xapcmd: avoid EXDEV when finalizing changes

By creating temporary directories as deep as possible,
we can allow v2 repositories to have `xap$SCHEMA_VERSION'
(e.g. `xap15') reside on a separate FS.

We also check st_dev ahead-of-time to avoid doing work which
will fail with EXDEV.  Of course, another process may still
move/change things around.

diff --git a/lib/PublicInbox/Xapcmd.pm b/lib/PublicInbox/Xapcmd.pm
index 697221d9a8e3c0f9b7cdcb0c135bf6e7cebd9e4f..860f90aa512acc1e35e09c3a7f38393b70fad5c3 100644 (file)
--- a/lib/PublicInbox/Xapcmd.pm
+++ b/lib/PublicInbox/Xapcmd.pm
@@ -8,31 +8,36 @@ use PublicInbox::Over;
 use PublicInbox::Search;
 use File::Temp qw(tempdir);
 use File::Path qw(remove_tree);
+use File::Basename qw(dirname);
 
 # support testing with dev versions of Xapian which installs
 # commands with a version number suffix (e.g. "xapian-compact-1.5")
 our $XAPIAN_COMPACT = $ENV{XAPIAN_COMPACT} || 'xapian-compact';
 
-sub commit_changes ($$$$) {
-       my ($ibx, $old, $new, $opt) = @_;
+sub commit_changes ($$$) {
+       my ($ibx, $tmp, $opt) = @_;
 
        my $reindex = $opt->{reindex};
        my $im = $ibx->importer(0);
        $im->lock_acquire if $reindex;
 
-       my @st = stat($old) or die "failed to stat($old): $!\n";
+       while (my ($old, $new) = each %$tmp) {
+               my @st = stat($old) or die "failed to stat($old): $!\n";
 
-       my $over = "$old/over.sqlite3";
-       if (-f $over) {
-               $over = PublicInbox::Over->new($over);
-               $over->connect->sqlite_backup_to_file("$new/over.sqlite3");
-               $over = undef;
-       }
-       rename($old, "$new/old") or die "rename $old => $new/old: $!\n";
-       chmod($st[2] & 07777, $new) or die "chmod $old: $!\n";
-       rename($new, $old) or die "rename $new => $old: $!\n";
-       remove_tree("$old/old") or die "failed to remove $old/old: $!\n";
+               my $over = "$old/over.sqlite3";
+               if (-f $over) { # only for v1, v2 over is untouched
+                       $over = PublicInbox::Over->new($over);
+                       my $tmp_over = "$new/over.sqlite3";
+                       $over->connect->sqlite_backup_to_file($tmp_over);
+                       $over = undef;
+               }
 
+               rename($old, "$new/old") or die "rename $old => $new/old: $!\n";
+               chmod($st[2] & 07777, $new) or die "chmod $old: $!\n";
+               rename($new, $old) or die "rename $new => $old: $!\n";
+               my $prev = "$old/old";
+               remove_tree($prev) or die "failed to remove $prev: $!\n";
+       }
        if ($reindex) {
                $opt->{-skip_lock} = 1;
                PublicInbox::Admin::index_inbox($ibx, $opt);
@@ -94,19 +99,23 @@ sub progress_prepare ($) {
        }
 }
 
+sub same_fs_or_die ($$) {
+       my ($x, $y) = @_;
+       return if ((stat($x))[0] == (stat($y))[0]); # 0 - st_dev
+       die "$x and $y reside on different filesystems\n";
+}
+
 sub run {
        my ($ibx, $cmd, $env, $opt) = @_;
        progress_prepare($opt ||= {});
        my $dir = $ibx->{mainrepo} or die "no mainrepo in inbox\n";
        my $exe = $cmd->[0];
-       my $pfx = $exe;
        runnable_or_die($XAPIAN_COMPACT) if $opt->{compact};
 
        my $reindex; # v1:{ from => $x40 }, v2:{ from => [ $x40, $x40, .. ] } }
        my $from; # per-epoch ranges
 
        if (ref($exe) eq 'CODE') {
-               $pfx = 'CODE';
                $reindex = $opt->{reindex} = {};
                $from = $reindex->{from} = [];
                require Search::Xapian::WritableDatabase;
@@ -116,16 +125,28 @@ sub run {
        $ibx->umask_prepare;
        my $old = $ibx->search->xdir(1);
        -d $old or die "$old does not exist\n";
-       my $new = tempdir("$pfx-XXXXXXXX", DIR => $dir);
+
+       my $tmp = {}; # old partition => new (tmp) partition
        my $v = $ibx->{version} ||= 1;
        my @cmds;
+
+       # we want temporary directories to be as deep as possible,
+       # so v2 partitions can keep "xap$SCHEMA_VERSION" on a separate FS.
        if ($v == 1) {
-               push @cmds, [@$cmd, $old, $new];
+               my $old_parent = dirname($old);
+               same_fs_or_die($old_parent, $old);
+               $tmp->{$old} = tempdir('xapcmd-XXXXXXXX', DIR => $old_parent);
+               push @cmds, [ @$cmd, $old, $tmp->{$old} ];
        } else {
                opendir my $dh, $old or die "Failed to opendir $old: $!\n";
                while (defined(my $dn = readdir($dh))) {
                        if ($dn =~ /\A\d+\z/) {
-                               push @cmds, [@$cmd, "$old/$dn", "$new/$dn"];
+                               my $tmpl = "$dn-XXXXXXXX";
+                               my $dst = tempdir($tmpl, DIR => $old);
+                               same_fs_or_die($old, $dst);
+                               my $cur = "$old/$dn";
+                               push @cmds, [@$cmd, $cur, $dst ];
+                               $tmp->{$cur} = $dst;
                        } elsif ($dn eq '.' || $dn eq '..') {
                        } elsif ($dn =~ /\Aover\.sqlite3/) {
                        } else {
@@ -158,7 +179,7 @@ sub run {
                                die join(' ', @$x)." failed: $?\n" if $?;
                        }
                }
-               commit_changes($ibx, $old, $new, $opt);
+               commit_changes($ibx, $tmp, $opt);
        });
 }