On 2011-11-16 12:22:41, Thieu Le wrote:
> Export fallocate facility so layered file systems such as ecryptfs can
> take advantage of this feature. One example of the need for fallocate
> is by ecryptfs. ecryptfs has recently switched to a writeback cache
> model so its dirty pages are not written to the lower file system
> immediately. In order to ensure that space is available when the page
> is later written, ecryptfs can efficiently preallocate that space using
> vfs_fallocate().
>
> vfs_fallocate() does not perform all of the checkings of do_fallocate()
> because those checks are done higher in the stack. Checking of offset and
> len are done by rw_verify_area() and generic_write_checks(). These
> functions are called by VFS before ecryptfs invokes vfs_fallocate() in its
> ecryptfs_write_end() function. And since ecryptfs directly opens the lower
> file, it ensures that the file is opened with the proper flags and mode.
This looks good to me. Feel free to add my Reviewed-by. Of course, it
will need final sign-off by Al and/or Christoph.
Tyler
>
> Signed-off-by: Thieu Le <thieule@xxxxxxxxxxxx>
> ---
> fs/open.c | 32 ++++++++++++++++++++------------
> include/linux/fs.h | 2 ++
> 2 files changed, 22 insertions(+), 12 deletions(-)
>
> diff --git a/fs/open.c b/fs/open.c
> index 22c41b5..65c0049 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -214,13 +214,9 @@ SYSCALL_ALIAS(sys_ftruncate64, SyS_ftruncate64);
> #endif /* BITS_PER_LONG == 32 */
>
>
> -int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> +int vfs_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> {
> struct inode *inode = file->f_path.dentry->d_inode;
> - long ret;
> -
> - if (offset < 0 || len <= 0)
> - return -EINVAL;
>
> /* Return error if mode is not supported */
> if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
> @@ -231,13 +227,28 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> !(mode & FALLOC_FL_KEEP_SIZE))
> return -EOPNOTSUPP;
>
> - if (!(file->f_mode & FMODE_WRITE))
> - return -EBADF;
> -
> /* It's not possible punch hole on append only file */
> if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
> return -EPERM;
>
> + if (!file->f_op->fallocate)
> + return -EOPNOTSUPP;
> +
> + return file->f_op->fallocate(file, mode, offset, len);
> +}
> +EXPORT_SYMBOL(vfs_fallocate);
> +
> +int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> +{
> + struct inode *inode = file->f_path.dentry->d_inode;
> + long ret;
> +
> + if (offset < 0 || len <= 0)
> + return -EINVAL;
> +
> + if (!(file->f_mode & FMODE_WRITE))
> + return -EBADF;
> +
> if (IS_IMMUTABLE(inode))
> return -EPERM;
>
> @@ -263,10 +274,7 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
> if (((offset + len) > inode->i_sb->s_maxbytes) || ((offset + len) < 0))
> return -EFBIG;
>
> - if (!file->f_op->fallocate)
> - return -EOPNOTSUPP;
> -
> - return file->f_op->fallocate(file, mode, offset, len);
> + return vfs_fallocate(file, mode, offset, len);
> }
>
> SYSCALL_DEFINE(fallocate)(int fd, int mode, loff_t offset, loff_t len)
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 0c4df26..e7d26ee 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1524,6 +1524,8 @@ extern int vfs_link(struct dentry *, struct inode *, struct dentry *);
> extern int vfs_rmdir(struct inode *, struct dentry *);
> extern int vfs_unlink(struct inode *, struct dentry *);
> extern int vfs_rename(struct inode *, struct dentry *, struct inode *, struct dentry *);
> +extern int vfs_fallocate(struct file *file, int mode, loff_t offset,
> + loff_t len);
>
> /*
> * VFS dentry helper functions.
> --
> 1.7.3.1
>
> --
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