Btrfs: avoid tree log commit when there are no changes

rpm has a habit of running fdatasync when the file hasn't
changed.  We already detect if a file hasn't been changed
in the current transaction but it might have been sent to
the tree-log in this transaction and not changed since
the last call to fsync.

In this case, we want to avoid a tree log sync, which includes
a number of synchronous writes and barriers.  This commit
extends the existing tracking of the last transaction to change
a file to also track the last sub-transaction.

The end result is that rpm -ivh and -Uvh are roughly twice as fast,
and on par with ext3.

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index c71abec..f6783a4 100644 (file)
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -86,6 +86,12 @@ struct btrfs_inode {
         * transid of the trans_handle that last modified this inode
         */
        u64 last_trans;
+
+       /*
+        * log transid when this inode was last modified
+        */
+       u64 last_sub_trans;
+
        /*
         * transid that last logged this inode
         */

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 36a19cd..d0cede5 100644 (file)
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1009,6 +1009,7 @@ struct btrfs_root {
        atomic_t log_writers;
        atomic_t log_commit[2];
        unsigned long log_transid;
+       unsigned long last_log_commit;
        unsigned long log_batch;
        pid_t log_start_pid;
        bool log_multiple_pids;

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ac8927b..d4132aa 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -919,6 +919,7 @@ static int __setup_root(u32 nodesize, u32 leafsize, u32 sectorsize,
        atomic_set(&root->log_writers, 0);
        root->log_batch = 0;
        root->log_transid = 0;
+       root->last_log_commit = 0;
        extent_io_tree_init(&root->dirty_log_pages,
                             fs_info->btree_inode->i_mapping, GFP_NOFS);
 
@@ -1089,6 +1090,7 @@ int btrfs_add_log_tree(struct btrfs_trans_handle *trans,
        WARN_ON(root->log_root);
        root->log_root = log_root;
        root->log_transid = 0;
+       root->last_log_commit = 0;
        return 0;
 }
 

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 53fb1c9..4599113 100644 (file)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1087,8 +1087,10 @@ out_nolock:
                                        btrfs_end_transaction(trans, root);
                                else
                                        btrfs_commit_transaction(trans, root);
-                       } else {
+                       } else if (ret != BTRFS_NO_LOG_SYNC) {
                                btrfs_commit_transaction(trans, root);
+                       } else {
+                               btrfs_end_transaction(trans, root);
                        }
                }
                if (file->f_flags & O_DIRECT) {
@@ -1138,6 +1140,13 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        int ret = 0;
        struct btrfs_trans_handle *trans;
 
+
+       /* we wait first, since the writeback may change the inode */
+       root->log_batch++;
+       /* the VFS called filemap_fdatawrite for us */
+       btrfs_wait_ordered_range(inode, 0, (u64)-1);
+       root->log_batch++;
+
        /*
         * check the transaction that last modified this inode
         * and see if its already been committed
@@ -1145,6 +1154,11 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        if (!BTRFS_I(inode)->last_trans)
                goto out;
 
+       /*
+        * if the last transaction that changed this file was before
+        * the current transaction, we can bail out now without any
+        * syncing
+        */
        mutex_lock(&root->fs_info->trans_mutex);
        if (BTRFS_I(inode)->last_trans <=
            root->fs_info->last_trans_committed) {
@@ -1154,13 +1168,6 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
        }
        mutex_unlock(&root->fs_info->trans_mutex);
 
-       root->log_batch++;
-       filemap_fdatawrite(inode->i_mapping);
-       btrfs_wait_ordered_range(inode, 0, (u64)-1);
-       root->log_batch++;
-
-       if (datasync && !(inode->i_state & I_DIRTY_PAGES))
-               goto out;
        /*
         * ok we haven't committed the transaction yet, lets do a commit
         */
@@ -1189,14 +1196,18 @@ int btrfs_sync_file(struct file *file, struct dentry *dentry, int datasync)
         */
        mutex_unlock(&dentry->d_inode->i_mutex);
 
-       if (ret > 0) {
-               ret = btrfs_commit_transaction(trans, root);
-       } else {
-               ret = btrfs_sync_log(trans, root);
-               if (ret == 0)
-                       ret = btrfs_end_transaction(trans, root);
-               else
+       if (ret != BTRFS_NO_LOG_SYNC) {
+               if (ret > 0) {
                        ret = btrfs_commit_transaction(trans, root);
+               } else {
+                       ret = btrfs_sync_log(trans, root);
+                       if (ret == 0)
+                               ret = btrfs_end_transaction(trans, root);
+                       else
+                               ret = btrfs_commit_transaction(trans, root);
+               }
+       } else {
+               ret = btrfs_end_transaction(trans, root);
        }
        mutex_lock(&dentry->d_inode->i_mutex);
 out:

