[PATCH V2] mke2fs: add discard to default mke2fs.conf and disable by default

[Eric Sandeen <sandeen@redhat.com>]

Discard is a very big hammer.  If it succeeds, there's no undo
or going back; on the other hand, on some devices the giant discard
issued at mkfs time makes them go offline.  

Although I'm reluctant to waffle back and forth on default behavior,
I think this disabling it by default the prudent thing to do.

This patch also adds the discard option into the default mke2fs.conf
file; although it could be set, it was not in the template.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

V2: handle discard disable via "-K" since it's parsed *before* we get
the default.  The extended options are parsed later, and will override
the mke2fs.conf default without problems.

diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index 023ba49..a005eca 100644
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -277,11 +277,11 @@ Attempt to discard blocks at mkfs time (discarding blocks initially is useful
 on solid state devices and sparse / thin-provisioned storage). When the device
 advertises that discard also zeroes data (any subsequent read after the discard
 and before write returns zero), then mark all not-yet-zeroed inode tables as
-zeroed. This significantly speeds up filesystem initialization. This is set
-as default.
+zeroed. This significantly speeds up filesystem initialization. This is disabled
+by default.
 .TP
 .BI nodiscard
-Do not attempt to discard blocks at mkfs time.
+Do not attempt to discard blocks at mkfs time.  This is the default.
 .TP
 .BI quotatype
 Specify which quota type ('usr' or 'grp') is to be initialized. This
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index bbf477a..fa11da6 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -84,7 +84,7 @@ int	cflag;
 int	verbose;
 int	quiet;
 int	super_only;
-int	discard = 1;	/* attempt to discard device before fs creation */
+int	discard;	/* attempt to discard device before fs creation? */
 int	direct_io;
 int	force;
 int	noaction;
@@ -1266,6 +1266,7 @@ static void PRS(int argc, char *argv[])
 	double		reserved_ratio = -1.0;
 	int		lsector_size = 0, psector_size = 0;
 	int		show_version_only = 0;
+	int		nodiscard = 0;
 	unsigned long long num_inodes = 0; /* unsigned long long to catch too-large input */
 	errcode_t	retval;
 	char *		oldpath = getenv("PATH");
@@ -1444,7 +1445,7 @@ profile_error:
 					  "should not be used anymore. Use "
 					  "\'-E nodiscard\' extended option "
 					  "instead!\n"));
-			discard = 0;
+			nodiscard = 1;
 			break;
 		case 'j':
 			if (!journal_size)
@@ -1985,7 +1986,8 @@ profile_error:
 	lazy_itable_init = get_bool_from_profile(fs_types,
 						 "lazy_itable_init",
 						 lazy_itable_init);
-	discard = get_bool_from_profile(fs_types, "discard" , discard);
+	/* nodiscard is set if -K was used, extended discard opts parsed later */
+	discard = nodiscard ? 0 : get_bool_from_profile(fs_types, "discard" , 0);
 	journal_flags |= get_bool_from_profile(fs_types,
 					       "lazy_journal_init", 0) ?
 					       EXT2_MKJOURNAL_LAZYINIT : 0;
diff --git a/misc/mke2fs.conf.in b/misc/mke2fs.conf.in
index 178733f..db6decb 100644
--- a/misc/mke2fs.conf.in
+++ b/misc/mke2fs.conf.in
@@ -2,6 +2,7 @@
 	base_features = sparse_super,filetype,resize_inode,dir_index,ext_attr
 	default_mntopts = acl,user_xattr
 	enable_periodic_fsck = 0
+	discard = 0
 	blocksize = 4096
 	inode_size = 256
 	inode_ratio = 16384