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>

1 files changed, 28 insertions, 18 deletions

diff --git a/fs/affs/namei.c b/fs/affs/namei.c
index 914d1c0bc07a..547d5deb0d42 100644
--- a/fs/affs/namei.c
+++ b/fs/affs/namei.c
@@ -14,10 +14,16 @@ typedef int (*toupper_t)(int);
 
 static int       affs_toupper(int ch);
 static int       affs_hash_dentry(struct dentry *, struct qstr *);
-static int       affs_compare_dentry(struct dentry *, struct qstr *, struct qstr *);
+static int       affs_compare_dentry(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       affs_intl_toupper(int ch);
 static int       affs_intl_hash_dentry(struct dentry *, struct qstr *);
-static int       affs_intl_compare_dentry(struct dentry *, struct qstr *, struct qstr *);
+static int       affs_intl_compare_dentry(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);
 
 const struct dentry_operations affs_dentry_operations = {
         .d_hash         = affs_hash_dentry,
@@ -88,29 +94,29 @@ affs_intl_hash_dentry(struct dentry *dentry, struct qstr *qstr)
         return __affs_hash_dentry(dentry, qstr, affs_intl_toupper);
 }
 
-static inline int
-__affs_compare_dentry(struct dentry *dentry, struct qstr *a, struct qstr *b, toupper_t toupper)
+static inline int __affs_compare_dentry(unsigned int len,
+                const char *str, const struct qstr *name, toupper_t toupper)
 {
-        const u8 *aname = a->name;
-        const u8 *bname = b->name;
-        int len;
+        const u8 *aname = str;
+        const u8 *bname = name->name;
 
-        /* 'a' is the qstr of an already existing dentry, so the name
-         * must be valid. 'b' must be validated first.
+        /*
+         * 'str' is the name of an already existing dentry, so the name
+         * must be valid. 'name' must be validated first.
          */
 
-        if (affs_check_name(b->name,b->len))
+        if (affs_check_name(name->name, name->len))
                 return 1;
 
-        /* If the names are longer than the allowed 30 chars,
+        /*
+         * If the names are longer than the allowed 30 chars,
          * the excess is ignored, so their length may differ.
          */
-        len = a->len;
         if (len >= 30) {
-                if (b->len < 30)
+                if (name->len < 30)
                         return 1;
                 len = 30;
-        } else if (len != b->len)
+        } else if (len != name->len)
                 return 1;
 
         for (; len > 0; len--)
@@ -121,14 +127,18 @@ __affs_compare_dentry(struct dentry *dentry, struct qstr *a, struct qstr *b, tou
 }
 
 static int
-affs_compare_dentry(struct dentry *dentry, struct qstr *a, struct qstr *b)
+affs_compare_dentry(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 __affs_compare_dentry(dentry, a, b, affs_toupper);
+        return __affs_compare_dentry(len, str, name, affs_toupper);
 }
 static int
-affs_intl_compare_dentry(struct dentry *dentry, struct qstr *a, struct qstr *b)
+affs_intl_compare_dentry(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 __affs_compare_dentry(dentry, a, b, affs_intl_toupper);
+        return __affs_compare_dentry(len, str, name, affs_intl_toupper);
 }
 
 /*