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authorLinus Torvalds <torvalds@linux-foundation.org>2012-05-11 00:14:12 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-11 06:54:35 +0400
commit26fe575028703948880fce4355a210c76bb0536e (patch)
tree0a7d04289e1eb1f1739659ebc9498d40f2add5da /include/linux/dcache.h
parentee983e89670704b2a05e897b161f2674a42d1508 (diff)
downloadlinux-26fe575028703948880fce4355a210c76bb0536e.tar.xz
vfs: make it possible to access the dentry hash/len as one 64-bit entry
This allows comparing hash and len in one operation on 64-bit architectures. Right now only __d_lookup_rcu() takes advantage of this, since that is the case we care most about. The use of anonymous struct/unions hides the alternate 64-bit approach from most users, the exception being a few cases where we initialize a 'struct qstr' with a static initializer. This makes the problematic cases use a new QSTR_INIT() helper function for that (but initializing just the name pointer with a "{ .name = xyzzy }" initializer remains valid, as does just copying another qstr structure). Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/dcache.h')
-rw-r--r--include/linux/dcache.h19
1 files changed, 17 insertions, 2 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 8239f64d1c2e..094789ff3e9f 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -25,6 +25,13 @@ struct vfsmount;
#define IS_ROOT(x) ((x) == (x)->d_parent)
+/* The hash is always the low bits of hash_len */
+#ifdef __LITTLE_ENDIAN
+ #define HASH_LEN_DECLARE u32 hash; u32 len;
+#else
+ #define HASH_LEN_DECLARE u32 len; u32 hash;
+#endif
+
/*
* "quick string" -- eases parameter passing, but more importantly
* saves "metadata" about the string (ie length and the hash).
@@ -33,11 +40,19 @@ struct vfsmount;
* dentry.
*/
struct qstr {
- unsigned int hash;
- unsigned int len;
+ union {
+ struct {
+ HASH_LEN_DECLARE;
+ };
+ u64 hash_len;
+ };
const unsigned char *name;
};
+#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
+#define hashlen_hash(hashlen) ((u32) (hashlen))
+#define hashlen_len(hashlen) ((u32)((hashlen) >> 32))
+
struct dentry_stat_t {
int nr_dentry;
int nr_unused;