nilfs2: get rid of back pointer to writable sb instance

Nilfs object holds a back pointer to a writable super block instance
in nilfs->ns_writer, and this became eliminable since sb is now made
per device and all inodes have a valid pointer to it.

This deletes the ns_writer pointer and a reader/writer semaphore
protecting it.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

5 files changed, 2 insertions, 61 deletions

diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index 32695f3c4b9a..0a2ccfc0d6f9 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -78,25 +78,11 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
                                                      struct buffer_head *,
                                                      void *))
 {
-        struct the_nilfs *nilfs = NILFS_I_NILFS(inode);
         struct super_block *sb = inode->i_sb;
         struct nilfs_transaction_info ti;
         struct buffer_head *bh;
         int err;
 
-        if (!sb) {
-                /*
-                 * Make sure this function is not called from any
-                 * read-only context.
-                 */
-                if (!nilfs->ns_writer) {
-                        WARN_ON(1);
-                        err = -EROFS;
-                        goto out;
-                }
-                sb = nilfs->ns_writer->s_super;
-        }
-
         nilfs_transaction_begin(sb, &ti, 0);
 
         err = -ENOMEM;
@@ -112,7 +98,7 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
         if (buffer_uptodate(bh))
                 goto failed_bh;
 
-        bh->b_bdev = nilfs->ns_bdev;
+        bh->b_bdev = sb->s_bdev;
         err = nilfs_mdt_insert_new_block(inode, block, bh, init_block);
         if (likely(!err)) {
                 get_bh(bh);
@@ -129,7 +115,7 @@ static int nilfs_mdt_create_block(struct inode *inode, unsigned long block,
                 err = nilfs_transaction_commit(sb);
         else
                 nilfs_transaction_abort(sb);
- out:
+
         return err;
 }
 
@@ -398,8 +384,6 @@ nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
 {
         struct inode *inode;
         struct super_block *sb;
-        struct the_nilfs *nilfs;
-        struct nilfs_sb_info *writer = NULL;
         int err = 0;
 
         redirty_page_for_writepage(wbc, page);
@@ -410,25 +394,12 @@ nilfs_mdt_write_page(struct page *page, struct writeback_control *wbc)
                 return 0;
 
         sb = inode->i_sb;
-        nilfs = NILFS_SB(sb)->s_nilfs;
-
-        if (!sb) {
-                down_read(&nilfs->ns_writer_sem);
-                writer = nilfs->ns_writer;
-                if (!writer) {
-                        up_read(&nilfs->ns_writer_sem);
-                        return -EROFS;
-                }
-                sb = writer->s_super;
-        }
 
         if (wbc->sync_mode == WB_SYNC_ALL)
                 err = nilfs_construct_segment(sb);
         else if (wbc->for_reclaim)
                 nilfs_flush_segment(sb, inode->i_ino);
 
-        if (writer)
-                up_read(&nilfs->ns_writer_sem);
         return err;
 }
 
diff --git a/fs/nilfs2/recovery.c b/fs/nilfs2/recovery.c
index dcb5a9812c6c..5d2711c28da7 100644
--- a/fs/nilfs2/recovery.c
+++ b/fs/nilfs2/recovery.c
@@ -440,7 +440,6 @@ static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
         segnum[2] = ri->ri_segnum;
         segnum[3] = ri->ri_nextnum;
 
-        nilfs_attach_writer(nilfs, sbi);
         /*
          * Releasing the next segment of the latest super root.
          * The next segment is invalidated by this recovery.
@@ -480,7 +479,6 @@ static int nilfs_prepare_segment_for_recovery(struct the_nilfs *nilfs,
 
  failed:
         /* No need to recover sufile because it will be destroyed on error */
-        nilfs_detach_writer(nilfs, sbi);
         return err;
 }
 
@@ -599,7 +597,6 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
         };
         int state = RF_INIT_ST;
 
