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Use mount-options instead of mount to avoid implicit -o sync.

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guestfs_mount adds -o sync implicitly.  This causes a very large
performance problem for write-intensive programs (eg. virt-v2v).

Document this as a "gotcha".

Change the tests, guestfish, Sys::Guestfs::Lib, guestmount to use
mount-options instead.

(Note that this gotcha does not affect mount-ro).

The source of the performance problem was first identified by
Matthew Booth.
This commit is contained in:
Richard Jones
2010-02-09 18:00:24 +00:00
parent 245ac56737
commit f93cbe5756
11 changed files with 47 additions and 32 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
fish/fish.c
View File

@@ -474,10 +474,13 @@ mount_mps (struct mp *mp)
if (mp) {
mount_mps (mp->next);
if (!read_only)
r = guestfs_mount (g, mp->device, mp->mountpoint);
else
r = guestfs_mount_ro (g, mp->device, mp->mountpoint);
/* Don't use guestfs_mount here because that will default to mount
* options -o sync,noatime. For more information, see guestfs(3)
* section "LIBGUESTFS GOTCHAS".
*/
const char *options = read_only ? "ro" : "";
r = guestfs_mount_options (g, options, mp->device, mp->mountpoint);
if (r == -1)
exit (EXIT_FAILURE);
}

11
fuse/guestmount.c
View File

@@ -1160,10 +1160,13 @@ mount_mps (struct mp *mp)
if (mp) {
mount_mps (mp->next);
if (!read_only)
r = guestfs_mount (g, mp->device, mp->mountpoint);
else
r = guestfs_mount_ro (g, mp->device, mp->mountpoint);
/* Don't use guestfs_mount here because that will default to mount
* options -o sync,noatime. For more information, see guestfs(3)
* section "LIBGUESTFS GOTCHAS".
*/
const char *options = read_only ? "ro" : "";
r = guestfs_mount_options (g, options, mp->device, mp->mountpoint);
if (r == -1)
exit (EXIT_FAILURE);
}

2
perl/lib/Sys/Guestfs/Lib.pm
View File

@@ -1282,7 +1282,7 @@ sub mount_operating_system
if($ro) {
$g->mount_ro ($mounts->{$_}, $_)
} else {
$g->mount ($mounts->{$_}, $_)
$g->mount_options ("", $mounts->{$_}, $_)
}
}
}

2
perl/t/060-readdir.t
View File

@@ -38,7 +38,7 @@ $h->part_disk ("/dev/sda", "mbr");
ok (1);
$h->mkfs ("ext2", "/dev/sda1");
ok (1);
$h->mount ("/dev/sda1", "/");
$h->mount_options ("", "/dev/sda1", "/");
ok (1);
$h->mkdir ("/p");
ok (1);

2
regressions/rhbz503169c10.sh
View File

@@ -28,7 +28,7 @@ dd if=/dev/zero of=test1.img bs=1024k count=10
launch
part-disk /dev/sda mbr
mkfs ext2 /dev/sda1
mount /dev/sda1 /
mount-options "" /dev/sda1 /
ll /../dev/console
ll /../dev/full
ll /../dev/mapper/

2
regressions/rhbz503169c13.sh
View File

@@ -33,7 +33,7 @@ dd if=/dev/zero of=test1.img bs=1024k count=10
run
part-disk /dev/sda mbr
mkfs ext2 /dev/sda1
mount /dev/sda1 /
mount-options "" /dev/sda1 /
mkdir /dev
-command /ignore-this-error
unmount-all

2
regressions/test-cancellation-upload-daemoncancels.sh
View File

@@ -30,7 +30,7 @@ run
part-disk /dev/sda mbr
mkfs ext2 /dev/sda1
mount /dev/sda1 /
mount-options "" /dev/sda1 /
# Upload image, daemon should cancel because the image is too large
# to upload into itself.

