On 4/17/13 3:04 PM, Eric Sandeen wrote:
> 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@xxxxxxxxxx>
Sorry, scratch this; it won't work if, say, discard=1 in the conf
file and the user specifies -E nodiscard or -K; it'll turn it back
on after those options are processed, I think. I'll send another
patch later when I'm not firing it off too quickly from a conference. ;)
-Eric
> ---
>
> If disabling by default isn't desired, we should at least include
> the mke2fs.conf.in change (set to 1).
>
> Thanks,
> -Eric
>
> 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..d723ee7 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;
> 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
>
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