Re: [PATCH 1/2] block: add BH_Meta flag

On 16 May 2012 18:02, Boaz Harrosh [off-list ref] wrote:

On 05/11/2012 06:02 PM, Saugata Das wrote:

quoted

From: Saugata Das <redacted>

Today, storage devices like eMMC has special features like data tagging
(introduced in MMC-4.5 version) in order to improve performance of some
specific writes. On MMC stack, data tagging is used for all writes which
has REQ_META flag set. This patch adds the capability to add REQ_META flag
during meta data write.

Signed-off-by: Saugata Das <redacted>
---
 fs/buffer.c                 |   10 ++++++++--
 include/linux/buffer_head.h |    2 ++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 36d6665..688b38b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c

@@ -1685,7 +1685,10 @@ static int __block_write_full_page(struct inode *inode, struct page *page,

      do {
              struct buffer_head *next = bh->b_this_page;
              if (buffer_async_write(bh)) {
-                     submit_bh(write_op, bh);
+                     if (buffer_meta(bh))
+                             submit_bh(write_op | REQ_META, bh);
+                     else
+                             submit_bh(write_op, bh);

Its not nice to duplicate a call site for the parameter difference
it's better to change the parameter and call the function in one
place. (an assembler call site can get big)

You can do:
+                               submit_bh(write_op | (buffer_meta(bh) << __REQ_META), bh);

And also avoid a conditional inside a loop.

Thanks for your comments. I will take care of this in the next version.

quoted

                      nr_underway++;
              }
              bh = next;

@@ -1739,7 +1742,10 @@ recover:

              struct buffer_head *next = bh->b_this_page;
              if (buffer_async_write(bh)) {
                      clear_buffer_dirty(bh);
-                     submit_bh(write_op, bh);
+                     if (buffer_meta(bh))
+                             submit_bh(write_op | REQ_META, bh);
+                     else
+                             submit_bh(write_op, bh);

Here too

Boaz

quoted

                      nr_underway++;
              }
              bh = next;

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index ef26043..0776564 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h

@@ -34,6 +34,7 @@ enum bh_state_bits {

      BH_Write_EIO,   /* I/O error on write */
      BH_Unwritten,   /* Buffer is allocated on disk but not written */
      BH_Quiet,       /* Buffer Error Prinks to be quiet */
+     BH_Meta,        /* Is meta */

      BH_PrivateStart,/* not a state bit, but the first bit available
                       * for private allocation by other entities

@@ -126,6 +127,7 @@ BUFFER_FNS(Delay, delay)

 BUFFER_FNS(Boundary, boundary)
 BUFFER_FNS(Write_EIO, write_io_error)
 BUFFER_FNS(Unwritten, unwritten)
+BUFFER_FNS(Meta, meta)

 #define bh_offset(bh)                ((unsigned long)(bh)->b_data & ~PAGE_MASK)
 #define touch_buffer(bh)     mark_page_accessed(bh->b_page)

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