From 5c264b1519ebc853085ff994d92df96379e3cd50 Mon Sep 17 00:00:00 2001
From: Sage Weil <sage@newdream.net>
Date: Wed, 27 Jan 2010 21:09:15 -0800
Subject: [PATCH] journal: allow pre and post padding for journal payload

Replace the header.alignment fixups with an explicit post_pad.
---
 src/os/FileJournal.cc | 47 ++++++++++++++++++++++++++++---------------
 src/os/FileJournal.h  |  1 +
 2 files changed, 32 insertions(+), 16 deletions(-)

diff --git a/src/os/FileJournal.cc b/src/os/FileJournal.cc
index 48b1ba3b90eac..32973e918ec52 100644
--- a/src/os/FileJournal.cc
+++ b/src/os/FileJournal.cc
@@ -382,9 +382,23 @@ void FileJournal::prepare_multi_write(bufferlist& bl)
     entry_header_t h;
     h.seq = seq;
     h.len = ebl.length();
+    h.pre_pad = 0;
+    h.post_pad = 0;
     h.make_magic(queue_pos, header.fsid);
+
+    // pad?
+    if (queue_pos + size % header.alignment) {
+      h.post_pad = header.alignment - (queue_pos + size % header.alignment);
+      size += h.post_pad;
+      //dout(20) << "   padding with " << pad << " bytes, queue_pos now " << queue_pos << dendl;
+    }
+
     bl.append((const char*)&h, sizeof(h));
     bl.claim_append(ebl);
+    if (h.post_pad) {
+      bufferptr bp = buffer::create_static(h.post_pad, zero_buf);
+      bl.push_back(bp);
+    }
     bl.append((const char*)&h, sizeof(h));
     
     if (writeq.front().fin) {
@@ -398,15 +412,6 @@ void FileJournal::prepare_multi_write(bufferlist& bl)
 
     queue_pos += size;
 
-    // pad...
-    if (queue_pos % header.alignment) {
-      int pad = header.alignment - (queue_pos % header.alignment);
-      bufferptr bp = buffer::create_static(pad, zero_buf);
-      bl.push_back(bp);
-      queue_pos += pad;
-      //dout(20) << "   padding with " << pad << " bytes, queue_pos now " << queue_pos << dendl;
-    }
-
     if (eleft) {
       if (--eleft == 0) {
 	dout(20) << "    hit max events per write " << g_conf.journal_max_write_entries << dendl;
@@ -429,8 +434,8 @@ bool FileJournal::prepare_single_dio_write(bufferlist& bl)
   __u64 seq = writeq.front().seq;
   bufferlist &ebl = writeq.front().bl;
     
-  off64_t size = 2*sizeof(entry_header_t) + ebl.length();
-  size = ROUND_UP_TO(size, header.alignment);
+  off64_t base_size = 2*sizeof(entry_header_t) + ebl.length();
+  off64_t size = ROUND_UP_TO(base_size, header.alignment);
   
   if (!check_for_wrap(seq, &write_pos, size, true))
     return false;
@@ -444,9 +449,11 @@ bool FileJournal::prepare_single_dio_write(bufferlist& bl)
   entry_header_t *h = (entry_header_t*)bp.c_str();
   h->seq = seq;
   h->len = ebl.length();
+  h->pre_pad = 0;
+  h->post_pad = size - base_size;
   h->make_magic(write_pos, header.fsid);
-  ebl.copy(0, ebl.length(), bp.c_str()+sizeof(*h));
-  memcpy(bp.c_str() + sizeof(*h) + ebl.length(), h, sizeof(*h));
+  ebl.copy(0, ebl.length(), bp.c_str()+sizeof(*h)+h->pre_pad);
+  memcpy(bp.c_str() + sizeof(*h) + h->pre_pad + ebl.length() + h->post_pad, h, sizeof(*h));
   bl.push_back(bp);
   
   if (writeq.front().fin) {
@@ -523,7 +530,8 @@ void FileJournal::do_write(bufferlist& bl)
   writing = false;
 
   write_pos += bl.length();
-  write_pos = ROUND_UP_TO(write_pos, header.alignment);
+  //write_pos = ROUND_UP_TO(write_pos, header.alignment);
+  assert(write_pos % header.alignment == 0);
 
   // kick finisher?  
   //  only if we haven't filled up recently!
@@ -698,10 +706,16 @@ bool FileJournal::read_entry(bufferlist& bl, __u64& seq)
     return false;
   }
 
+  if (h.pre_pad)
+    ::lseek64(fd, h.pre_pad, SEEK_CUR);
+
   // body
   bufferptr bp(h.len);
   ::read(fd, bp.c_str(), h.len);
 
+  if (h.post_pad)
+    ::lseek64(fd, h.post_pad, SEEK_CUR);
+
   // footer
   entry_header_t f;
   ::read(fd, &f, sizeof(h));
@@ -736,8 +750,9 @@ bool FileJournal::read_entry(bufferlist& bl, __u64& seq)
   seq = h.seq;
   journalq.push_back(pair<__u64,off64_t>(h.seq, read_pos));
 
-  read_pos += 2*sizeof(entry_header_t) + h.len;
-  read_pos = ROUND_UP_TO(read_pos, header.alignment);
+  read_pos += 2*sizeof(entry_header_t) + h.pre_pad + h.len + h.post_pad;
+  assert(read_pos % header.alignment == 0);
+  //read_pos = ROUND_UP_TO(read_pos, header.alignment);
   
   return true;
 }
diff --git a/src/os/FileJournal.h b/src/os/FileJournal.h
index f083bc7f50b6c..d453fb7985f6d 100644
--- a/src/os/FileJournal.h
+++ b/src/os/FileJournal.h
@@ -49,6 +49,7 @@ public:
   struct entry_header_t {
     uint64_t seq;  // fs op seq #
     uint64_t len;
+    uint64_t pre_pad, post_pad;
     uint64_t magic1;
     uint64_t magic2;
     
-- 
2.39.5