[patch 2/3] ocfs2: fix write() performance regression

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



-stable review patch.  If anyone has any objections, please let us know.

------------------
From: Mark Fasheh <[email protected]>

patch 4e9563fd55ff4479f2b118d0757d121dd0cfc39c in mainline.

ocfs2: fix write() performance regression

On file systems which don't support sparse files, Ocfs2_map_page_blocks()
was reading blocks on appending writes. This caused write performance to
suffer dramatically. Fix this by detecting an appending write on a nonsparse
fs and skipping the read.

Signed-off-by: Mark Fasheh <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 fs/ocfs2/aops.c |   22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -661,6 +661,27 @@ static void ocfs2_clear_page_regions(str
 }
 
 /*
+ * Nonsparse file systems fully allocate before we get to the write
+ * code. This prevents ocfs2_write() from tagging the write as an
+ * allocating one, which means ocfs2_map_page_blocks() might try to
+ * read-in the blocks at the tail of our file. Avoid reading them by
+ * testing i_size against each block offset.
+ */
+static int ocfs2_should_read_blk(struct inode *inode, struct page *page,
+				 unsigned int block_start)
+{
+	u64 offset = page_offset(page) + block_start;
+
+	if (ocfs2_sparse_alloc(OCFS2_SB(inode->i_sb)))
+		return 1;
+
+	if (i_size_read(inode) > offset)
+		return 1;
+
+	return 0;
+}
+
+/*
  * Some of this taken from block_prepare_write(). We already have our
  * mapping by now though, and the entire write will be allocating or
  * it won't, so not much need to use BH_New.
@@ -713,6 +734,7 @@ int ocfs2_map_page_blocks(struct page *p
 				set_buffer_uptodate(bh);
 		} else if (!buffer_uptodate(bh) && !buffer_delay(bh) &&
 			   !buffer_new(bh) &&
+			   ocfs2_should_read_blk(inode, page, block_start) &&
 			   (block_start < from || block_end > to)) {
 			ll_rw_block(READ, 1, &bh);
 			*wait_bh++=bh;

-- 
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux