I plan to release this in an upcoming 1.40.6 release, along with code
that allows "tune2fs -E test_fs" to work on ext4 filesystems. The idea
is that if I can get this into community distro's, it will make it
easier for them to experiment with ext4/ext4dev, with the appropriate
forward compatibility when sometime (hopefully 2.6.26 or 2.6.27?) we
rename ext4dev to ext4.
Any comments before I push this change out to the maint branch?
- Ted
commit feac6e49211a44ef6f560b3b362fb132a474a471
Author: Theodore Ts'o <[email protected]>
Date: Fri Feb 8 16:04:12 2008 -0500
blkid: Automatically chose between ext4 and ext4dev as appropriate
Add logic that on Linux systems will check for the presence of the
ext4dev filesystem; if it isn't present, fall back to ext4 for
filesystems that are marked as being "OK for use on test filesystem
code". If they are OK for use for in-development filesystem code, it
should also be fine to use stable filesystem code if there is no test
filesystem code (ext4dev) available.
The reverse is not true, of course. We don't ever want to mount a
production filesystem using test filesystem code unless the user gives
us explicit permission via "tune2fs -E test_fs".
Signed-off-by: "Theodore Ts'o" <[email protected]>
diff --git a/lib/blkid/probe.c b/lib/blkid/probe.c
index 492a36a..456e9bb 100644
--- a/lib/blkid/probe.c
+++ b/lib/blkid/probe.c
@@ -25,6 +25,7 @@
#ifdef HAVE_SYS_MKDEV_H
#include <sys/mkdev.h>
#endif
+#include <sys/utsname.h>
#ifdef HAVE_ERRNO_H
#include <errno.h>
#endif
@@ -158,6 +159,109 @@ static void get_ext2_info(blkid_dev dev, struct blkid_magic *id,
blkid_set_tag(dev, "SEC_TYPE", "ext2", sizeof("ext2"));
}
+/*
+ * Check to see if a filesystem is in /proc/filesystems.
+ * Returns 1 if found, 0 if not
+ */
+int fs_proc_check(const char *fs_name)
+{
+ FILE *f;
+ char buf[80], *cp, *t;
+
+ f = fopen("/proc/filesystems", "r");
+ if (!f)
+ return (0);
+ while (!feof(f)) {
+ if (!fgets(buf, sizeof(buf), f))
+ break;
+ cp = buf;
+ if (!isspace(*cp)) {
+ while (*cp && !isspace(*cp))
+ cp++;
+ }
+ while (*cp && isspace(*cp))
+ cp++;
+ if ((t = strchr(cp, '\n')) != NULL)
+ *t = 0;
+ if ((t = strchr(cp, '\t')) != NULL)
+ *t = 0;
+ if ((t = strchr(cp, ' ')) != NULL)
+ *t = 0;
+ if (!strcmp(fs_name, cp)) {
+ fclose(f);
+ return (1);
+ }
+ }
+ fclose(f);
+ return (0);
+}
+
+/*
+ * Check to see if a filesystem is available as a module
+ * Returns 1 if found, 0 if not
+ */
+int check_for_modules(const char *fs_name)
+{
+ struct utsname uts;
+ FILE *f;
+ char buf[1024], *cp, *t;
+ int i;
+
+ if (uname(&uts))
+ return (0);
+ snprintf(buf, sizeof(buf), "/lib/modules/%s/modules.dep", uts.release);
+
+ f = fopen(buf, "r");
+ if (!f)
+ return (0);
+ while (!feof(f)) {
+ if (!fgets(buf, sizeof(buf), f))
+ break;
+ if ((cp = strchr(buf, ':')) != NULL)
+ *cp = 0;
+ else
+ continue;
+ if ((cp = strrchr(buf, '/')) != NULL)
+ cp++;
+ i = strlen(cp);
+ if (i > 3) {
+ t = cp + i - 3;
+ if (!strcmp(t, ".ko"))
+ *t = 0;
+ }
+ if (!strcmp(cp, fs_name))
+ return (1);
+ }
+ fclose(f);
+ return (0);
+}
+
+static int system_supports_ext4()
+{
+ static time_t last_check = 0;
+ static int ret = -1;
+ time_t now = time(0);
+
+ if (ret != -1 || (last_check - now) > 5)
+ return ret;
+ last_check = now;
+ ret = (fs_proc_check("ext4") || check_for_modules("ext4"));
+ return ret;
+}
+
+static int system_supports_ext4dev()
+{
+ static time_t last_check = 0;
+ static int ret = -1;
+ time_t now = time(0);
+
+ if (ret != -1 || (last_check - now) > 5)
+ return ret;
+ last_check = now;
+ ret = (fs_proc_check("ext4dev") || check_for_modules("ext4dev"));
+ return ret;
+}
+
static int probe_ext4dev(struct blkid_probe *probe,
struct blkid_magic *id,
unsigned char *buf)
@@ -165,10 +269,6 @@ static int probe_ext4dev(struct blkid_probe *probe,
struct ext2_super_block *es;
es = (struct ext2_super_block *)buf;
- /* Distinguish between ext4dev and other filesystems */
- if ((blkid_le32(es->s_flags) & EXT2_FLAGS_TEST_FILESYS) == 0)
- return -BLKID_ERR_PARAM;
-
/* Distinguish from jbd */
if (blkid_le32(es->s_feature_incompat) &
EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)
@@ -179,6 +279,22 @@ static int probe_ext4dev(struct blkid_probe *probe,
EXT3_FEATURE_COMPAT_HAS_JOURNAL))
return -BLKID_ERR_PARAM;
+ /*
+ * If the filesystem is marked as OK for use by in-development
+ * filesystem code, but ext4dev is not supported, and ext4 is,
+ * then don't call ourselves ext4dev, since we should be
+ * detected as ext4 in that case.
+ *
+ * If the filesystem is marked as in use by production
+ * filesystem, then it can only be used by ext4 and NOT by
+ * ext4dev, so always disclaim we are ext4dev in that case.
+ */
+ if (blkid_le32(es->s_flags) & EXT2_FLAGS_TEST_FILESYS) {
+ if (!system_supports_ext4dev() && system_supports_ext4())
+ return -BLKID_ERR_PARAM;
+ } else
+ return -BLKID_ERR_PARAM;
+
get_ext2_info(probe->dev, id, buf);
return 0;
}
@@ -189,10 +305,6 @@ static int probe_ext4(struct blkid_probe *probe, struct blkid_magic *id,
struct ext2_super_block *es;
es = (struct ext2_super_block *)buf;
- /* Distinguish from ext4dev */
- if (blkid_le32(es->s_flags) & EXT2_FLAGS_TEST_FILESYS)
- return -BLKID_ERR_PARAM;
-
/* Distinguish from jbd */
if (blkid_le32(es->s_feature_incompat) &
EXT3_FEATURE_INCOMPAT_JOURNAL_DEV)
@@ -210,6 +322,20 @@ static int probe_ext4(struct blkid_probe *probe, struct blkid_magic *id,
EXT3_FEATURE_INCOMPAT_UNSUPPORTED))
return -BLKID_ERR_PARAM;
+ /*
+ * If the filesystem is a OK for use by in-development
+ * filesystem code, and ext4dev is supported or ext4 is not
+ * supported, then don't call ourselves ext4, so we can redo
+ * the detection and mark the filesystem as ext4dev.
+ *
+ * If the filesystem is marked as in use by production
+ * filesystem, then it can only be used by ext4 and NOT by
+ * ext4dev.
+ */
+ if (blkid_le32(es->s_flags) & EXT2_FLAGS_TEST_FILESYS) {
+ if (system_supports_ext4dev() || !system_supports_ext4())
+ return -BLKID_ERR_PARAM;
+ }
get_ext2_info(probe->dev, id, buf);
return 0;
}
Theodore Ts'o wrote:
> I plan to release this in an upcoming 1.40.6 release, along with code
> that allows "tune2fs -E test_fs" to work on ext4 filesystems. The idea
> is that if I can get this into community distro's, it will make it
> easier for them to experiment with ext4/ext4dev, with the appropriate
> forward compatibility when sometime (hopefully 2.6.26 or 2.6.27?) we
> rename ext4dev to ext4.
>
> Any comments before I push this change out to the maint branch?
Seems logically correct to me... although it also seems like this has
gotten fairly complex by now, what with blkid rummaging around in
modules.dep, /proc files, etc...
-Eric
On Fri, Feb 08, 2008 at 04:50:37PM -0600, Eric Sandeen wrote:
> Theodore Ts'o wrote:
> > I plan to release this in an upcoming 1.40.6 release, along with code
> > that allows "tune2fs -E test_fs" to work on ext4 filesystems. The idea
> > is that if I can get this into community distro's, it will make it
> > easier for them to experiment with ext4/ext4dev, with the appropriate
> > forward compatibility when sometime (hopefully 2.6.26 or 2.6.27?) we
> > rename ext4dev to ext4.
> >
> > Any comments before I push this change out to the maint branch?
>
> Seems logically correct to me... although it also seems like this has
> gotten fairly complex by now, what with blkid rummaging around in
> modules.dep, /proc files, etc...
True, but the good thing is that we only need to do this in one
location, and it does the right thing. It also means that in the
future, even after ext4 is in production, if we want to do some
testing for some new optimizations or other ehancements in ext4, it's
a lot easier for us have both ext4 and ext4dev modules built at the
same time, where ext4dev would have our test code, and then once it's
stable and we're sure it's OK, we can commit it to mainline. This
makes life much more convenient for an ext4 developer who wants to
both use it in production as well as having an alternate "crash and
burn" ext4dev code that he or she is trying out.
So one of the things that this does mean, is after we do the
ext4dev->ext4 transition, we have some way for users to give us
permission to disable the test_fs bit --- so that in the future, when
we have need of that bit, we can use it again and not have to worry
about old filesystems that are now in production but still have the
test_fs bit set.
- Ted
On Feb 08, 2008 17:35 -0500, Theodore Ts'o wrote:
> I plan to release this in an upcoming 1.40.6 release, along with code
> that allows "tune2fs -E test_fs" to work on ext4 filesystems. The idea
> is that if I can get this into community distro's, it will make it
> easier for them to experiment with ext4/ext4dev, with the appropriate
> forward compatibility when sometime (hopefully 2.6.26 or 2.6.27?) we
> rename ext4dev to ext4.
>
> Any comments before I push this change out to the maint branch?
>
> - Ted
>
>
> @@ -158,6 +159,109 @@ static void get_ext2_info(blkid_dev dev, struct blkid_magic *id,
> blkid_set_tag(dev, "SEC_TYPE", "ext2", sizeof("ext2"));
> }
>
> +/*
> + * Check to see if a filesystem is in /proc/filesystems.
> + * Returns 1 if found, 0 if not
> + */
> +int fs_proc_check(const char *fs_name)
> +{
> +}
Sure.
> +int check_for_modules(const char *fs_name)
> +{
> +}
This part is quite fragile IMHO. Why not blindly do an attempt to load
this module via the equivalent of system("modprobe %s", fs_name) and then
call fs_proc_check() to see if it is available? That removes all of the
kernel/module knowlege/complexity from blkid.
Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.