Re: [PATCH][RFC] fs: Add new pre-allocation ioctls to vfs for compatibility with legacy xfs ioctls

Felix Blyakher
2008-12-18T06:53:08Z

On Dec 15, 2008, at 2:04 AM, 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.

I don't think we can use sys_fallocate for XFS_IOC_UNRESVSP*
commands, which suppose to release currently allocated file
blocks.
See more comments below.

Felix

> Note: These legacy ioctls are also implemented by OCFS2.
>
> There are some things that I'm not sure about:
> 1. Should the struct space_resv be exposed to user-space? If not,
> then what would be the right place to put it? And the ioctl
> definitions?
> 2. Should the corresponding ioctls be removed from ocfs2?
>
> Signed-off-by: Ankit Jain <me@ankitjain.org>
> ---
> fs/ioctl.c | 37 +++++++++++++++++++++++++++
> fs/open.c | 51 ++++++++++++++++++-------------------
> include/linux/falloc.h | 19 ++++++++++++++
> include/linux/fs.h | 2 +
> 4 files changed, 83 insertions(+), 26 deletions(-)
>
> diff --git a/fs/ioctl.c b/fs/ioctl.c
> index 43e8b2c..5e565c8 100644
> --- a/fs/ioctl.c
> +++ b/fs/ioctl.c
> @@ -15,6 +15,7 @@
> #include <linux/uaccess.h>
> #include <linux/writeback.h>
> #include <linux/buffer_head.h>
> +#include <linux/falloc.h>
>
> #include <asm/ioctls.h>
>
> @@ -346,6 +347,37 @@ EXPORT_SYMBOL(generic_block_fiemap);
>
> #endif /* CONFIG_BLOCK */
>
> +/*
> + * This provides compatibility with legacy XFS pre-allocation ioctls
> + * which predate the fallocate syscall.
> + *
> + * Only the l_start, l_len and l_whence fields of the 'struct
> space_resv'
> + * are used here, rest are ignored.
> + */
> +static int ioctl_preallocate(struct file *filp, unsigned long arg)
> +{
> + struct inode *inode = filp->f_path.dentry->d_inode;
> + struct space_resv sr;
> +
> + if (copy_from_user(&sr, (struct space_resv __user *) arg, sizeof
> (sr)))
> + return -EFAULT;
> +
> + switch (sr.l_whence) {
> + case SEEK_SET:
> + break;
> + case SEEK_CUR:
> + sr.l_start += filp->f_pos;
> + break;
> + case SEEK_END:
> + sr.l_start += i_size_read(inode);
> + break;
> + default:
> + return -EINVAL;
> + }
> +
> + return do_fallocate(filp, FALLOC_FL_KEEP_SIZE, sr.l_start,
> sr.l_len);
> +}
> +
> static int file_ioctl(struct file *filp, unsigned int cmd,
> unsigned long arg)
> {
> @@ -361,6 +393,11 @@ 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:
> + case F_IOC_UNRESVSP:
> + case F_IOC_UNRESVSP64:
> + return ioctl_preallocate(filp, arg);

At this point the original command 'cmd' is dropped,
and ioctl_preallocate() assumes F_IOC_RESVSP*.
Indeed, in the following path

ioctl_preallocate
do_fallocate
.fallocate/xfs_vn_fallocate
xfs_change_file_space(XFS_IOC_RESVSP)

UNRESVSP is never considered.

> }
>
> return vfs_ioctl(filp, cmd, arg);
> diff --git a/fs/open.c b/fs/open.c
> index 83cdb9d..0703bcb 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -360,62 +360,61 @@ asmlinkage long sys_ftruncate64(unsigned int
> fd, loff_t length)
> }
> #endif
>
> -asmlinkage long sys_fallocate(int fd, int mode, loff_t offset,
> loff_t len)
> +long do_fallocate(struct file *file, int mode, loff_t offset,
> loff_t len)
> {
> - struct file *file;
> struct inode *inode;
> - long ret = -EINVAL;
> + long ret;
>
> if (offset < 0 || len <= 0)
> - goto out;
> + return -EINVAL;
>
> /* Return error if mode is not supported */
> - ret = -EOPNOTSUPP;
> if (mode && !(mode & FALLOC_FL_KEEP_SIZE))
> - goto out;
> + return -EOPNOTSUPP;
>
> - ret = -EBADF;
> - file = fget(fd);
> - if (!file)
> - goto out;
> - if (!(file->f_mode & FMODE_WRITE))
> - goto out_fput;
> + if (!file || !(file->f_mode & FMODE_WRITE))
> + return -EBADF;
> /*
> * Revalidate the write permissions, in case security policy has
> * changed since the files were opened.
> */
> ret = security_file_permission(file, MAY_WRITE);
> if (ret)
> - goto out_fput;
> + return ret;
>
> inode = file->f_path.dentry->d_inode;
> -
> - ret = -ESPIPE;
> if (S_ISFIFO(inode->i_mode))
> - goto out_fput;
> + return -ESPIPE;
>
> - ret = -ENODEV;
> /*
> * Let individual file system decide if it supports preallocation
> * for directories or not.
> */
> if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
> - goto out_fput;
> + return -ENODEV;
>
> - ret = -EFBIG;
> /* Check for wrap through zero too */
> if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len)
> < 0))
> - goto out_fput;
> + return -EFBIG;
>
> if (inode->i_op && inode->i_op->fallocate)
> - ret = inode->i_op->fallocate(inode, mode, offset, len);
> + return inode->i_op->fallocate(inode, mode, offset, len);
> else
> - ret = -EOPNOTSUPP;
> + return -EOPNOTSUPP;
> +}
>
> -out_fput:
> - fput(file);
> -out:
> - return ret;
> +asmlinkage long sys_fallocate(int fd, int mode, loff_t offset,
> loff_t len)
> +{
> + struct file *file;
> + int error = -EBADF;
> +
> + file = fget(fd);
> + if (file) {
> + error = do_fallocate(file, mode, offset, len);
> + fput(file);
> + }
> +
> + return error;
> }
>
> /*
> diff --git a/include/linux/falloc.h b/include/linux/falloc.h
> index 8e912ab..4f2a727 100644
> --- a/include/linux/falloc.h
> +++ b/include/linux/falloc.h
> @@ -3,4 +3,23 @@
>
> #define FALLOC_FL_KEEP_SIZE 0x01 /* default is extend size */
>
> +/*
> + * Space reservation / allocation ioctls and argument structure
> + * are designed to be compatible with the legacy XFS ioctls.
> + */
> +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_UNRESVSP _IOW('X', 41, struct space_resv)
> +#define F_IOC_RESVSP64 _IOW('X', 42, struct space_resv)
> +#define F_IOC_UNRESVSP64 _IOW('X', 43, struct space_resv)
> +
> #endif /* _FALLOC_H_ */
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 4a853ef..b1d8f12 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1671,6 +1671,8 @@ static inline int break_lease(struct inode
> *inode, unsigned int mode)
>
> extern int do_truncate(struct dentry *, loff_t start, unsigned int
> time_attrs,
> struct file *filp);
> +extern long do_fallocate(struct file *file, int mode, loff_t offset,
> + loff_t len);
> extern long do_sys_open(int dfd, const char __user *filename, int
> flags,
> int mode);
> extern struct file *filp_open(const char *, int, int);
> --
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