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 59855df..62de921 100644 (file)
--- 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 9141944..97ad37f 100644 (file)
--- a/lib/ext2fs/closefs.c
+++ b/lib/ext2fs/closefs.c
@@ -262,6 +262,11 @@ 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;
        unsigned long   fs_state;
@@ -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
@@ -423,6 +430,11 @@ 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;
        io_stats stats = 0;
@@ -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 1b9acc3..c3237db 100644 (file)
--- a/lib/ext2fs/ext2fs.h
+++ b/lib/ext2fs/ext2fs.h
@@ -593,6 +593,12 @@ 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,