mke2fs: add discard to default mke2fs.conf and disable by default

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 <[email protected]>

---

If disabling by default isn't desired, we should at least include the mke2fs.conf.in change (set to 1).

Thanks,

(quoted diff) +0 -1

-Eric

misc/mke2fs.8.in +3 -3

index 023ba49..a005eca 100644
@@ -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

misc/mke2fs.c +1 -1

index bbf477a..d723ee7 100644
@@ -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;

misc/mke2fs.conf.in +1 -1

index 178733f..db6decb 100644
@@ -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
 
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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 <[email protected]>

---

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.

misc/mke2fs.8.in +0 -0

index 023ba49..a005eca 100644
@@ -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

misc/mke2fs.8.in +2 -2

-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

misc/mke2fs.8.in +1 -1

-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

misc/mke2fs.c +5 -3

index bbf477a..fa11da6 100644
@@ -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;

misc/mke2fs.conf.in +1 -1

index 178733f..db6decb 100644
@@ -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
 
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