2
regressions/test-remote.sh
View File

@@ -28,7 +28,7 @@ eval `../fish/guestfish --listen`
../fish/guestfish --remote run
../fish/guestfish --remote part-disk /dev/sda mbr
../fish/guestfish --remote mkfs ext2 /dev/sda1
../fish/guestfish --remote mount /dev/sda1 /
../fish/guestfish --remote mount-options "" /dev/sda1 /
# Failure of the above commands will cause the guestfish listener to exit.
# Incorrect return from echo_daemon will not, so need to ensure the listener

34
src/generator.ml
View File

@@ -1432,7 +1432,7 @@ on the volume group C<volgroup>, with C<size> megabytes.");
[InitEmpty, Always, TestOutput (
[["part_disk"; "/dev/sda"; "mbr"];
["mkfs"; "ext2"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["write_file"; "/new"; "new file contents"; "0"];
["cat"; "/new"]], "new file contents")],
"make a filesystem",
@@ -1508,12 +1508,12 @@ use C<guestfs_upload>.");
[InitEmpty, Always, TestOutputListOfDevices (
[["part_disk"; "/dev/sda"; "mbr"];
["mkfs"; "ext2"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["mounts"]], ["/dev/sda1"]);
InitEmpty, Always, TestOutputList (
[["part_disk"; "/dev/sda"; "mbr"];
["mkfs"; "ext2"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["umount"; "/"];
["mounts"]], [])],
"unmount a filesystem",
@@ -1544,11 +1544,11 @@ See also: C<guestfs_mountpoints>");
["mkfs"; "ext2"; "/dev/sda1"];
["mkfs"; "ext2"; "/dev/sda2"];
["mkfs"; "ext2"; "/dev/sda3"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["mkdir"; "/mp1"];
["mount"; "/dev/sda2"; "/mp1"];
["mount_options"; ""; "/dev/sda2"; "/mp1"];
["mkdir"; "/mp1/mp2"];
["mount"; "/dev/sda3"; "/mp1/mp2"];
["mount_options"; ""; "/dev/sda3"; "/mp1/mp2"];
["mkdir"; "/mp1/mp2/mp3"];
["umount_all"];
["mounts"]], [])],
@@ -2405,11 +2405,11 @@ the human-readable, canonical hex dump of the file.");
[InitNone, Always, TestOutput (
[["part_disk"; "/dev/sda"; "mbr"];
["mkfs"; "ext3"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["write_file"; "/new"; "test file"; "0"];
["umount"; "/dev/sda1"];
["zerofree"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["cat"; "/new"]], "test file")],
"zero unused inodes and disk blocks on ext2/3 filesystem",
"\
@@ -2510,13 +2510,13 @@ are activated or deactivated.");
["vgcreate"; "VG"; "/dev/sda1"];
["lvcreate"; "LV"; "VG"; "10"];
["mkfs"; "ext2"; "/dev/VG/LV"];
["mount"; "/dev/VG/LV"; "/"];
["mount_options"; ""; "/dev/VG/LV"; "/"];
["write_file"; "/new"; "test content"; "0"];
["umount"; "/"];
["lvresize"; "/dev/VG/LV"; "20"];
["e2fsck_f"; "/dev/VG/LV"];
["resize2fs"; "/dev/VG/LV"];
["mount"; "/dev/VG/LV"; "/"];
["mount_options"; ""; "/dev/VG/LV"; "/"];
["cat"; "/new"]], "test content")],
"resize an LVM logical volume",
"\
@@ -3560,7 +3560,7 @@ and C<guestfs_setcon>");
[InitEmpty, Always, TestOutput (
[["part_disk"; "/dev/sda"; "mbr"];
["mkfs_b"; "ext2"; "4096"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"];
["mount_options"; ""; "/dev/sda1"; "/"];
["write_file"; "/new"; "new file contents"; "0"];
["cat"; "/new"]], "new file contents")],
"make a filesystem with block size",
@@ -3575,7 +3575,7 @@ are C<1024>, C<2048> or C<4096> only.");
[["sfdiskM"; "/dev/sda"; ",100 ,"];
