[LogFS] Only write journal if dirty

This prevents unnecessary journal writes.  More importantly it prevents
an oops due to a journal write on failed mount.

6 files changed, 19 insertions, 13 deletions

diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c
index b3656c44190e..92949f95a901 100644
--- a/fs/logfs/gc.c
+++ b/fs/logfs/gc.c
@@ -469,7 +469,7 @@ static void __logfs_gc_pass(struct super_block *sb, int target)
 
                 /* Sync in-memory state with on-medium state in case they
                  * diverged */
-                logfs_write_anchor(super->s_master_inode);
+                logfs_write_anchor(sb);
                 round += logfs_scan_some(sb);
                 if (no_free_segments(sb) >= target)
                         goto write_alias;
@@ -613,8 +613,8 @@ void logfs_gc_pass(struct super_block *sb)
          */
         if (super->s_dirty_used_bytes + super->s_dirty_free_bytes
                         + LOGFS_MAX_OBJECTSIZE >= super->s_free_bytes)
-                logfs_write_anchor(super->s_master_inode);
-        __logfs_gc_pass(sb, logfs_super(sb)->s_total_levels);
+                logfs_write_anchor(sb);
+        __logfs_gc_pass(sb, super->s_total_levels);
         logfs_wl_pass(sb);
         logfs_journal_wl_pass(sb);
 }
diff --git a/fs/logfs/journal.c b/fs/logfs/journal.c
index c0e7d63221d4..57eb4fb444a9 100644
--- a/fs/logfs/journal.c
+++ b/fs/logfs/journal.c
@@ -724,14 +724,17 @@ static int logfs_write_obj_aliases(struct super_block *sb)
  * bit wasteful, but robustness is more important.  With this we can *always*
  * erase all journal segments except the one containing the most recent commit.
  */
-void logfs_write_anchor(struct inode *inode)
+void logfs_write_anchor(struct super_block *sb)
 {
-        struct super_block *sb = inode->i_sb;
         struct logfs_super *super = logfs_super(sb);
         struct logfs_area *area = super->s_journal_area;
         int i, err;
 
-        BUG_ON(logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
+        if (!(super->s_flags & LOGFS_SB_FLAG_DIRTY))
+                return;
+        super->s_flags &= ~LOGFS_SB_FLAG_DIRTY;
+
+        BUG_ON(super->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
         mutex_lock(&super->s_journal_mutex);
 
         /* Do this first or suffer corruption */
@@ -821,7 +824,7 @@ void do_logfs_journal_wl_pass(struct super_block *sb)
         area->a_is_open = 0;
         area->a_used_bytes = 0;
         /* Write journal */
-        logfs_write_anchor(super->s_master_inode);
+        logfs_write_anchor(sb);
         /* Write superblocks */
         err = logfs_write_sb(sb);
         BUG_ON(err);
diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h
index 72592114a28f..129779431373 100644
--- a/fs/logfs/logfs.h
+++ b/fs/logfs/logfs.h
@@ -82,7 +82,7 @@
 
 /* Read-only filesystem */
 #define LOGFS_SB_FLAG_RO        0x0001
-#define LOGFS_SB_FLAG_SEG_ALIAS 0x0002
+#define LOGFS_SB_FLAG_DIRTY     0x0002
 #define LOGFS_SB_FLAG_OBJ_ALIAS 0x0004
 #define LOGFS_SB_FLAG_SHUTDOWN  0x0008
 
@@ -526,7 +526,7 @@ void logfs_delete_inode(struct inode *inode);
 void logfs_clear_inode(struct inode *inode);
 
 /* journal.c */
-void logfs_write_anchor(struct inode *inode);
+void logfs_write_anchor(struct super_block *sb);
 int logfs_init_journal(struct super_block *sb);
 void logfs_cleanup_journal(struct super_block *sb);
 int write_alias_journal(struct super_block *sb, u64 ino, u64 bix,
diff --git a/fs/logfs/readwrite.c b/fs/logfs/readwrite.c
index 1dbe6e8cccec..7a23b3e7c0a7 100644
--- a/fs/logfs/readwrite.c
+++ b/fs/logfs/readwrite.c
@@ -421,7 +421,7 @@ static void inode_write_block(struct logfs_block *block)
 
         inode = block->inode;
         if (inode->i_ino == LOGFS_INO_MASTER)
-                logfs_write_anchor(inode);
+                logfs_write_anchor(inode->i_sb);
         else {
                 ret = __logfs_write_inode(inode, 0);
                 /* see indirect_write_block comment */
diff --git a/fs/logfs/segment.c b/fs/logfs/segment.c
index 664cd0dd3576..1a14f9910d55 100644
--- a/fs/logfs/segment.c
+++ b/fs/logfs/segment.c
@@ -352,7 +352,8 @@ int logfs_segment_write(struct inode *inode, struct page *page,
         int ret;
         void *buf;
 
-        BUG_ON(logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
+        super->s_flags |= LOGFS_SB_FLAG_DIRTY;
+        BUG_ON(super->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
         do_compress = logfs_inode(inode)->li_flags & LOGFS_IF_COMPRESSED;
         if (shadow->gc_level != 0) {
                 /* temporarily disable compression for indirect blocks */
@@ -653,11 +654,13 @@ int logfs_segment_read(struct inode *inode, struct page *page,
 int logfs_segment_delete(struct inode *inode, struct logfs_shadow *shadow)
 {
         struct super_block *sb = inode->i_sb;
+        struct logfs_super *super = logfs_super(sb);
         struct logfs_object_header h;
         u16 len;
         int err;
 
-        BUG_ON(logfs_super(sb)->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
+        super->s_flags |= LOGFS_SB_FLAG_DIRTY;
+        BUG_ON(super->s_flags & LOGFS_SB_FLAG_SHUTDOWN);
         BUG_ON(shadow->old_ofs & LOGFS_FULLY_POPULATED);
         if (!shadow->old_ofs)
                 return 0;
diff --git a/fs/logfs/super.c b/fs/logfs/super.c
index 94d80f7ee7c2..1d081b7ede5a 100644
--- a/fs/logfs/super.c
+++ b/fs/logfs/super.c
@@ -490,7 +490,7 @@ static void logfs_kill_sb(struct super_block *sb)
         log_super("LogFS: Start unmounting\n");
         /* Alias entries slow down mount, so evict as many as possible */
         sync_filesystem(sb);
-        logfs_write_anchor(super->s_master_inode);
+        logfs_write_anchor(sb);
 
         /*
          * From this point on alias entries are simply dropped - and any