[PATCH] pg_upgrade: support for btrfs copy-on-write clones - Mailing list pgsql-hackers

Add file cloning as an alternative data transfer method to pg_upgrade.
Currently only btrfs is supported, but copy-on-write cloning is also
available on at least ZFS.  Cloning must be requested explicitly and if
it isn't supported by the operating system or filesystem a fatal error
is thrown.

This provides upgrade performance similar to link mode while allowing
the old cluster to be used even after the new one has been started.

Signed-off-by: Oskari Saarenmaa <os@ohmu.fi>
---configure                        |   5 +-configure.in                     |   7 ++-contrib/pg_upgrade/check.c
|  3 +contrib/pg_upgrade/file.c        | 125 +++++++++++++++++++++++++++++----------contrib/pg_upgrade/option.c      |
7 +++contrib/pg_upgrade/pg_upgrade.h  |  13 ++--contrib/pg_upgrade/relfilenode.c |  31
++++------doc/src/sgml/pgupgrade.sgml     |   7 +++src/include/pg_config.h.in       |   3 +9 files changed, 141
insertions(+),60 deletions(-)
 

diff --git a/configure b/configure
index c685ca3..5087463 100755
--- a/configure
+++ b/configure
@@ -10351,7 +10351,10 @@ done
-for ac_header in crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h poll.h pwd.h sys/ioctl.h sys/ipc.h
sys/poll.hsys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h sys/tas.h sys/time.h
sys/un.htermios.h ucred.h utime.h wchar.h wctype.h
 
+for ac_header in crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h \
+    linux/btrfs.h poll.h pwd.h sys/ioctl.h sys/ipc.h sys/poll.h sys/pstat.h \
+    sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h \
+    sys/tas.h sys/time.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.hdoas_ac_Header=`$as_echo
"ac_cv_header_$ac_header"| $as_tr_sh`if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
 
diff --git a/configure.in b/configure.in
index 82771bd..609aa73 100644
--- a/configure.in
+++ b/configure.in
@@ -982,7 +982,12 @@ AC_SUBST(OSSP_UUID_LIBS)##dnl sys/socket.h is required by AC_FUNC_ACCEPT_ARGTYPES
-AC_CHECK_HEADERS([crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h poll.h pwd.h sys/ioctl.h sys/ipc.h
sys/poll.hsys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h sys/tas.h sys/time.h
sys/un.htermios.h ucred.h utime.h wchar.h wctype.h])
 
+AC_CHECK_HEADERS([crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h \
+                  langinfo.h linux/btrfs.h poll.h pwd.h sys/ioctl.h \
+                  sys/ipc.h sys/poll.h sys/pstat.h sys/resource.h \
+                  sys/select.h sys/sem.h sys/shm.h sys/socket.h \
+                  sys/sockio.h sys/tas.h sys/time.h sys/un.h termios.h \
+                  ucred.h utime.h wchar.h wctype.h])# On BSD, test for net/if.h will fail unless sys/socket.h# is
includedfirst.
 
