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Date:	Sun, 22 Jul 2012 15:59:45 +0800
From:	Zheng Liu <gnehzuil.liu@...il.com>
To:	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org
Cc:	xiaoqiangnk@...il.com, achender@...ux.vnet.ibm.com,
	wenqing.lz@...bao.com
Subject: [RFC][PATCH 09/10 v1][RESEND] ext4: don't need to writeout all dirty pages in punch hole

From: Zheng Liu <wenqing.lz@...bao.com>

Now we don't need to writeout all dirty pages when punching a hole.  The i_mutex
locking is taken to avoid concurrent writes.  In truncate_pagecache_range, all
pages in this hole is released, and ext4_es_remove_space is called to update
extent status tree. 

Signed-off-by: Zheng Liu <wenqing.lz@...bao.com>
---
 fs/ext4/extents.c |   28 ++++++++++++----------------
 1 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index f2c5294..2a526b4 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4529,9 +4529,11 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 	loff_t first_page_offset, last_page_offset;
 	int credits, err = 0;
 
+	mutex_lock(&inode->i_mutex);
+
 	/* No need to punch hole beyond i_size */
 	if (offset >= inode->i_size)
-		return 0;
+		goto error;
 
 	/*
 	 * If the hole extends beyond i_size, set the hole
@@ -4549,18 +4551,6 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 	first_page_offset = first_page << PAGE_CACHE_SHIFT;
 	last_page_offset = last_page << PAGE_CACHE_SHIFT;
 
-	/*
-	 * Write out all dirty pages to avoid race conditions
-	 * Then release them.
-	 */
-	if (mapping->nrpages && mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
-		err = filemap_write_and_wait_range(mapping,
-			offset, offset + length - 1);
-
-		if (err)
-			return err;
-	}
-
 	/* Now release the pages */
 	if (last_page_offset > first_page_offset) {
 		truncate_pagecache_range(inode, first_page_offset,
@@ -4572,12 +4562,14 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 
 	credits = ext4_writepage_trans_blocks(inode);
 	handle = ext4_journal_start(inode, credits);
-	if (IS_ERR(handle))
-		return PTR_ERR(handle);
+	if (IS_ERR(handle)) {
+		err = PTR_ERR(handle);
+		goto error;
+	}
 
 	err = ext4_orphan_add(handle, inode);
 	if (err)
-		goto out;
+		goto error;
 
 	/*
 	 * Now we need to zero out the non-page-aligned data in the
@@ -4652,6 +4644,8 @@ int ext4_ext_punch_hole(struct file *file, loff_t offset, loff_t length)
 	ext4_ext_invalidate_cache(inode);
 	ext4_discard_preallocations(inode);
 
+	err = ext4_es_remove_space(inode, first_block,
+				   stop_block - first_block);
 	err = ext4_ext_remove_space(inode, first_block, stop_block - 1);
 
 	ext4_ext_invalidate_cache(inode);
@@ -4667,6 +4661,8 @@ out:
 	inode->i_mtime = inode->i_ctime = ext4_current_time(inode);
 	ext4_mark_inode_dirty(handle, inode);
 	ext4_journal_stop(handle);
+error:
+	mutex_unlock(&inode->i_mutex);
 	return err;
 }
 int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
-- 
1.7.4.1

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