[lustre-devel] [PATCH 22/27] lustre: lmv: change default hash type to crush

[James Simmons <jsimmons@infradead.org>]

From: Andreas Dilger <adilger@whamcloud.com>

Change the default hash type to CRUSH to minimize the number
of directory entries that need to be migrated.

WC-bug-id: https://jira.whamcloud.com/browse/LU-14459
Lustre-commit: bb60caa1c6e7c14c ("LU-14459 lmv: change default hash type to crush")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/43684
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 fs/lustre/llite/dir.c                   | 26 ++++++++++----------------
 include/uapi/linux/lustre/lustre_user.h |  2 +-
 2 files changed, 11 insertions(+), 17 deletions(-)

diff --git a/fs/lustre/llite/dir.c b/fs/lustre/llite/dir.c
index d7466f3..bd15fee 100644
--- a/fs/lustre/llite/dir.c
+++ b/fs/lustre/llite/dir.c
@@ -417,23 +417,17 @@ static int ll_dir_setdirstripe(struct dentry *dparent, struct lmv_user_md *lump,
 	    !OBD_FAIL_CHECK(OBD_FAIL_LLITE_NO_CHECK_DEAD))
 		return -ENOENT;
 
+	/* MDS < 2.14 doesn't support 'crush' hash type, and cannot handle
+	 * unknown hash if client doesn't set a valid one. switch to fnv_1a_64.
+	 */
 	if (!(exp_connect_flags2(sbi->ll_md_exp) & OBD_CONNECT2_CRUSH)) {
-		if ((lump->lum_hash_type & LMV_HASH_TYPE_MASK) ==
-		     LMV_HASH_TYPE_CRUSH) {
-			/* if server doesn't support 'crush' hash type,
-			 * switch to fnv_1a_64.
-			 */
-			lump->lum_hash_type &= ~LMV_HASH_TYPE_MASK;
-			lump->lum_hash_type |= LMV_HASH_TYPE_FNV_1A_64;
-		} else if ((lump->lum_hash_type & LMV_HASH_TYPE_MASK) ==
-			    LMV_HASH_TYPE_UNKNOWN) {
-			/* from 2.14 MDT will choose default hash type if client
-			 * doesn't set a valid one, while old server doesn't
-			 * handle it.
-			 */
-			lump->lum_hash_type &= ~LMV_HASH_TYPE_MASK;
-			lump->lum_hash_type |= LMV_HASH_TYPE_DEFAULT;
-		}
+		enum lmv_hash_type type = lump->lum_hash_type &
+					  LMV_HASH_TYPE_MASK;
+
+		if (type == LMV_HASH_TYPE_CRUSH ||
+		    type == LMV_HASH_TYPE_UNKNOWN)
+			lump->lum_hash_type = (lump->lum_hash_type ^ type) |
+					      LMV_HASH_TYPE_FNV_1A_64;
 	}
 
 	if (unlikely(!lmv_user_magic_supported(cpu_to_le32(lump->lum_magic))))
diff --git a/include/uapi/linux/lustre/lustre_user.h b/include/uapi/linux/lustre/lustre_user.h
index aae6642..49b013c 100644
--- a/include/uapi/linux/lustre/lustre_user.h
+++ b/include/uapi/linux/lustre/lustre_user.h
@@ -701,7 +701,7 @@ static __attribute__((unused)) const char *mdt_hash_name[] = {
 	"crush",
 };
 
-#define LMV_HASH_TYPE_DEFAULT LMV_HASH_TYPE_FNV_1A_64
+#define LMV_HASH_TYPE_DEFAULT LMV_HASH_TYPE_CRUSH
 
 /* Right now only the lower part(0-16bits) of lmv_hash_type is being used,
  * and the higher part will be the flag to indicate the status of object,
-- 
1.8.3.1

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