diff --git a/contrib/pg_upgrade/check.c b/contrib/pg_upgrade/check.c
index 0376fcb..2a52dd8 100644
--- a/contrib/pg_upgrade/check.c
+++ b/contrib/pg_upgrade/check.c
@@ -151,6 +151,9 @@ check_new_cluster(void)    if (user_opts.transfer_mode == TRANSFER_MODE_LINK)
check_hard_link();
+    if (user_opts.transfer_mode == TRANSFER_MODE_CLONE)
+        check_clone_file();
+    check_is_super_user(&new_cluster);    /*
diff --git a/contrib/pg_upgrade/file.c b/contrib/pg_upgrade/file.c
index dfeb79f..fc935b7 100644
--- a/contrib/pg_upgrade/file.c
+++ b/contrib/pg_upgrade/file.c
@@ -8,11 +8,16 @@ */#include "postgres_fe.h"
+#include "pg_config.h"#include "pg_upgrade.h"#include <fcntl.h>
+#ifdef HAVE_LINUX_BTRFS_H
+# include <sys/ioctl.h>
+# include <linux/btrfs.h>
+#endif#ifndef WIN32
@@ -23,21 +28,42 @@ static int    win32_pghardlink(const char *src, const char *dst);/*
- * copyAndUpdateFile()
+ * upgradeFile() *
- *    Copies a relation file from src to dst.  If pageConverter is non-NULL, this function
- *    uses that pageConverter to do a page-by-page conversion.
+ * Transfer a relation file from src to dst using one of the supported
+ * methods.  If the on-disk format of the new cluster is bit-for-bit
+ * compatible with the on-disk format of the old cluster we can simply link
+ * each relation to perform a true in-place upgrade.  Otherwise we must copy
+ * (either block-by-block or using a copy-on-write clone) the data from old
+ * cluster to new cluster and then perform the conversion. */const char *
-copyAndUpdateFile(pageCnvCtx *pageConverter,
-                  const char *src, const char *dst, bool force)
+upgradeFile(transferMode transfer_mode, const char *src,
+        const char *dst, pageCnvCtx *pageConverter){    if (pageConverter == NULL)    {
-        if (pg_copy_file(src, dst, force) == -1)
-            return getErrorText(errno);
-        else
-            return NULL;
+        int rc = -1;
+
+        switch (transfer_mode)
+        {
+            case TRANSFER_MODE_COPY:
+                rc = pg_copy_file(src, dst, true);
+                break;
+            case TRANSFER_MODE_CLONE:
+                rc = upg_clone_file(src, dst);
+                break;
+            case TRANSFER_MODE_LINK:
+                rc = pg_link_file(src, dst);
+                break;
+        }
+
+        return (rc < 0) ? getErrorText(errno) : NULL;
+    }
+    else if (transfer_mode != TRANSFER_MODE_COPY)
+    {
+        return "Cannot in-place update this cluster, "
+            "page-by-page (copy-mode) conversion is required";    }    else    {
@@ -100,29 +126,6 @@ copyAndUpdateFile(pageCnvCtx *pageConverter,}
-/*
- * linkAndUpdateFile()
- *
- * Creates a hard link between the given relation files. We use
- * this function to perform a true in-place update. If the on-disk
- * format of the new cluster is bit-for-bit compatible with the on-disk
- * format of the old cluster, we can simply link each relation
- * instead of copying the data from the old cluster to the new cluster.
- */
-const char *
-linkAndUpdateFile(pageCnvCtx *pageConverter,
-                  const char *src, const char *dst)
-{
-    if (pageConverter != NULL)
-        return "Cannot in-place update this cluster, page-by-page conversion is required";
-
-    if (pg_link_file(src, dst) == -1)
-        return getErrorText(errno);
-    else
-        return NULL;
-}
-
-#ifndef WIN32static intcopy_file(const char *srcfile, const char *dstfile, bool force)
@@ -228,6 +231,64 @@ win32_pghardlink(const char *src, const char *dst)#endif
+int
+upg_clone_file(const char *existing_file, const char *new_file)
+{
+#ifdef BTRFS_IOC_CLONE
+    int rc, res_errno = 0, src_fd = -1, dest_fd = -1;
+
+    src_fd = open(existing_file, O_RDONLY);
+    if (src_fd < 0)
+        return -1;
+
+    dest_fd = open(new_file, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+    if (dest_fd < 0)
+    {
+        close(src_fd);
+        return -1;
+    }
+
+    rc = ioctl(dest_fd, BTRFS_IOC_CLONE, src_fd);
+    if (rc < 0)
+    {
+        pg_log(PG_REPORT, "btrfs clone: %s\n", strerror(errno));
+        res_errno = errno;  /* save errno for caller */
+        unlink(new_file);
+    }
+
+    close(dest_fd);
+    close(src_fd);
+
+    errno = res_errno;  /* restore errno after close() calls */
+    return rc;
+#else
+    /* TODO: add support for zfs clones */
+    pg_log(PG_REPORT, "system does not support file cloning\n");
+    errno = ENOSYS;
+    return -1;
+#endif
+}
+
+void
+check_clone_file(void)
+{
+    char        existing_file[MAXPGPATH];
+    char        cloned_file[MAXPGPATH];
+
+    snprintf(existing_file, sizeof(existing_file), "%s/PG_VERSION", old_cluster.pgdata);
+    snprintf(cloned_file, sizeof(cloned_file), "%s/PG_VERSION.linktest", new_cluster.pgdata);
+    unlink(cloned_file);        /* might fail */
+
+    if (upg_clone_file(existing_file, cloned_file) == -1)
+    {
+        pg_log(PG_FATAL,
+               "Could not clone a file between old and new data directories: %s\n"
+               "File cloning is currently only supported on btrfs.\n",
+               getErrorText(errno));
+    }
+    unlink(cloned_file);
+}
+/* fopen() file with no group/other permissions */FILE *fopen_priv(const char *path, const char *mode)
diff --git a/contrib/pg_upgrade/option.c b/contrib/pg_upgrade/option.c
index 2774b1e..fdf9f5c 100644
--- a/contrib/pg_upgrade/option.c
+++ b/contrib/pg_upgrade/option.c
@@ -54,6 +54,7 @@ parseCommandLine(int argc, char *argv[])        {"retain", no_argument, NULL, 'r'},        {"jobs",
required_argument,NULL, 'j'},        {"verbose", no_argument, NULL, 'v'},
 
