linux-kernel - Re: [PATCH 4/7][TAKE5] support new modes in fallocate

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Message-ID: <20070625150320.GA8686@amitarora.in.ibm.com>
Date:	Mon, 25 Jun 2007 20:33:20 +0530
From:	"Amit K. Arora" <aarora@...ux.vnet.ibm.com>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-ext4@...r.kernel.org
Cc:	David Chinner <dgc@....com>,
	Andreas Dilger <adilger@...sterfs.com>, suparna@...ibm.com,
	cmm@...ibm.com, xfs@....sgi.com
Subject: Re: [PATCH 4/7][TAKE5] support new modes in fallocate

I have not implemented FA_FL_FREE_ENOSPC and FA_ZERO_SPACE flags yet, as
*suggested* by Andreas in http://lkml.org/lkml/2007/6/14/323  post.
If it is decided that these flags are also needed, I will update this
patch. Thanks!

On Mon, Jun 25, 2007 at 07:15:00PM +0530, Amit K. Arora wrote:
> Implement new flags and values for mode argument.
> 
> This patch implements the new flags and values for the "mode" argument
> of the fallocate system call. It is based on the discussion between
> Andreas Dilger and David Chinner on the man page proposed (by the later)
> on fallocate.
> 
> Signed-off-by: Amit Arora <aarora@...ibm.com>
> 
> Index: linux-2.6.22-rc4/include/linux/fs.h
> ===================================================================
> --- linux-2.6.22-rc4.orig/include/linux/fs.h
> +++ linux-2.6.22-rc4/include/linux/fs.h
> @@ -267,15 +267,16 @@ extern int dir_notify_enable;
>  #define SYNC_FILE_RANGE_WAIT_AFTER	4
> 
>  /*
> - * sys_fallocate modes
> - * Currently sys_fallocate supports two modes:
> - * FA_ALLOCATE  : This is the preallocate mode, using which an application/user
> - *		  may request (pre)allocation of blocks.
> - * FA_DEALLOCATE: This is the deallocate mode, which can be used to free
> - *		  the preallocated blocks.
> + * sys_fallocate mode flags and values
>   */
> -#define FA_ALLOCATE	0x1
> -#define FA_DEALLOCATE	0x2
> +#define FA_FL_DEALLOC	0x01 /* default is allocate */
> +#define FA_FL_KEEP_SIZE	0x02 /* default is extend/shrink size */
> +#define FA_FL_DEL_DATA	0x04 /* default is keep written data on DEALLOC */
> +
> +#define FA_ALLOCATE	0
> +#define FA_DEALLOCATE	FA_FL_DEALLOC
> +#define FA_RESV_SPACE	FA_FL_KEEP_SIZE
> +#define FA_UNRESV_SPACE	(FA_FL_DEALLOC | FA_FL_KEEP_SIZE | FA_FL_DEL_DATA)
> 
>  #ifdef __KERNEL__
> 
> Index: linux-2.6.22-rc4/fs/open.c
> ===================================================================
> --- linux-2.6.22-rc4.orig/fs/open.c
> +++ linux-2.6.22-rc4/fs/open.c
> @@ -356,23 +356,26 @@ asmlinkage long sys_ftruncate64(unsigned
>   * sys_fallocate - preallocate blocks or free preallocated blocks
>   * @fd: the file descriptor
>   * @mode: mode specifies if fallocate should preallocate blocks OR free
> - *	  (unallocate) preallocated blocks. Currently only FA_ALLOCATE and
> - *	  FA_DEALLOCATE modes are supported.
> + *	  (unallocate) preallocated blocks.
>   * @offset: The offset within file, from where (un)allocation is being
>   *	    requested. It should not have a negative value.
>   * @len: The amount (in bytes) of space to be (un)allocated, from the offset.
>   *
>   * This system call, depending on the mode, preallocates or unallocates blocks
>   * for a file. The range of blocks depends on the value of offset and len
> - * arguments provided by the user/application. For FA_ALLOCATE mode, if this
> + * arguments provided by the user/application. For FA_ALLOCATE and
> + * FA_RESV_SPACE modes, if the sys_fallocate()
>   * system call succeeds, subsequent writes to the file in the given range
>   * (specified by offset & len) should not fail - even if the file system
>   * later becomes full. Hence the preallocation done is persistent (valid
> - * even after reopen of the file and remount/reboot).
> + * even after reopen of the file and remount/reboot). If FA_RESV_SPACE mode
> + * is passed, the file size will not be changed even if the preallocation
> + * is beyond EOF.
>   *
>   * It is expected that the ->fallocate() inode operation implemented by the
>   * individual file systems will update the file size and/or ctime/mtime
> - * depending on the mode and also on the success of the operation.
> + * depending on the mode (change is visible to user or not - say file size)
> + * and obviously, on the success of the operation.
>   *
>   * Note: Incase the file system does not support preallocation,
>   * posix_fallocate() should fall back to the library implementation (i.e.
> @@ -398,7 +401,8 @@ asmlinkage long sys_fallocate(int fd, in
> 
>  	/* Return error if mode is not supported */
>  	ret = -EOPNOTSUPP;
> -	if (mode != FA_ALLOCATE && mode != FA_DEALLOCATE)
> +	if (!(mode == FA_ALLOCATE || mode == FA_DEALLOCATE ||
> +		mode == FA_RESV_SPACE || mode == FA_UNRESV_SPACE))
>  		goto out;
> 
>  	ret = -EBADF;
> -
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