__d_path(const struct path *path, struct path *root, char *, int); 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(const struct path *, char *, int);
extern char *d_path_with_unreachable(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); extern char *dentry_path(struct dentry *, char *, int);
/* Allocation counts.. */ /* Allocation counts.. */