dm6: finish WIP

diff --git a/dm6 b/dm6
index c5ce5d45ee6ec6e0760df40589bef258d3ca1e54..b7a9cdf57f9beb1318bd2aab794e21ead1310362 100755 (executable)
--- a/dm6
+++ b/dm6
@@ -6,6 +6,7 @@ use Fcntl qw(:DEFAULT :flock);
 use File::Compare;
 use File::Path;
 use File::Temp;
+use File::stat;
 
 # Copyright (C) 2010 Zygo Blaxell <dm5@mailtoo.hungrycats.org>
 
@@ -45,6 +46,7 @@ USAGE
 sub link_files {
        my ($from, $to) = (@_);
 
+       print STDERR "link '$from' '$to' ...";
        my $inode_dir = $to;
        my $inode_base = $to;
        $inode_dir =~ s:[^/]*$::o;
@@ -56,26 +58,106 @@ sub link_files {
                unlink($tmp_to) or warn "unlink: $tmp_to: $!";  # Try, possibly in vain, to clean up
                die "rename: $tmp_to -> $from: $saved_bang";
        }
+       print STDERR "\n";
 }
 
 my $link_dir = shift @ARGV;
 (-d $link_dir) or usage;
 
+sub slash_prefix {
+       my ($file) = @_;
+       my $prefix = substr($file, 0, 3);
+       my $suffix = substr($file, 3);
+       $prefix =~ s:(.):$1/:osg;
+       chop($prefix);
+       return ($prefix, $suffix);
+}
+
+sub prepare_parents {
+       my ($link_dir, $file) = @_;
+       my ($prefix, $suffix) = slash_prefix($file);
+       my $parent = "$link_dir/$prefix";
+       mkpath($parent, { verbose => 1 });
+       die "mkpath: $parent: $!" unless -d $parent;
+       return "$parent/$prefix/$suffix";
+}
+
+# ext3 cannot handle more than 32000 links to a file.  Leave some headroom.
+my $link_count_max = 31990;
+
 $/ = "\0";
 while (<STDIN>) {
        my $file = $_;
        eval {
-               chomp $file;
-               print STDERR "digest($file) = ";
-               my $digest = digest($file);
-               $digest =~ y:/:_:;
-               print STDERR "$digest\n";
-               $digest =~ s:^(.)(.)(.):$1/$2/$3:osg;
-               my ($parent) = ($digest =~ m:^(.*/):osg);
-               $parent = "$link_dir/$parent";
-               mkpath($parent, { verbose => 1 });
-               die "mkpath: $parent: $!" unless -d $parent;
-               link_files($file, "$link_dir/$digest");
+               for (1) {
+                       chomp $file;
+
+                       # Get file stat data
+                       my $st = lstat($file);
+                       die "lstat: $file: $!" unless $st;
+
+                       # Oops?
+                       next unless -f _;
+
+                       # Skip the file if it has far too many links already
+                       next if ($st->nlink > $link_count_max);
+
+                       # Check link to inode
+                       my $inode_link = prepare_parents("$link_dir/inode", $st->ino);
+                       my $inode_st = lstat($inode_link);
+                       my $update_links;
+                       if ($inode_st) {
+                               my $inode_dev = $inode_st->dev;
+                               my $inode_ino = $inode_st->ino;
+                               my $file_dev = $st->dev;
+                               my $file_ino = $st->ino;
+                               if ($inode_ino != $file_ino || $inode_dev != $file_dev) {
+                                       warn "inode link '$inode_link' is wrong (inode $inode_ino should be $file_ino)" if $inode_ino != $file_ino;
+                                       warn "inode link '$inode_link' is wrong (dev $inode_dev should be $file_dev)" if $inode_dev != $file_dev;
+                                       $update_links = 1;
+                               }
+                       } else {
+                               $update_links = 1;
+                       }
+
+                       # If neither criteria for updating link is met, leave it as-is
+                       next unless $update_links;
+
+                       # Compute digest
+                       print STDERR "digest($file) = ";
+                       my $digest = digest($file);
+
+                       # Base64 uses /, we prefer _
+                       $digest =~ y:/:_:;
+
+                       print STDERR "$digest\n";
+
+                       # Check link to digest
+                       my $digest_link = prepare_parents("$link_dir/digest", $digest);
+                       my $digest_st = lstat($digest_link);
+                       if ($digest_st) {
+                               my $digest_nlink = $digest_st->nlink;
+                               if ($digest_nlink > 31990) {
+                                       print STDERR "Removing '$digest_link' with $digest_nlink links\n";
+                                       unlink($digest_link) or die "unlink: $digest_link: $!";
+                                       undef $digest_st;
+                               }
+                       }
+
+                       # If digest link exists, link it to file
+                       if ($digest_st) {
+                               print STDERR "cmp '$digest_link' '$file' ...";
+                               die "NOT identical!" if compare($digest_link, $file);
+                               print STDERR "\n";
+                               link_files($digest_link, $file);
+                       } else {
+                               link_files($file, $digest_link);
+                       }
+
+                       # A link to the inode indicates we are done, so do it last
+                       link_files($file, $inode_link);
+
+               }
        };
        warn "$file: $@" if $@;
 }