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[PATCH v2 01/12] xfs: add a helper to figure out the space log reservati

To: xfs@xxxxxxxxxxx
Subject: [PATCH v2 01/12] xfs: add a helper to figure out the space log reservation per item
From: Jeff Liu <jeff.liu@xxxxxxxxxx>
Date: Thu, 10 Jan 2013 21:47:54 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121028 Thunderbird/16.0.2
Add a helper xfs_calc_buf_res() to calcuate out the space log reservations per 
item which were got
involved in a transaction.  It will call the xfs_buf_log_overhead() to figure 
out the extra space
for the struct xfs_buf_log_format that gets written into the log for every 
buffer as well as a little
bit of extra space because there also needs a log opheader, i.e. struct 

Signed-off-by: Jie Liu <jeff.liu@xxxxxxxxxx>
 fs/xfs/xfs_trans.c |   31 +++++++++++++++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c
index 06ed520..6c601ea 100644
--- a/fs/xfs/xfs_trans.c
+++ b/fs/xfs/xfs_trans.c
@@ -37,14 +37,45 @@
 #include "xfs_extent_busy.h"
 #include "xfs_bmap.h"
 #include "xfs_quota.h"
+#include "xfs_qm.h"
 #include "xfs_trans_priv.h"
 #include "xfs_trans_space.h"
 #include "xfs_inode_item.h"
+#include "xfs_log_priv.h"
+#include "xfs_buf_item.h"
 #include "xfs_trace.h"
 kmem_zone_t    *xfs_trans_zone;
 kmem_zone_t    *xfs_log_item_desc_zone;
+ * A buffer has a format structure overhead in the log in addition
+ * to the data, so we need to take this into account when reserving
+ * space in a transaction for a buffer.  Round the space required up
+ * to a multiple of 128 bytes so that we don't change the historical
+ * reservation that has been used for this overhead.
+ */
+STATIC uint
+       return round_up(sizeof(struct xlog_op_header) +
+                       sizeof(struct xfs_buf_log_format), 128);
+ * Calculate out transaction log reservation per item in bytes.
+ *
+ * The nbufs argument is used to indicate the number of items that
+ * will be changed in a transaction.  size is used to tell how many
+ * bytes should be reserved per item.
+ */
+STATIC uint
+       uint            nbufs,
+       uint            size)
+       return nbufs * (size + xfs_buf_log_overhead());
  * Various log reservation values.

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