LU-9160 libext2: readahead for meta_bg

There are ~37k random IOs with meta_bg option on a 300T target.
It takes something like 20min to finish a simple debugfs start.
Enabling RA for meta blocks saves time dramatically and it
needs just 12s to start debugfs.

Seagate-bug-id: MRP-4159
Change-Id: I6ed500d2068b16c1a5ff3fd281ae88bcbb780bf2
Signed-off-by: Alexey Lyashkov <alexey.lyashkov@seagate.com>
Reviewed-on: https://review.whamcloud.com/25648
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>

diff --git a/lib/ext2fs/openfs.c b/lib/ext2fs/openfs.c
index ba501e6..95f06a0 100644 (file)
--- a/lib/ext2fs/openfs.c
+++ b/lib/ext2fs/openfs.c
@@ -392,20 +392,26 @@ errcode_t ext2fs_open2(const char *name, const char *io_options,
                        goto cleanup;
 #ifdef WORDS_BIGENDIAN
                gdp = (struct ext2_group_desc *) dest;
-               for (j=0; j < groups_per_block*first_meta_bg; j++) {
+               for (j = 0; j < groups_per_block * first_meta_bg; j++) {
                        gdp = ext2fs_group_desc(fs, fs->group_desc, j);
                        ext2fs_swap_group_desc2(fs, gdp);
                }
 #endif
                dest += fs->blocksize*first_meta_bg;
        }
-       for (i=first_meta_bg ; i < fs->desc_blocks; i++) {
+
+       for (i = first_meta_bg; i < fs->desc_blocks; i++) {
+               blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
+               io_channel_cache_readahead(fs->io, blk, 1);
+       }
+
+       for (i = first_meta_bg; i < fs->desc_blocks; i++) {
                blk = ext2fs_descriptor_block_loc2(fs, group_block, i);
                retval = io_channel_read_blk64(fs->io, blk, 1, dest);
                if (retval)
                        goto cleanup;
 #ifdef WORDS_BIGENDIAN
-               for (j=0; j < groups_per_block; j++) {
+               for (j = 0; j < groups_per_block; j++) {
                        gdp = ext2fs_group_desc(fs, fs->group_desc,
                                                i * groups_per_block + j);
                        ext2fs_swap_group_desc2(fs, gdp);