2008-02-12 21:03:46

by J. Bruce Fields

[permalink] [raw]
Subject: Re: [PATCH 01/11] NFS: Always enable NFS direct I/O

On Mon, Feb 11, 2008 at 05:11:32PM -0500, Chuck Lever wrote:
> Since O_DIRECT is a standard feature that is enabled in most distros,

Not all distros? Also, people that really need extremely small kernels
aren't using distro kernels, are they? Or does this not add any
significant size?

--b.

> eliminate the CONFIG_NFS_DIRECTIO build option, and change the
> fs/nfs/Makefile to always build in the NFS direct I/O engine.


>
> Signed-off-by: Chuck Lever <[email protected]>
> ---
>
> fs/Kconfig | 24 ------------------------
> fs/nfs/Makefile | 3 +--
> fs/nfs/file.c | 6 ------
> fs/nfs/internal.h | 5 -----
> 4 files changed, 1 insertions(+), 37 deletions(-)
>
> diff --git a/fs/Kconfig b/fs/Kconfig
> index 987b5d7..4965fd8 100644
> --- a/fs/Kconfig
> +++ b/fs/Kconfig
> @@ -1638,30 +1638,6 @@ config NFS_V4
>
> If unsure, say N.
>
> -config NFS_DIRECTIO
> - bool "Allow direct I/O on NFS files"
> - depends on NFS_FS
> - help
> - This option enables applications to perform uncached I/O on files
> - in NFS file systems using the O_DIRECT open() flag. When O_DIRECT
> - is set for a file, its data is not cached in the system's page
> - cache. Data is moved to and from user-level application buffers
> - directly. Unlike local disk-based file systems, NFS O_DIRECT has
> - no alignment restrictions.
> -
> - Unless your program is designed to use O_DIRECT properly, you are
> - much better off allowing the NFS client to manage data caching for
> - you. Misusing O_DIRECT can cause poor server performance or network
> - storms. This kernel build option defaults OFF to avoid exposing
> - system administrators unwittingly to a potentially hazardous
> - feature.
> -
> - For more details on NFS O_DIRECT, see fs/nfs/direct.c.
> -
> - If unsure, say N. This reduces the size of the NFS client, and
> - causes open() to return EINVAL if a file residing in NFS is
> - opened with the O_DIRECT flag.
> -
> config NFSD
> tristate "NFS server support"
> depends on INET
> diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
> index f54c4d7..344bccb 100644
> --- a/fs/nfs/Makefile
> +++ b/fs/nfs/Makefile
> @@ -8,7 +8,7 @@ EXTRA_CFLAGS = -W -Wall -Wextra -Wsign-compare \
> obj-$(CONFIG_NFS_FS) += nfs.o
>
> nfs-y := client.o dir.o file.o getroot.o inode.o super.o nfs2xdr.o \
> - pagelist.o proc.o read.o symlink.o unlink.o \
> + direct.o pagelist.o proc.o read.o symlink.o unlink.o \
> write.o namespace.o mount_clnt.o
> nfs-$(CONFIG_ROOT_NFS) += nfsroot.o
> nfs-$(CONFIG_NFS_V3) += nfs3proc.o nfs3xdr.o
> @@ -17,5 +17,4 @@ nfs-$(CONFIG_NFS_V4) += nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o \
> delegation.o idmap.o \
> callback.o callback_xdr.o callback_proc.o \
> nfs4namespace.o
> -nfs-$(CONFIG_NFS_DIRECTIO) += direct.o
> nfs-$(CONFIG_SYSCTL) += sysctl.o
> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
> index ef57a5a..10e8b80 100644
> --- a/fs/nfs/file.c
> +++ b/fs/nfs/file.c
> @@ -234,10 +234,8 @@ nfs_file_read(struct kiocb *iocb, const struct iovec *iov,
> ssize_t result;
> size_t count = iov_length(iov, nr_segs);
>
> -#ifdef CONFIG_NFS_DIRECTIO
> if (iocb->ki_filp->f_flags & O_DIRECT)
> return nfs_file_direct_read(iocb, iov, nr_segs, pos);
> -#endif
>
> dfprintk(VFS, "nfs: read(%s/%s, %[email protected]%lu)\n",
> dentry->d_parent->d_name.name, dentry->d_name.name,
> @@ -383,9 +381,7 @@ const struct address_space_operations nfs_file_aops = {
> .write_end = nfs_write_end,
> .invalidatepage = nfs_invalidate_page,
> .releasepage = nfs_release_page,
> -#ifdef CONFIG_NFS_DIRECTIO
> .direct_IO = nfs_direct_IO,
> -#endif
> .launder_page = nfs_launder_page,
> };
>
> @@ -443,10 +439,8 @@ static ssize_t nfs_file_write(struct kiocb *iocb, const struct iovec *iov,
> ssize_t result;
> size_t count = iov_length(iov, nr_segs);
>
> -#ifdef CONFIG_NFS_DIRECTIO
> if (iocb->ki_filp->f_flags & O_DIRECT)
> return nfs_file_direct_write(iocb, iov, nr_segs, pos);
> -#endif
>
> dfprintk(VFS, "nfs: write(%s/%s(%ld), %[email protected]%Ld)\n",
> dentry->d_parent->d_name.name, dentry->d_name.name,
> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
> index fbe5ba4..13f43d6 100644
> --- a/fs/nfs/internal.h
> +++ b/fs/nfs/internal.h
> @@ -113,13 +113,8 @@ extern void nfs_destroy_readpagecache(void);
> extern int __init nfs_init_writepagecache(void);
> extern void nfs_destroy_writepagecache(void);
>
> -#ifdef CONFIG_NFS_DIRECTIO
> extern int __init nfs_init_directcache(void);
> extern void nfs_destroy_directcache(void);
> -#else
> -#define nfs_init_directcache() (0)
> -#define nfs_destroy_directcache() do {} while(0)
> -#endif
>
> /* nfs2xdr.c */
> extern int nfs_stat_to_errno(int);
>