-        nilfs_attach_writer(nilfs, sbi);
         pseg_start = ri->ri_lsegs_start;
         seg_seq = ri->ri_lsegs_start_seq;
         segnum = nilfs_get_segnum_of_block(nilfs, pseg_start);
@@ -690,7 +687,6 @@ static int nilfs_do_roll_forward(struct the_nilfs *nilfs,
  out:
         brelse(bh_sum);
         dispose_recovery_list(&dsync_blocks);
-        nilfs_detach_writer(nilfs, sbi);
         return err;
 
  confused:
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index b0c5e08d06c8..56350bf1f79f 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -2799,7 +2799,6 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
 int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
                                      struct nilfs_root *root)
 {
-        struct the_nilfs *nilfs = sbi->s_nilfs;
         int err;
 
         if (NILFS_SC(sbi)) {
@@ -2815,10 +2814,8 @@ int nilfs_attach_segment_constructor(struct nilfs_sb_info *sbi,
         if (!sbi->s_sc_info)
                 return -ENOMEM;
 
-        nilfs_attach_writer(nilfs, sbi);
         err = nilfs_segctor_start_thread(NILFS_SC(sbi));
         if (err) {
-                nilfs_detach_writer(nilfs, sbi);
                 kfree(sbi->s_sc_info);
                 sbi->s_sc_info = NULL;
         }
@@ -2855,5 +2852,4 @@ void nilfs_detach_segment_constructor(struct nilfs_sb_info *sbi)
         up_write(&nilfs->ns_segctor_sem);
 
         nilfs_dispose_list(sbi, &garbage_list, 1);
-        nilfs_detach_writer(nilfs, sbi);
 }
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 4cc705a1d135..a94aa57c4bd9 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -75,7 +75,6 @@ struct the_nilfs *alloc_nilfs(struct block_device *bdev)
         nilfs->ns_bdev = bdev;
         atomic_set(&nilfs->ns_ndirtyblks, 0);
         init_rwsem(&nilfs->ns_sem);
-        init_rwsem(&nilfs->ns_writer_sem);
         INIT_LIST_HEAD(&nilfs->ns_gc_inodes);
         spin_lock_init(&nilfs->ns_last_segment_lock);
         nilfs->ns_cptree = RB_ROOT;
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index cae56f338b64..bbbc1c748aac 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -48,9 +48,7 @@ enum {
  * @ns_flags: flags
  * @ns_bdev: block device
  * @ns_bdi: backing dev info
- * @ns_writer: back pointer to writable nilfs_sb_info
  * @ns_sem: semaphore for shared states
- * @ns_writer_sem: semaphore protecting ns_writer attach/detach
  * @ns_sbh: buffer heads of on-disk super blocks
  * @ns_sbp: pointers to super block data
  * @ns_sbwtime: previous write time of super block
@@ -93,9 +91,7 @@ struct the_nilfs {
 
         struct block_device    *ns_bdev;
         struct backing_dev_info *ns_bdi;
-        struct nilfs_sb_info   *ns_writer;
         struct rw_semaphore     ns_sem;
-        struct rw_semaphore     ns_writer_sem;
 
         /*
          * used for
@@ -252,23 +248,6 @@ static inline void nilfs_get_root(struct nilfs_root *root)
         atomic_inc(&root->count);
 }
 
-static inline void
-nilfs_attach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
-{
-        down_write(&nilfs->ns_writer_sem);
-        nilfs->ns_writer = sbi;
-        up_write(&nilfs->ns_writer_sem);
-}
-
-static inline void
-nilfs_detach_writer(struct the_nilfs *nilfs, struct nilfs_sb_info *sbi)
-{
-        down_write(&nilfs->ns_writer_sem);
-        if (sbi == nilfs->ns_writer)
-                nilfs->ns_writer = NULL;
-        up_write(&nilfs->ns_writer_sem);
-}
-
 static inline int nilfs_valid_fs(struct the_nilfs *nilfs)
 {
         unsigned valid_fs;