ext4: add nombcache mount option

The main purpose of mb cache is to achieve deduplication in
extended attributes. In use cases where opportunity for deduplication
is unlikely, it only adds overhead.

Add a mount option to explicitly turn off mb cache.

Suggested-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Tahsin Erdogan <tahsin@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 35 insertions, 17 deletions

diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c
index a5ad0ccdd1cb..34fa37e7744c 100644
--- a/fs/ext4/xattr.c
+++ b/fs/ext4/xattr.c
@@ -991,10 +991,13 @@ static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode,
 			set_nlink(ea_inode, 1);
 			ext4_orphan_del(handle, ea_inode);
 
-			hash = ext4_xattr_inode_get_hash(ea_inode);
-			mb_cache_entry_create(ea_inode_cache, GFP_NOFS, hash,
-					      ea_inode->i_ino,
-					      true /* reusable */);
+			if (ea_inode_cache) {
+				hash = ext4_xattr_inode_get_hash(ea_inode);
+				mb_cache_entry_create(ea_inode_cache,
+						      GFP_NOFS, hash,
+						      ea_inode->i_ino,
+						      true /* reusable */);
+			}
 		}
 	} else {
 		WARN_ONCE(ref_count < 0, "EA inode %lu ref_count=%lld",
@@ -1008,9 +1011,11 @@ static int ext4_xattr_inode_update_ref(handle_t *handle, struct inode *ea_inode,
 			clear_nlink(ea_inode);
 			ext4_orphan_add(handle, ea_inode);
 
-			hash = ext4_xattr_inode_get_hash(ea_inode);
-			mb_cache_entry_delete(ea_inode_cache, hash,
-					      ea_inode->i_ino);
+			if (ea_inode_cache) {
+				hash = ext4_xattr_inode_get_hash(ea_inode);
+				mb_cache_entry_delete(ea_inode_cache, hash,
+						      ea_inode->i_ino);
+			}
 		}
 	}
 
@@ -1194,7 +1199,9 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
 		 * This must happen under buffer lock for
 		 * ext4_xattr_block_set() to reliably detect freed block
 		 */
-		mb_cache_entry_delete(ea_block_cache, hash, bh->b_blocknr);
+		if (ea_block_cache)
+			mb_cache_entry_delete(ea_block_cache, hash,
+					      bh->b_blocknr);
 		get_bh(bh);
 		unlock_buffer(bh);
 
@@ -1214,11 +1221,13 @@ ext4_xattr_release_block(handle_t *handle, struct inode *inode,
 		if (ref == EXT4_XATTR_REFCOUNT_MAX - 1) {
 			struct mb_cache_entry *ce;
 
-			ce = mb_cache_entry_get(ea_block_cache, hash,
-						bh->b_blocknr);
-			if (ce) {
-				ce->e_reusable = 1;
-				mb_cache_entry_put(ea_block_cache, ce);
+			if (ea_block_cache) {
+				ce = mb_cache_entry_get(ea_block_cache, hash,
+							bh->b_blocknr);
+				if (ce) {
+					ce->e_reusable = 1;
+					mb_cache_entry_put(ea_block_cache, ce);
+				}
 			}
 		}
 
@@ -1395,6 +1404,9 @@ ext4_xattr_inode_cache_find(struct inode *inode, const void *value,
 	struct mb_cache *ea_inode_cache = EA_INODE_CACHE(inode);
 	void *ea_data;
 
+	if (!ea_inode_cache)
+		return NULL;
+
 	ce = mb_cache_entry_find_first(ea_inode_cache, hash);
 	if (!ce)
 		return NULL;
@@ -1465,8 +1477,9 @@ static int ext4_xattr_inode_lookup_create(handle_t *handle, struct inode *inode,
 		return err;
 	}
 
-	mb_cache_entry_create(EA_INODE_CACHE(inode), GFP_NOFS, hash,
-			      ea_inode->i_ino, true /* reusable */);
+	if (EA_INODE_CACHE(inode))
+		mb_cache_entry_create(EA_INODE_CACHE(inode), GFP_NOFS, hash,
+				      ea_inode->i_ino, true /* reusable */);
 
 	*ret_inode = ea_inode;
 	return 0;
@@ -1793,8 +1806,9 @@ ext4_xattr_block_set(handle_t *handle, struct inode *inode,
 			 * ext4_xattr_block_set() to reliably detect modified
 			 * block
 			 */
-			mb_cache_entry_delete(ea_block_cache, hash,
-					      bs->bh->b_blocknr);
+			if (ea_block_cache)
+				mb_cache_entry_delete(ea_block_cache, hash,
+						      bs->bh->b_blocknr);
 			ea_bdebug(bs->bh, "modifying in-place");
 			error = ext4_xattr_set_entry(i, s, handle, inode,
 						     true /* is_block */);
@@ -2883,6 +2897,8 @@ ext4_xattr_block_cache_insert(struct mb_cache *ea_block_cache,
 		       EXT4_XATTR_REFCOUNT_MAX;
 	int error;
 
+	if (!ea_block_cache)
+		return;
 	error = mb_cache_entry_create(ea_block_cache, GFP_NOFS, hash,
 				      bh->b_blocknr, reusable);
 	if (error) {
@@ -2949,6 +2965,8 @@ ext4_xattr_block_cache_find(struct inode *inode,
 	struct mb_cache_entry *ce;
 	struct mb_cache *ea_block_cache = EA_BLOCK_CACHE(inode);
 
+	if (!ea_block_cache)
+		return NULL;
 	if (!header->h_hash)
 		return NULL;  /* never share */
 	ea_idebug(inode, "looking for cached blocks [%x]", (int)hash);