linux-ext4 - RE: + ext2-get-rid-of-most-mentions-of-xip-in-ext2.patch added to -mm tree

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Message-ID: <100D68C7BA14664A8938383216E40DE04085342E@FMSMSX114.amr.corp.intel.com>
Date:	Fri, 16 Jan 2015 21:09:03 +0000
From:	"Wilcox, Matthew R" <matthew.r.wilcox@...el.com>
To:	Jan Kara <jack@...e.cz>
CC:	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"Dilger, Andreas" <andreas.dilger@...el.com>,
	"axboe@...nel.dk" <axboe@...nel.dk>,
	"boaz@...xistor.com" <boaz@...xistor.com>,
	"david@...morbit.com" <david@...morbit.com>,
	"hch@....de" <hch@....de>,
	"kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
	"mathieu.desnoyers@...icios.com" <mathieu.desnoyers@...icios.com>,
	"rdunlap@...radead.org" <rdunlap@...radead.org>,
	"ross.zwisler@...ux.intel.com" <ross.zwisler@...ux.intel.com>,
	"tytso@....edu" <tytso@....edu>,
	"mm-commits@...r.kernel.org" <mm-commits@...r.kernel.org>,
	"linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: RE: + ext2-get-rid-of-most-mentions-of-xip-in-ext2.patch added to
 -mm tree

Ugh ... this works better from my linux.intel.com address ...

-----Original Message-----
From: Jan Kara [mailto:jack@...e.cz] 
Sent: Thursday, January 15, 2015 2:31 AM
To: Wilcox, Matthew R
Cc: akpm@...ux-foundation.org; Dilger, Andreas; axboe@...nel.dk; boaz@...xistor.com; david@...morbit.com; hch@....de; jack@...e.cz; kirill.shutemov@...ux.intel.com; mathieu.desnoyers@...icios.com; rdunlap@...radead.org; ross.zwisler@...ux.intel.com; tytso@....edu; mm-commits@...r.kernel.org; linux-ext4@...r.kernel.org
Subject: Re: + ext2-get-rid-of-most-mentions-of-xip-in-ext2.patch added to -mm tree

On Mon 12-01-15 15:11:11, Andrew Morton wrote:
...
> diff -puN fs/ext2/ext2.h~ext2-get-rid-of-most-mentions-of-xip-in-ext2 fs/ext2/ext2.h
> --- a/fs/ext2/ext2.h~ext2-get-rid-of-most-mentions-of-xip-in-ext2
> +++ a/fs/ext2/ext2.h
> @@ -380,14 +380,15 @@ struct ext2_inode {
>  #define EXT2_MOUNT_NO_UID32		0x000200  /* Disable 32-bit UIDs */
>  #define EXT2_MOUNT_XATTR_USER		0x004000  /* Extended user attributes */
>  #define EXT2_MOUNT_POSIX_ACL		0x008000  /* POSIX Access Control Lists */
> -#ifdef CONFIG_FS_DAX
> -#define EXT2_MOUNT_XIP			0x010000  /* Execute in place */
> -#else
> -#define EXT2_MOUNT_XIP			0
> -#endif
> +#define EXT2_MOUNT_XIP			0x010000  /* Obsolete, use DAX */
>  #define EXT2_MOUNT_USRQUOTA		0x020000  /* user quota */
>  #define EXT2_MOUNT_GRPQUOTA		0x040000  /* group quota */
>  #define EXT2_MOUNT_RESERVATION		0x080000  /* Preallocation */
> +#ifdef CONFIG_FS_DAX
> +#define EXT2_MOUNT_DAX			0x100000  /* Direct Access */
> +#else
> +#define EXT2_MOUNT_DAX			0
> +#endif
  Why do you define EXT2_MOUNT_DAX differently depending on CONFIG_FS_DAX?
  That seems unnecessary...

That's copied from the original XIP code.  I think the intent is to make the XIP/DAX code disappear from the module, rather than being dead code cluttering up the object file.

...
> diff -puN fs/ext2/super.c~ext2-get-rid-of-most-mentions-of-xip-in-ext2 fs/ext2/super.c
> --- a/fs/ext2/super.c~ext2-get-rid-of-most-mentions-of-xip-in-ext2
> +++ a/fs/ext2/super.c
> @@ -294,6 +294,8 @@ static int ext2_show_options(struct seq_
>  #ifdef CONFIG_FS_DAX
>  	if (sbi->s_mount_opt & EXT2_MOUNT_XIP)
>  		seq_puts(seq, ",xip");
> +	if (sbi->s_mount_opt & EXT2_MOUNT_DAX)
> +		seq_puts(seq, ",dax");
>  #endif
>  
>  	if (!test_opt(sb, RESERVATION))
  So if someone mounts filesystem with -o xip, /proc/mounts will show both
'xip' and 'dax'. OK, probably makes sense.

Yeah, I thought that was the best migration path; somebody might have a script that's checking for 'xip' in /proc/mounts.
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