ocfs2: Add "preferred slot" mount option

ocfs2 will attempt to assign the node the slot# provided in the mount
option. Failure to assign the preferred slot is not an error. This small
feature can be useful for automated testing.

Signed-off-by: Sunil Mushran <sunil.mushran@oracle.com>
Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

3 files changed, 31 insertions, 5 deletions

diff --git a/fs/ocfs2/ocfs2.h b/fs/ocfs2/ocfs2.h
index a860633e833f..648ef8e45eaa 100644
--- a/fs/ocfs2/ocfs2.h
+++ b/fs/ocfs2/ocfs2.h
@@ -219,6 +219,7 @@ struct ocfs2_super
         u16 max_slots;
         s16 node_num;
         s16 slot_num;
+        s16 preferred_slot;
         int s_sectsize_bits;
         int s_clustersize;
         int s_clustersize_bits;
diff --git a/fs/ocfs2/slot_map.c b/fs/ocfs2/slot_map.c
index d8b79067dc14..af4882b62cfa 100644
--- a/fs/ocfs2/slot_map.c
+++ b/fs/ocfs2/slot_map.c
@@ -121,17 +121,25 @@ static s16 __ocfs2_node_num_to_slot(struct ocfs2_slot_info *si,
         return ret;
 }
 
-static s16 __ocfs2_find_empty_slot(struct ocfs2_slot_info *si)
+static s16 __ocfs2_find_empty_slot(struct ocfs2_slot_info *si, s16 preferred)
 {
         int i;
         s16 ret = OCFS2_INVALID_SLOT;
 
+        if (preferred >= 0 && preferred < si->si_num_slots) {
+                if (OCFS2_INVALID_SLOT == si->si_global_node_nums[preferred]) {
+                        ret = preferred;
+                        goto out;
+                }
+        }
+
         for(i = 0; i < si->si_num_slots; i++) {
                 if (OCFS2_INVALID_SLOT == si->si_global_node_nums[i]) {
                         ret = (s16) i;
                         break;
                 }
         }
+out:
         return ret;
 }
 
@@ -248,7 +256,7 @@ int ocfs2_find_slot(struct ocfs2_super *osb)
         if (slot == OCFS2_INVALID_SLOT) {
                 /* if no slot yet, then just take 1st available
                  * one. */
-                slot = __ocfs2_find_empty_slot(si);
+                slot = __ocfs2_find_empty_slot(si, osb->preferred_slot);
                 if (slot == OCFS2_INVALID_SLOT) {
                         spin_unlock(&si->si_lock);
                         mlog(ML_ERROR, "no free slots available!\n");
diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index 86b559c7dce9..f07718a7552b 100644
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -82,7 +82,8 @@ MODULE_AUTHOR("Oracle");
 MODULE_LICENSE("GPL");
 
 static int ocfs2_parse_options(struct super_block *sb, char *options,
-                               unsigned long *mount_opt, int is_remount);
+                               unsigned long *mount_opt, s16 *slot,
+                               int is_remount);
 static void ocfs2_put_super(struct super_block *sb);
 static int ocfs2_mount_volume(struct super_block *sb);
 static int ocfs2_remount(struct super_block *sb, int *flags, char *data);
@@ -140,6 +141,7 @@ enum {
         Opt_data_ordered,
         Opt_data_writeback,
         Opt_atime_quantum,
+        Opt_slot,
         Opt_err,
 };
 
@@ -154,6 +156,7 @@ static match_table_t tokens = {
         {Opt_data_ordered, "data=ordered"},
         {Opt_data_writeback, "data=writeback"},
         {Opt_atime_quantum, "atime_quantum=%u"},
+        {Opt_slot, "preferred_slot=%u"},
         {Opt_err, NULL}
 };
 
@@ -355,9 +358,10 @@ static int ocfs2_remount(struct super_block *sb, int *flags, char *data)
         int incompat_features;
         int ret = 0;
         unsigned long parsed_options;
+        s16 slot;
         struct ocfs2_super *osb = OCFS2_SB(sb);
 
-        if (!ocfs2_parse_options(sb, data, &parsed_options, 1)) {
+        if (!ocfs2_parse_options(sb, data, &parsed_options, &slot, 1)) {
                 ret = -EINVAL;
                 goto out;
         }
@@ -534,6 +538,7 @@ static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
         struct dentry *root;
         int status, sector_size;
         unsigned long parsed_opt;
+        s16 slot;
         struct inode *inode = NULL;
         struct ocfs2_super *osb = NULL;
         struct buffer_head *bh = NULL;
@@ -541,7 +546,7 @@ static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
 
         mlog_entry("%p, %p, %i", sb, data, silent);
 
-        if (!ocfs2_parse_options(sb, data, &parsed_opt, 0)) {
+        if (!ocfs2_parse_options(sb, data, &parsed_opt, &slot, 0)) {
                 status = -EINVAL;
                 goto read_super_error;
         }
@@ -571,6 +576,7 @@ static int ocfs2_fill_super(struct super_block *sb, void *data, int silent)
         brelse(bh);
         bh = NULL;
         osb->s_mount_opt = parsed_opt;
+        osb->preferred_slot = slot;
 
         sb->s_magic = OCFS2_SUPER_MAGIC;
 
@@ -713,6 +719,7 @@ static struct file_system_type ocfs2_fs_type = {
 static int ocfs2_parse_options(struct super_block *sb,
                                char *options,
                                unsigned long *mount_opt,
+                               s16 *slot,
                                int is_remount)
 {
         int status;
@@ -722,6 +729,7 @@ static int ocfs2_parse_options(struct super_block *sb,
                    options ? options : "(none)");
 
         *mount_opt = 0;
+        *slot = OCFS2_INVALID_SLOT;
 
         if (!options) {
                 status = 1;
@@ -782,6 +790,15 @@ static int ocfs2_parse_options(struct super_block *sb,
                         else
                                 osb->s_atime_quantum = OCFS2_DEFAULT_ATIME_QUANTUM;
                         break;
+                case Opt_slot:
+                        option = 0;
+                        if (match_int(&args[0], &option)) {
+                                status = 0;
+                                goto bail;
+                        }
+                        if (option)
+                                *slot = (s16)option;
+                        break;
                 default:
                         mlog(ML_ERROR,
                              "Unrecognized mount option \"%s\" "