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Re: [PATCH v2 1/2] xfsprogs: sync xfs_calc_buf_res() to the user space

To: Jeff Liu <jeff.liu@xxxxxxxxxx>
Subject: Re: [PATCH v2 1/2] xfsprogs: sync xfs_calc_buf_res() to the user space
From: Mark Tinguely <tinguely@xxxxxxx>
Date: Mon, 28 Jan 2013 08:09:45 -0600
Cc: xfs@xxxxxxxxxxx
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <51067F4B.8000605@xxxxxxxxxx>
References: <51067F4B.8000605@xxxxxxxxxx>
User-agent: Mozilla/5.0 (X11; FreeBSD amd64; rv:9.0) Gecko/20120122 Thunderbird/9.0
On 01/28/13 07:38, Jeff Liu wrote:
Sync the new helper xfs_calc_buf_res() to the user space.

Signed-off-by: Jie Liu<jeff.liu@xxxxxxxxxx>
---
  libxfs/xfs_trans.c |   29 +++++++++++++++++++++++++++++
  1 file changed, 29 insertions(+)

diff --git a/libxfs/xfs_trans.c b/libxfs/xfs_trans.c
index 635de8f..d7ff1a9 100644
--- a/libxfs/xfs_trans.c
+++ b/libxfs/xfs_trans.c
@@ -23,6 +23,35 @@ 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
+xfs_buf_log_overhead(void)
+{
+       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
+xfs_calc_buf_res(
+       uint            nbufs,
+       uint            size)
+{
+       return nbufs * (size + xfs_buf_log_overhead());
+}
+
+/*
   * Various log reservation values.
   *
   * These are based on the size of the file system block because that is what

Looks good.

Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>

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