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

Amit K. Arora
2007-06-25T15:33:18Z

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@in.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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