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index ef399a7..5b9567c 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -3480,6 +3480,7 @@ static noinline void init_btrfs_i(struct inode *inode)
        bi->generation = 0;
        bi->sequence = 0;
        bi->last_trans = 0;
+       bi->last_sub_trans = 0;
        bi->logged_trans = 0;
        bi->delalloc_bytes = 0;
        bi->reserved_bytes = 0;
@@ -4980,7 +4981,9 @@ again:
        set_page_dirty(page);
        SetPageUptodate(page);
 
-       BTRFS_I(inode)->last_trans = root->fs_info->generation + 1;
+       BTRFS_I(inode)->last_trans = root->fs_info->generation;
+       BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;
+
        unlock_extent(io_tree, page_start, page_end, GFP_NOFS);
 
 out_unlock:
@@ -5100,6 +5103,7 @@ struct inode *btrfs_alloc_inode(struct super_block *sb)
        if (!ei)
                return NULL;
        ei->last_trans = 0;
+       ei->last_sub_trans = 0;
        ei->logged_trans = 0;
        ei->outstanding_extents = 0;
        ei->reserved_extents = 0;

diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index 663c674..f68cbbe 100644 (file)
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -79,6 +79,7 @@ static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
                                              struct inode *inode)
 {
        BTRFS_I(inode)->last_trans = trans->transaction->transid;
+       BTRFS_I(inode)->last_sub_trans = BTRFS_I(inode)->root->log_transid;
 }
 
 int btrfs_end_transaction(struct btrfs_trans_handle *trans,

diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c
index 6d9ec28..0a1bde2 100644 (file)
--- a/fs/btrfs/tree-log.c
+++ b/fs/btrfs/tree-log.c
@@ -1980,6 +1980,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        int ret;
        struct btrfs_root *log = root->log_root;
        struct btrfs_root *log_root_tree = root->fs_info->log_root_tree;
+       u64 log_transid = 0;
 
        mutex_lock(&root->log_mutex);
        index1 = root->log_transid % 2;
@@ -2018,6 +2019,7 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        btrfs_set_root_node(&log->root_item, log->node);
 
        root->log_batch = 0;
+       log_transid = root->log_transid;
        root->log_transid++;
        log->log_transid = root->log_transid;
        root->log_start_pid = 0;
@@ -2095,6 +2097,11 @@ int btrfs_sync_log(struct btrfs_trans_handle *trans,
        write_ctree_super(trans, root->fs_info->tree_root, 1);
        ret = 0;
 
+       mutex_lock(&root->log_mutex);
+       if (root->last_log_commit < log_transid)
+               root->last_log_commit = log_transid;
+       mutex_unlock(&root->log_mutex);
+
 out_wake_log_root:
        atomic_set(&log_root_tree->log_commit[index2], 0);
        smp_mb();
@@ -2862,6 +2869,21 @@ out:
        return ret;
 }
 
+static int inode_in_log(struct btrfs_trans_handle *trans,
+                struct inode *inode)
+{
+       struct btrfs_root *root = BTRFS_I(inode)->root;
+       int ret = 0;
+
+       mutex_lock(&root->log_mutex);
+       if (BTRFS_I(inode)->logged_trans == trans->transid &&
+           BTRFS_I(inode)->last_sub_trans <= root->last_log_commit)
+               ret = 1;
+       mutex_unlock(&root->log_mutex);
+       return ret;
+}
+
+
 /*
  * helper function around btrfs_log_inode to make sure newly created
  * parent directories also end up in the log.  A minimal inode and backref
@@ -2901,6 +2923,11 @@ int btrfs_log_inode_parent(struct btrfs_trans_handle *trans,
        if (ret)
                goto end_no_trans;
 
+       if (inode_in_log(trans, inode)) {
+               ret = BTRFS_NO_LOG_SYNC;
+               goto end_no_trans;
+       }
+
        start_log_trans(trans, root);
 
        ret = btrfs_log_inode(trans, root, inode, inode_only);

diff --git a/fs/btrfs/tree-log.h b/fs/btrfs/tree-log.h
index d09c760..0776eac 100644 (file)
--- a/fs/btrfs/tree-log.h
+++ b/fs/btrfs/tree-log.h
@@ -19,6 +19,9 @@
 #ifndef __TREE_LOG_
 #define __TREE_LOG_
 
+/* return value for btrfs_log_dentry_safe that means we don't need to log it at all */
+#define BTRFS_NO_LOG_SYNC 256
+
 int btrfs_sync_log(struct btrfs_trans_handle *trans,
                   struct btrfs_root *root);
 int btrfs_free_log(struct btrfs_trans_handle *trans, struct btrfs_root *root);