["mke2journal"; "4096"; "/dev/sda1"];
["mke2fs_J"; "ext2"; "4096"; "/dev/sda2"; "/dev/sda1"];
["mount"; "/dev/sda2"; "/"];
["mount_options"; ""; "/dev/sda2"; "/"];
["write_file"; "/new"; "new file contents"; "0"];
["cat"; "/new"]], "new file contents")],
"make ext2/3/4 external journal",
@@ -3590,7 +3590,7 @@ to the command:
[["sfdiskM"; "/dev/sda"; ",100 ,"];
["mke2journal_L"; "4096"; "JOURNAL"; "/dev/sda1"];
["mke2fs_JL"; "ext2"; "4096"; "/dev/sda2"; "JOURNAL"];
["mount"; "/dev/sda2"; "/"];
["mount_options"; ""; "/dev/sda2"; "/"];
["write_file"; "/new"; "new file contents"; "0"];
["cat"; "/new"]], "new file contents")],
"make ext2/3/4 external journal with label",
@@ -3603,7 +3603,7 @@ This creates an ext2 external journal on C<device> with label C<label>.");
[["sfdiskM"; "/dev/sda"; ",100 ,"];
["mke2journal_U"; "4096"; uuid; "/dev/sda1"];
["mke2fs_JU"; "ext2"; "4096"; "/dev/sda2"; uuid];
["mount"; "/dev/sda2"; "/"];
["mount_options"; ""; "/dev/sda2"; "/"];
["write_file"; "/new"; "new file contents"; "0"];
["cat"; "/new"]], "new file contents")]),
"make ext2/3/4 external journal with UUID",
@@ -4218,7 +4218,7 @@ Rename a logical volume C<logvol> with the new name C<newlogvol>.");
["vg_activate"; "false"; "VG"];
["vgrename"; "VG"; "VG2"];
["vg_activate"; "true"; "VG2"];
["mount"; "/dev/VG2/LV"; "/"];
["mount_options"; ""; "/dev/VG2/LV"; "/"];
["vgs"]], ["VG2"])],
"rename an LVM volume group",
"\
@@ -6500,7 +6500,7 @@ and generate_one_test_body name i test_name init test =
["lvm_remove_all"];
["part_disk"; "/dev/sda"; "mbr"];
["mkfs"; "ext2"; "/dev/sda1"];
["mount"; "/dev/sda1"; "/"]]
["mount_options"; ""; "/dev/sda1"; "/"]]
| InitBasicFSonLVM ->
pr " /* InitBasicFSonLVM for %s: create ext2 on /dev/VG/LV */\n"
test_name;
@@ -6513,7 +6513,7 @@ and generate_one_test_body name i test_name init test =
["vgcreate"; "VG"; "/dev/sda1"];
["lvcreate"; "LV"; "VG"; "8"];
["mkfs"; "ext2"; "/dev/VG/LV"];
["mount"; "/dev/VG/LV"; "/"]]
["mount_options"; ""; "/dev/VG/LV"; "/"]]
| InitISOFS ->
pr " /* InitISOFS for %s */\n" test_name;
List.iter (generate_test_command_call test_name)

9
src/guestfs.pod
View File

@@ -558,6 +558,15 @@ Note that in L<guestfish(3)> I<autosync is the default>. So quick and
dirty guestfish scripts that forget to sync will work just fine, which
can make this extra-puzzling if you are trying to debug a problem.
=item Mount option C<-o sync> should not be the default.
If you use C<guestfs_mount>, then C<-o sync,noatime> are added
implicitly. However C<-o sync> does not add any reliability benefit,
but does have a very large performance impact.
The work around is to use C<guestfs_mount_options> and set the mount
options that you actually want to use.
=item Read-only should be the default.
In L<guestfish(3)>, I<--ro> should be the default, and you should

2
test-tool/test-tool.c
View File

@@ -229,7 +229,7 @@ main (int argc, char *argv[])
exit (EXIT_FAILURE);
}
if (guestfs_mount (g, "/dev/sda1", "/") == -1) {
if (guestfs_mount_options (g, "", "/dev/sda1", "/") == -1) {
fprintf (stderr,
_("libguestfs-test-tool: failed to mount /dev/sda1 on /\n"));
exit (EXIT_FAILURE);