ext4: re-inline ext4_rec_len_(to|from)_disk functions

commit 3d0518f4, "ext4: New rec_len encoding for very
large blocksizes" made several changes to this path, but from
a perf perspective, un-inlining ext4_rec_len_from_disk() seems
most significant.  This function is called from ext4_check_dir_entry(),
which on a file-creation workload is called extremely often.

I tested this with bonnie:

# bonnie++ -u root -s 0 -f -x 200 -d /mnt/test -n 32

(this does 200 iterations) and got this for the file creations:

ext4 stock:   Average =  21206.8 files/s
ext4 inlined: Average =  22346.7 files/s  (+5%)

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 37 insertions, 2 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ed14e1db083..e03841d9f30 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1412,6 +1412,43 @@ struct ext4_dir_entry_2 {
 #define EXT4_MAX_REC_LEN                ((1<<16)-1)
 
 /*
+ * If we ever get support for fs block sizes > page_size, we'll need
+ * to remove the #if statements in the next two functions...
+ */
+static inline unsigned int
+ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize)
+{
+        unsigned len = le16_to_cpu(dlen);
+
+#if (PAGE_CACHE_SIZE >= 65536)
+        if (len == EXT4_MAX_REC_LEN || len == 0)
+                return blocksize;
+        return (len & 65532) | ((len & 3) << 16);
+#else
+        return len;
+#endif
+}
+
+static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
+{
+        if ((len > blocksize) || (blocksize > (1 << 18)) || (len & 3))
+                BUG();
+#if (PAGE_CACHE_SIZE >= 65536)
+        if (len < 65536)
+                return cpu_to_le16(len);
+        if (len == blocksize) {
+                if (blocksize == 65536)
+                        return cpu_to_le16(EXT4_MAX_REC_LEN);
+                else
+                        return cpu_to_le16(0);
+        }
+        return cpu_to_le16((len & 65532) | ((len >> 16) & 3));
+#else
+        return cpu_to_le16(len);
+#endif
+}
+
+/*
  * Hash Tree Directory indexing
  * (c) Daniel Phillips, 2001
  */
@@ -1636,8 +1673,6 @@ extern long ext4_compat_ioctl(struct file *, unsigned int, unsigned long);
 extern int ext4_ext_migrate(struct inode *);
 
 /* namei.c */
-extern unsigned int ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize);
-extern __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize);
 extern int ext4_orphan_add(handle_t *, struct inode *);
 extern int ext4_orphan_del(handle_t *, struct inode *);
 extern int ext4_htree_fill_tree(struct file *dir_file, __u32 start_hash,