+        {"clone", no_argument, NULL, 1},        {NULL, 0, NULL, 0}    };    int            option;            /*
Commandline option */
 
@@ -186,6 +187,10 @@ parseCommandLine(int argc, char *argv[])                log_opts.verbose = true;
break;
+            case 1:
+                user_opts.transfer_mode = TRANSFER_MODE_CLONE;
+                break;
+            default:                pg_log(PG_FATAL,                       "Try \"%s --help\" for more
information.\n",
@@ -236,6 +241,8 @@ Options:\n\  -D, --new-datadir=DATADIR     new cluster data directory\n\  -j, --jobs
   number of simultaneous processes or threads to use\n\  -k, --link                    link instead of copying files
tonew cluster\n\
 
+      --clone                   use copy-on-write cloning instead of copying\n\
+                                files to new cluster (only supported on btrfs)\n\  -o, --old-options=OPTIONS     old
clusteroptions to pass to the server\n\  -O, --new-options=OPTIONS     new cluster options to pass to the server\n\
-p,--old-port=PORT           old cluster port number (default %d)\n\
 
diff --git a/contrib/pg_upgrade/pg_upgrade.h b/contrib/pg_upgrade/pg_upgrade.h
index 0b3ad20..6932bd6 100644
--- a/contrib/pg_upgrade/pg_upgrade.h
+++ b/contrib/pg_upgrade/pg_upgrade.h
@@ -209,12 +209,13 @@ typedef struct} ControlData;/*
- * Enumeration to denote link modes
+ * Enumeration to denote transfer mode */typedef enum{    TRANSFER_MODE_COPY,
-    TRANSFER_MODE_LINK
+    TRANSFER_MODE_LINK,
+    TRANSFER_MODE_CLONE} transferMode;/*
@@ -381,12 +382,12 @@ const pageCnvCtx *setupPageConverter(void);typedef void *pageCnvCtx;#endif
-const char *copyAndUpdateFile(pageCnvCtx *pageConverter, const char *src,
-                  const char *dst, bool force);
-const char *linkAndUpdateFile(pageCnvCtx *pageConverter, const char *src,
-                  const char *dst);
+const char *upgradeFile(transferMode transfer_mode, const char *src,
+                const char *dst, pageCnvCtx *pageConverter);void        check_hard_link(void);
+void        check_clone_file(void);
+int        upg_clone_file(const char *old_file, const char *new_file);FILE       *fopen_priv(const char *path, const
char*mode);/* function.c */
 
diff --git a/contrib/pg_upgrade/relfilenode.c b/contrib/pg_upgrade/relfilenode.c
index a951fc9..c808313 100644
--- a/contrib/pg_upgrade/relfilenode.c
+++ b/contrib/pg_upgrade/relfilenode.c
@@ -32,7 +32,10 @@ transfer_all_new_tablespaces(DbInfoArr *old_db_arr, DbInfoArr *new_db_arr,
 char *old_pgdata, char *new_pgdata){    pg_log(PG_REPORT, "%s user relation files\n",
 
