This feature flag indicates that all directory entry nodes have a 32bit
cookie set and therefore UBIFS is allowed to perform lookups by hash.

Signed-off-by: Richard Weinberger <rich...@nod.at>
---
 fs/ubifs/journal.c     | 14 +++++++++++---
 fs/ubifs/sb.c          |  2 ++
 fs/ubifs/tnc.c         |  3 +++
 fs/ubifs/ubifs-media.h |  3 +++
 fs/ubifs/ubifs.h       |  2 ++
 5 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/ubifs/journal.c b/fs/ubifs/journal.c
index 88d33775f18b..a459211a1c21 100644
--- a/fs/ubifs/journal.c
+++ b/fs/ubifs/journal.c
@@ -501,6 +501,14 @@ static void mark_inode_clean(struct ubifs_info *c, struct 
ubifs_inode *ui)
        ui->dirty = 0;
 }
 
+static void set_dent_cookie(struct ubifs_info *c, struct ubifs_dent_node *dent)
+{
+       if (c->double_hash)
+               dent->cookie = prandom_u32();
+       else
+               dent->cookie = 0;
+}
+
 /**
  * ubifs_jnl_update - update inode.
  * @c: UBIFS file-system description object
@@ -589,7 +597,7 @@ int ubifs_jnl_update(struct ubifs_info *c, const struct 
inode *dir,
        dent->nlen = cpu_to_le16(fname_len(nm));
        memcpy(dent->name, fname_name(nm), fname_len(nm));
        dent->name[fname_len(nm)] = '\0';
-       dent->cookie = prandom_u32();
+       set_dent_cookie(c, dent);
 
        zero_dent_node_unused(dent);
        ubifs_prep_grp_node(c, dent, dlen, 0);
@@ -1125,7 +1133,7 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct 
inode *old_dir,
        dent->nlen = cpu_to_le16(fname_len(new_nm));
        memcpy(dent->name, fname_name(new_nm), fname_len(new_nm));
        dent->name[fname_len(new_nm)] = '\0';
-       dent->cookie = prandom_u32();
+       set_dent_cookie(c, dent);
        zero_dent_node_unused(dent);
        ubifs_prep_grp_node(c, dent, dlen1, 0);
 
@@ -1144,7 +1152,7 @@ int ubifs_jnl_rename(struct ubifs_info *c, const struct 
inode *old_dir,
        dent2->nlen = cpu_to_le16(fname_len(old_nm));
        memcpy(dent2->name, fname_name(old_nm), fname_len(old_nm));
        dent2->name[fname_len(old_nm)] = '\0';
-       dent2->cookie = prandom_u32();
+       set_dent_cookie(c, dent2);
        zero_dent_node_unused(dent2);
        ubifs_prep_grp_node(c, dent2, dlen2, 0);
 
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 3cbb904a6d7d..4a2b4c361587 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -163,6 +163,7 @@ static int create_default_filesystem(struct ubifs_info *c)
        tmp64 = (long long)max_buds * c->leb_size;
        if (big_lpt)
                sup_flags |= UBIFS_FLG_BIGLPT;
+       sup_flags |= UBIFS_FLG_DOUBLE_HASH;
 
        sup->ch.node_type  = UBIFS_SB_NODE;
        sup->key_hash      = UBIFS_KEY_HASH_R5;
@@ -620,6 +621,7 @@ int ubifs_read_superblock(struct ubifs_info *c)
        memcpy(&c->uuid, &sup->uuid, 16);
        c->big_lpt = !!(sup_flags & UBIFS_FLG_BIGLPT);
        c->space_fixup = !!(sup_flags & UBIFS_FLG_SPACE_FIXUP);
+       c->double_hash = !!(sup_flags & UBIFS_FLG_DOUBLE_HASH);
 
        /* Automatically increase file system size to the maximum size */
        c->old_leb_cnt = c->leb_cnt;
diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 1bba4c8b5d3d..74ae2de949df 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -1930,6 +1930,9 @@ int ubifs_tnc_lookup_dh(struct ubifs_info *c, const union 
ubifs_key *key,
        int err;
        const struct ubifs_dent_node *dent = node;
 
+       if (!c->double_hash)
+               return -EOPNOTSUPP;
+
        /*
         * We assume that in most of the cases there are no name collisions and
         * 'ubifs_tnc_lookup()' returns us the right direntry.
diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index 249124d9a801..0cbdc6b70a00 100644
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -418,10 +418,13 @@ enum {
  *
  * UBIFS_FLG_BIGLPT: if "big" LPT model is used if set
  * UBIFS_FLG_SPACE_FIXUP: first-mount "fixup" of free space within LEBs needed
+ * UBIFS_FLG_DOUBLE_HASH: store a 32bit cookie in directory entry nodes to
+ *                       support 64bit cookies for lookups by hash
  */
 enum {
        UBIFS_FLG_BIGLPT = 0x02,
        UBIFS_FLG_SPACE_FIXUP = 0x04,
+       UBIFS_FLG_DOUBLE_HASH = 0x08,
 };
 
 /**
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 85c74ad98898..1b4c86ddd9e2 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1015,6 +1015,7 @@ struct ubifs_debug_info;
  *
  * @big_lpt: flag that LPT is too big to write whole during commit
  * @space_fixup: flag indicating that free space in LEBs needs to be cleaned up
+ * @double_hash: flag indicating that we can do lookups by hash
  * @no_chk_data_crc: do not check CRCs when reading data nodes (except during
  *                   recovery)
  * @bulk_read: enable bulk-reads
@@ -1257,6 +1258,7 @@ struct ubifs_info {
 
        unsigned int big_lpt:1;
        unsigned int space_fixup:1;
+       unsigned int double_hash:1;
        unsigned int no_chk_data_crc:1;
        unsigned int bulk_read:1;
        unsigned int default_compr:2;
-- 
2.7.3

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