On Mon, Jan 08, 2007 at 07:58:19AM -0500, Theodore Tso wrote:
> On Mon, Jan 08, 2007 at 08:35:55AM +0530, Suparna Bhattacharya wrote:
> > > Yeah, slowly-growing directories will get splattered all over the disk.
> > >
> > > Possible short-term fixes would be to just allocate up to (say) eight
> > > blocks when we grow a directory by one block. Or teach the
> > > directory-growth code to use ext3 reservations.
> > >
> > > Longer-term people are talking about things like on-disk rerservations.
> > > But I expect directories are being forgotten about in all of that.
> >
> > By on-disk reservations, do you mean persistent file preallocation ? (that
> > is explicit preallocation of blocks to a given file) If so, you are
> > right, we haven't really given any thought to the possibility of directories
> > needing that feature.
>
> The fastest and probably most important thing to add is some readahead
> smarts to directories --- both to the htree and non-htree cases. If
Here's is a quick hack to practice the directory readahead idea.
Comments are welcome, it's a freshman's work :)
Regards,
Wu
---
fs/ext3/dir.c | 22 ++++++++++++++++++++++
fs/ext3/inode.c | 2 +-
2 files changed, 23 insertions(+), 1 deletion(-)
--- linux.orig/fs/ext3/dir.c
+++ linux/fs/ext3/dir.c
@@ -94,6 +94,25 @@ int ext3_check_dir_entry (const char * f
return error_msg == NULL ? 1 : 0;
}
+int ext3_get_block(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int create);
+
+static void ext3_dir_readahead(struct file * filp)
+{
+ struct inode *inode = filp->f_path.dentry->d_inode;
+ struct address_space *mapping = inode->i_sb->s_bdev->bd_inode->i_mapping;
+ unsigned long sector;
+ unsigned long blk;
+ pgoff_t offset;
+
+ for (blk = 0; blk < inode->i_blocks; blk++) {
+ sector = blk << (inode->i_blkbits - 9);
+ sector = generic_block_bmap(inode->i_mapping, sector, ext3_get_block);
+ offset = sector >> (PAGE_CACHE_SHIFT - 9);
+ do_page_cache_readahead(mapping, filp, offset, 1);
+ }
+}
+
static int ext3_readdir(struct file * filp,
void * dirent, filldir_t filldir)
{
@@ -108,6 +127,9 @@ static int ext3_readdir(struct file * fi
sb = inode->i_sb;
+ if (!filp->f_pos)
+ ext3_dir_readahead(filp);
+
#ifdef CONFIG_EXT3_INDEX
if (EXT3_HAS_COMPAT_FEATURE(inode->i_sb,
EXT3_FEATURE_COMPAT_DIR_INDEX) &&
--- linux.orig/fs/ext3/inode.c
+++ linux/fs/ext3/inode.c
@@ -945,7 +945,7 @@ out:
#define DIO_CREDITS (EXT3_RESERVE_TRANS_BLOCKS + 32)
-static int ext3_get_block(struct inode *inode, sector_t iblock,
+int ext3_get_block(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
handle_t *handle = journal_current_handle();
-
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