-      user_opts.transfer_mode == TRANSFER_MODE_LINK ? "Linking" : "Copying");
+        user_opts.transfer_mode == TRANSFER_MODE_COPY ? "Copying" :
+        user_opts.transfer_mode == TRANSFER_MODE_LINK ? "Linking" :
+        user_opts.transfer_mode == TRANSFER_MODE_CLONE ? "Cloning" :
+        "FAIL");    /*     * Transfering files by tablespace is tricky because a single database can
@@ -270,26 +273,14 @@ transfer_relfile(pageCnvCtx *pageConverter, FileNameMap *map,        /* Copying files might take
sometime, so give feedback. */        pg_log(PG_STATUS, "%s", old_file);
 
-        if ((user_opts.transfer_mode == TRANSFER_MODE_LINK) && (pageConverter != NULL))
-            pg_log(PG_FATAL, "This upgrade requires page-by-page conversion, "
-                   "you must use copy mode instead of link mode.\n");
-
-        if (user_opts.transfer_mode == TRANSFER_MODE_COPY)
-        {
-            pg_log(PG_VERBOSE, "copying \"%s\" to \"%s\"\n", old_file, new_file);
-
-            if ((msg = copyAndUpdateFile(pageConverter, old_file, new_file, true)) != NULL)
-                pg_log(PG_FATAL, "error while copying relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
-                       map->nspname, map->relname, old_file, new_file, msg);
-        }
-        else
+        msg = upgradeFile(user_opts.transfer_mode, old_file, new_file, pageConverter);
+        if (msg != NULL)        {
-            pg_log(PG_VERBOSE, "linking \"%s\" to \"%s\"\n", old_file, new_file);
-
-            if ((msg = linkAndUpdateFile(pageConverter, old_file, new_file)) != NULL)
-                pg_log(PG_FATAL,
-                       "error while creating link for relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
-                       map->nspname, map->relname, old_file, new_file, msg);
+            pg_log(PG_FATAL, "error while %s relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
+                (user_opts.transfer_mode == TRANSFER_MODE_COPY ? "copying" :
+                 user_opts.transfer_mode == TRANSFER_MODE_LINK ? "linking" :
+                 user_opts.transfer_mode == TRANSFER_MODE_CLONE ? "cloning" :
+                 "FAIL"), map->nspname, map->relname, old_file, new_file, msg);        }    }
diff --git a/doc/src/sgml/pgupgrade.sgml b/doc/src/sgml/pgupgrade.sgml
index f6cd9f0..fc9b89d 100644
--- a/doc/src/sgml/pgupgrade.sgml
+++ b/doc/src/sgml/pgupgrade.sgml
@@ -126,6 +126,13 @@     </varlistentry>     <varlistentry>
+      <term><option>--clone</option></term>
+      <listitem><para>use copy-on-write clones instead of copying or hard linking files to
+      the new cluster; this option can only be used when the old and new clusters reside
+      on the same btrfs filesystem</para></listitem>
+     </varlistentry>
+
+     <varlistentry>      <term><option>-o</option> <replaceable class="parameter">options</replaceable></term>
<term><option>--old-options</option><replaceable class="parameter">options</replaceable></term>
<listitem><para>optionsto be passed directly to the
 
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 8aabf3c..7cd5a8d 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -317,6 +317,9 @@/* Define to 1 if you have the `z' library (-lz). */#undef HAVE_LIBZ
+/* Define to 1 if you have the <linux/btrfs.h> header file. */
+#undef HAVE_LINUX_BTRFS_H
+/* Define to 1 if constants of type 'long long int' should have the suffix LL.   */#undef HAVE_LL_CONSTANTS
-- 
1.8.3.1