On Fri, Dec 19, 2008 at 02:51:00AM +0530, Ankit Jain wrote:
> This patch adds ioctls to vfs for compatibility with legacy XFS
> pre-allocation ioctls (XFS_IOC_*RESVP*). The implementation
> effectively invokes sys_fallocate for the new ioctls.
> Note: These legacy ioctls are also implemented by OCFS2.
>
> Changes in v2:
> - Dropped the incorrect handling of *UNRESVSP* ioctl.
> - Made the ioctl and argument structure kernel only (__KERNEL__)
>
> Signed-off-by: Ankit Jain <me@xxxxxxxxxxxxx>
.....
> @@ -361,6 +393,9 @@ static int file_ioctl(struct file *filp, unsigned int cmd,
> return put_user(inode->i_sb->s_blocksize, p);
> case FIONREAD:
> return put_user(i_size_read(inode) - filp->f_pos, p);
> + case F_IOC_RESVSP:
> + case F_IOC_RESVSP64:
> + return ioctl_preallocate(filp, arg);
> }
>
> return vfs_ioctl(filp, cmd, arg);
Adding this here breaks XFS_IOC_RESVSP in subtle and interesting
ways.
XFS_IOC_RESVSP supports invisible I/O, and that means
XFS_IOC_RESVSP needs to be passed through to vfs_ioctl()
to vector to XFS to handle.
This happenѕ because:
> +struct space_resv {
> + __s16 l_type;
> + __s16 l_whence;
> + __s64 l_start;
> + __s64 l_len; /* len == 0 means until end of file */
> + __s32 l_sysid;
> + __u32 l_pid;
> + __s32 l_pad[4]; /* reserve area */
> +};
> +
> +#define F_IOC_RESVSP _IOW('X', 40, struct space_resv)
> +#define F_IOC_RESVSP64 _IOW('X', 42, struct space_resv)
Is the same as:
#define XFS_IOC_RESVSP _IOW ('X', 40, struct xfs_flock64)
#define XFS_IOC_RESVSP64 _IOW ('X', 42, struct xfs_flock64)
because:
typedef struct xfs_flock64 {
__s16 l_type;
__s16 l_whence;
__s64 l_start;
__s64 l_len; /* len == 0 means until end of file */
__s32 l_sysid;
__u32 l_pid;
__s32 l_pad[4]; /* reserve area */
} xfs_flock64_t;
is the same size as struct space_resv. Hence existing calls to
XFS_IOC_RESVSP will now vector incorrectly down the fallocate path
resulting in invisible operations will now be visible....
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
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