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Date: Tue, 29 Jul 2014 10:21:50 +0200
From: Michael Kerrisk <mtk.manpages@...il.com>
To: Abhi Das <adas@...hat.com>
Cc: Linux Kernel <linux-kernel@...r.kernel.org>,
Linux-Fsdevel <linux-fsdevel@...r.kernel.org>,
cluster-devel <cluster-devel@...hat.com>,
Linux API <linux-api@...r.kernel.org>
Subject: Re: [RFC PATCH 1/2] fs: Add dirreadahead syscall and VFS hooks
[CC+=linux-api]
On Fri, Jul 25, 2014 at 7:37 PM, Abhi Das <adas@...hat.com> wrote:
> Also adds a void *opaque field to struct dir_context that can be
> used by filesystems to temporarily store any context as this
> struct gets passed around in the fs.
>
> Signed-off-by: Abhi Das <adas@...hat.com>
> ---
> arch/x86/syscalls/syscall_32.tbl | 1 +
> arch/x86/syscalls/syscall_64.tbl | 1 +
> fs/readdir.c | 49 ++++++++++++++++++++++++++++++++++++++++
> include/linux/fs.h | 3 +++
> 4 files changed, 54 insertions(+)
>
> diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
> index d6b8679..3e0ef85 100644
> --- a/arch/x86/syscalls/syscall_32.tbl
> +++ b/arch/x86/syscalls/syscall_32.tbl
> @@ -360,3 +360,4 @@
> 351 i386 sched_setattr sys_sched_setattr
> 352 i386 sched_getattr sys_sched_getattr
> 353 i386 renameat2 sys_renameat2
> +354 i386 dirreadahead sys_dirreadahead
> diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
> index ec255a1..2ec0991 100644
> --- a/arch/x86/syscalls/syscall_64.tbl
> +++ b/arch/x86/syscalls/syscall_64.tbl
> @@ -323,6 +323,7 @@
> 314 common sched_setattr sys_sched_setattr
> 315 common sched_getattr sys_sched_getattr
> 316 common renameat2 sys_renameat2
> +317 common dirreadahead sys_dirreadahead
>
> #
> # x32-specific system call numbers start at 512 to avoid cache impact
> diff --git a/fs/readdir.c b/fs/readdir.c
> index 33fd922..d216db7 100644
> --- a/fs/readdir.c
> +++ b/fs/readdir.c
> @@ -198,6 +198,7 @@ SYSCALL_DEFINE3(getdents, unsigned int, fd,
> struct linux_dirent __user * lastdirent;
> struct getdents_callback buf = {
> .ctx.actor = filldir,
> + .ctx.opaque = NULL,
> .count = count,
> .current_dir = dirent
> };
> @@ -278,6 +279,7 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd,
> struct linux_dirent64 __user * lastdirent;
> struct getdents_callback64 buf = {
> .ctx.actor = filldir64,
> + .ctx.opaque = NULL,
> .count = count,
> .current_dir = dirent
> };
> @@ -304,3 +306,50 @@ SYSCALL_DEFINE3(getdents64, unsigned int, fd,
> fdput(f);
> return error;
> }
> +
> +SYSCALL_DEFINE3(dirreadahead, unsigned int, fd,
> + loff_t __user *, offset, unsigned int, count)
> +{
> + struct fd f;
> + struct inode *inode;
> + int error = -ENOTDIR;
> + loff_t off = 0;
> + struct dir_context ctx = {.actor = NULL, .opaque = NULL};
> +
> + if (!count)
> + return -EINVAL;
> +
> + f = fdget(fd);
> + if (!f.file)
> + return -EBADF;
> +
> + inode = f.file->f_path.dentry->d_inode;
> +
> + error = -ENOTSUPP;
> + if (!f.file->f_op || !f.file->f_op->dir_readahead)
> + goto out;
> +
> + error = security_file_permission(f.file, MAY_READ);
> + if (error)
> + goto out;
> +
> + error = -EFAULT;
> + if (__get_user(ctx.pos, offset))
> + goto out;
> +
> + error = mutex_lock_killable(&inode->i_mutex);
> + if (error)
> + goto out;
> +
> + error = -ENOENT;
> + if (!IS_DEADDIR(inode)) {
> + error = f.file->f_op->dir_readahead(f.file, &ctx, count);
> + if (__put_user(ctx.pos, offset))
> + error = -EFAULT;
> + file_accessed(f.file);
> + }
> + mutex_unlock(&inode->i_mutex);
> +out:
> + fdput(f);
> + return error;
> +}
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 338e6f7..fae4a6e 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1438,9 +1438,11 @@ int fiemap_check_flags(struct fiemap_extent_info *fieinfo, u32 fs_flags);
> * to have different dirent layouts depending on the binary type.
> */
> typedef int (*filldir_t)(void *, const char *, int, loff_t, u64, unsigned);
> +
> struct dir_context {
> const filldir_t actor;
> loff_t pos;
> + void *opaque;
> };
>
> struct block_device_operations;
> @@ -1463,6 +1465,7 @@ struct file_operations {
> ssize_t (*read_iter) (struct kiocb *, struct iov_iter *);
> ssize_t (*write_iter) (struct kiocb *, struct iov_iter *);
> int (*iterate) (struct file *, struct dir_context *);
> + int (*dir_readahead) (struct file *, struct dir_context *, unsigned int);
> unsigned int (*poll) (struct file *, struct poll_table_struct *);
> long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long);
> long (*compat_ioctl) (struct file *, unsigned int, unsigned long);
> --
> 1.8.1.4
>
> --
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--
Michael Kerrisk Linux man-pages maintainer;
http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface", http://blog.man7.org/
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