fs: change d_compare for rcu-walk

Change d_compare so it may be called from lock-free RCU lookups. This
does put significant restrictions on what may be done from the callback,
however there don't seem to have been any problems with in-tree fses.
If some strange use case pops up that _really_ cannot cope with the
rcu-walk rules, we can just add new rcu-unaware callbacks, which would
cause name lookup to drop out of rcu-walk mode.

For in-tree filesystems, this is just a mechanical change.

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

2 files changed, 49 insertions, 46 deletions

diff --git a/fs/isofs/inode.c b/fs/isofs/inode.c
index bfdeb82a53be..7b0fbc61af81 100644
--- a/fs/isofs/inode.c
+++ b/fs/isofs/inode.c
@@ -28,14 +28,26 @@
 
 static int isofs_hashi(struct dentry *parent, struct qstr *qstr);
 static int isofs_hash(struct dentry *parent, struct qstr *qstr);
-static int isofs_dentry_cmpi(struct dentry *dentry, struct qstr *a, struct qstr *b);
-static int isofs_dentry_cmp(struct dentry *dentry, struct qstr *a, struct qstr *b);
+static int isofs_dentry_cmpi(const struct dentry *parent,
+                const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name);
+static int isofs_dentry_cmp(const struct dentry *parent,
+                const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name);
 
 #ifdef CONFIG_JOLIET
 static int isofs_hashi_ms(struct dentry *parent, struct qstr *qstr);
 static int isofs_hash_ms(struct dentry *parent, struct qstr *qstr);
-static int isofs_dentry_cmpi_ms(struct dentry *dentry, struct qstr *a, struct qstr *b);
-static int isofs_dentry_cmp_ms(struct dentry *dentry, struct qstr *a, struct qstr *b);
+static int isofs_dentry_cmpi_ms(const struct dentry *parent,
+                const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name);
+static int isofs_dentry_cmp_ms(const struct dentry *parent,
+                const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name);
 #endif
 
 static void isofs_put_super(struct super_block *sb)
@@ -206,49 +218,31 @@ isofs_hashi_common(struct dentry *dentry, struct qstr *qstr, int ms)
 }
 
 /*
- * Case insensitive compare of two isofs names.
+ * Compare of two isofs names.
  */
-static int isofs_dentry_cmpi_common(struct dentry *dentry, struct qstr *a,
-                                struct qstr *b, int ms)
+static int isofs_dentry_cmp_common(
+                unsigned int len, const char *str,
+                const struct qstr *name, int ms, int ci)
 {
         int alen, blen;
 
         /* A filename cannot end in '.' or we treat it like it has none */
-        alen = a->len;
-        blen = b->len;
+        alen = name->len;
+        blen = len;
         if (ms) {
-                while (alen && a->name[alen-1] == '.')
+                while (alen && name->name[alen-1] == '.')
                         alen--;
-                while (blen && b->name[blen-1] == '.')
+                while (blen && str[blen-1] == '.')
                         blen--;
         }
         if (alen == blen) {
-                if (strnicmp(a->name, b->name, alen) == 0)
-                        return 0;
-        }
-        return 1;
-}
-
-/*
- * Case sensitive compare of two isofs names.
- */
-static int isofs_dentry_cmp_common(struct dentry *dentry, struct qstr *a,
-                                        struct qstr *b, int ms)
-{
-        int alen, blen;
-
-        /* A filename cannot end in '.' or we treat it like it has none */
-        alen = a->len;
-        blen = b->len;
-        if (ms) {
-                while (alen && a->name[alen-1] == '.')
-                        alen--;
-                while (blen && b->name[blen-1] == '.')
-                        blen--;
-        }
-        if (alen == blen) {
-                if (strncmp(a->name, b->name, alen) == 0)
-                        return 0;
+                if (ci) {
+                        if (strnicmp(name->name, str, alen) == 0)
+                                return 0;
+                } else {
+                        if (strncmp(name->name, str, alen) == 0)
+                                return 0;
+                }
         }
         return 1;
 }
@@ -266,15 +260,19 @@ isofs_hashi(struct dentry *dentry, struct qstr *qstr)
 }
 
 static int
-isofs_dentry_cmp(struct dentry *dentry,struct qstr *a,struct qstr *b)
+isofs_dentry_cmp(const struct dentry *parent, const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name)
 {
-        return isofs_dentry_cmp_common(dentry, a, b, 0);
+        return isofs_dentry_cmp_common(len, str, name, 0, 0);
 }
 
 static int
-isofs_dentry_cmpi(struct dentry *dentry,struct qstr *a,struct qstr *b)
+isofs_dentry_cmpi(const struct dentry *parent, const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name)
 {
-        return isofs_dentry_cmpi_common(dentry, a, b, 0);
+        return isofs_dentry_cmp_common(len, str, name, 0, 1);
 }
 
 #ifdef CONFIG_JOLIET
@@ -291,15 +289,19 @@ isofs_hashi_ms(struct dentry *dentry, struct qstr *qstr)
 }
 
 static int
-isofs_dentry_cmp_ms(struct dentry *dentry,struct qstr *a,struct qstr *b)
+isofs_dentry_cmp_ms(const struct dentry *parent, const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name)
 {
-        return isofs_dentry_cmp_common(dentry, a, b, 1);
+        return isofs_dentry_cmp_common(len, str, name, 1, 0);
 }
 
 static int
-isofs_dentry_cmpi_ms(struct dentry *dentry,struct qstr *a,struct qstr *b)
+isofs_dentry_cmpi_ms(const struct dentry *parent, const struct inode *pinode,
+                const struct dentry *dentry, const struct inode *inode,
+                unsigned int len, const char *str, const struct qstr *name)
 {
-        return isofs_dentry_cmpi_common(dentry, a, b, 1);
+        return isofs_dentry_cmp_common(len, str, name, 1, 1);
 }
 #endif
 
diff --git a/fs/isofs/namei.c b/fs/isofs/namei.c
index 0d23abfd4280..715f7d318046 100644
--- a/fs/isofs/namei.c
+++ b/fs/isofs/namei.c
@@ -37,7 +37,8 @@ isofs_cmp(struct dentry *dentry, const char *compare, int dlen)
 
         qstr.name = compare;
         qstr.len = dlen;
-        return dentry->d_op->d_compare(dentry, &dentry->d_name, &qstr);
+        return dentry->d_op->d_compare(NULL, NULL, NULL, NULL,
+                        dentry->d_name.len, dentry->d_name.name, &qstr);
 }
 
 /*