From: Richard W.M. Jones <rjones@redhat.com>
Date: Sat, 24 Sep 2011 14:50:42 +0000 (-0400)
Subject: libext2fs: add flag to ext2fs_flush() and ext2fs_close() to avoid fsync
X-Git-Tag: v1.42-WIP-0925~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9d9a53e651fa877eb4f9df0bfd97fbcc5f514293;p=thirdparty%2Fe2fsprogs.git

libext2fs: add flag to ext2fs_flush() and ext2fs_close() to avoid fsync

This adds new APIs: ext2fs_flush2 and ext2fs_close2 which take an
extra 'int flags' parameter.

This allows us to pass in an EXT2_FLAG_FLUSH_NO_SYNC flag which avoids
fsync'ing the filesystem when closing it.  For the case we have in
mind where we are just constructing a throwaway ext2 filesystem in a
file in order to boot a VM, this saves over 5 seconds during the boot
process and avoids many unnecessary disk writes.

Existing code using ext2fs_flush and ext2fs_close remains unaffected
by this change.

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
---

diff --git a/debian/e2fslibs.symbols b/debian/e2fslibs.symbols
index 59855df7c..62de921b6 100644
--- a/debian/e2fslibs.symbols
+++ b/debian/e2fslibs.symbols
@@ -105,6 +105,7 @@ libext2fs.so.2 e2fslibs #MINVER#
  ext2fs_clear_generic_bitmap@Base 1.41.0
  ext2fs_clear_generic_bmap@Base 1.41.99
  ext2fs_clear_inode_bitmap@Base 1.37
+ ext2fs_close2@Base 1.41.99
  ext2fs_close@Base 1.37
  ext2fs_close_inode_scan@Base 1.37
  ext2fs_compare_block_bitmap@Base 1.37
@@ -195,6 +196,7 @@ libext2fs.so.2 e2fslibs #MINVER#
  ext2fs_file_set_size@Base 1.37
  ext2fs_file_write@Base 1.37
  ext2fs_find_block_device@Base 1.37
+ ext2fs_flush2@Base 1.41.99
  ext2fs_flush@Base 1.37
  ext2fs_flush_icache@Base 1.37
  ext2fs_follow_link@Base 1.37
diff --git a/lib/ext2fs/closefs.c b/lib/ext2fs/closefs.c
index 9141944ea..97ad37f71 100644
--- a/lib/ext2fs/closefs.c
+++ b/lib/ext2fs/closefs.c
@@ -261,6 +261,11 @@ static errcode_t write_backup_super(ext2_filsys fs, dgrp_t group,
 }
 
 errcode_t ext2fs_flush(ext2_filsys fs)
+{
+	return ext2fs_flush2(fs, 0);
+}
+
+errcode_t ext2fs_flush2(ext2_filsys fs, int flags)
 {
 	dgrp_t		i;
 	errcode_t	retval;
@@ -402,14 +407,16 @@ write_primary_superblock_only:
 	ext2fs_swap_super(super_shadow);
 #endif
 
-	retval = io_channel_flush(fs->io);
+	if (!(flags & EXT2_FLAG_FLUSH_NO_SYNC))
+		retval = io_channel_flush(fs->io);
 	retval = write_primary_superblock(fs, super_shadow);
 	if (retval)
 		goto errout;
 
 	fs->flags &= ~EXT2_FLAG_DIRTY;
 
-	retval = io_channel_flush(fs->io);
+	if (!(flags & EXT2_FLAG_FLUSH_NO_SYNC))
+		retval = io_channel_flush(fs->io);
 errout:
 	fs->super->s_state = fs_state;
 #ifdef WORDS_BIGENDIAN
@@ -422,6 +429,11 @@ errout:
 }
 
 errcode_t ext2fs_close(ext2_filsys fs)
+{
+	return ext2fs_close2(fs, 0);
+}
+
+errcode_t ext2fs_close2(ext2_filsys fs, int flags)
 {
 	errcode_t	retval;
 	int		meta_blks;
@@ -447,7 +459,7 @@ errcode_t ext2fs_close(ext2_filsys fs)
 			fs->flags |= EXT2_FLAG_SUPER_ONLY | EXT2_FLAG_DIRTY;
 	}
 	if (fs->flags & EXT2_FLAG_DIRTY) {
-		retval = ext2fs_flush(fs);
+		retval = ext2fs_flush2(fs, flags);
 		if (retval)
 			return retval;
 	}
diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
index 1b9acc305..c3237dbf7 100644
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -592,6 +592,12 @@ typedef struct stat64 ext2fs_struct_stat;
 typedef struct stat ext2fs_struct_stat;
 #endif
 
+/*
+ * For ext2fs_close2() and ext2fs_flush2(), this flag allows you to
+ * avoid the fsync call.
+ */
+#define EXT2_FLAG_FLUSH_NO_SYNC          1
+
 /*
  * function prototypes
  */
@@ -876,7 +882,9 @@ extern errcode_t ext2fs_check_desc(ext2_filsys fs);
 
 /* closefs.c */
 extern errcode_t ext2fs_close(ext2_filsys fs);
+extern errcode_t ext2fs_close2(ext2_filsys fs, int flags);
 extern errcode_t ext2fs_flush(ext2_filsys fs);
+extern errcode_t ext2fs_flush2(ext2_filsys fs, int flags);
 extern int ext2fs_bg_has_super(ext2_filsys fs, int group_block);
 extern errcode_t ext2fs_super_and_bgd_loc2(ext2_filsys fs,
 				    dgrp_t group,