2008-02-12 22:03:42

by Chuck Lever III

[permalink] [raw]
Subject: Re: [PATCH 01/11] NFS: Always enable NFS direct I/O

On Feb 12, 2008, at 4:03 PM, J. Bruce Fields wrote:
> On Mon, Feb 11, 2008 at 05:11:32PM -0500, Chuck Lever wrote:
>> Since O_DIRECT is a standard feature that is enabled in most distros,
>
> Not all distros? Also, people that really need extremely small
> kernels
> aren't using distro kernels, are they? Or does this not add any
> significant size?

When building the NFS client module on x86_64 with everything else
enabled, but direct I/O disabled, the module is about 3% smaller than
with everything enabled.

Embedded distros can disable NFSv4 and RPCSEC for a much more
significant savings.

>> eliminate the CONFIG_NFS_DIRECTIO build option, and change the
>> fs/nfs/Makefile to always build in the NFS direct I/O engine.
>
>
>>
>> Signed-off-by: Chuck Lever <[email protected]>
>> ---
>>
>> fs/Kconfig | 24 ------------------------
>> fs/nfs/Makefile | 3 +--
>> fs/nfs/file.c | 6 ------
>> fs/nfs/internal.h | 5 -----
>> 4 files changed, 1 insertions(+), 37 deletions(-)
>>
>> diff --git a/fs/Kconfig b/fs/Kconfig
>> index 987b5d7..4965fd8 100644
>> --- a/fs/Kconfig
>> +++ b/fs/Kconfig
>> @@ -1638,30 +1638,6 @@ config NFS_V4
>>
>> If unsure, say N.
>>
>> -config NFS_DIRECTIO
>> - bool "Allow direct I/O on NFS files"
>> - depends on NFS_FS
>> - help
>> - This option enables applications to perform uncached I/O on files
>> - in NFS file systems using the O_DIRECT open() flag. When
>> O_DIRECT
>> - is set for a file, its data is not cached in the system's page
>> - cache. Data is moved to and from user-level application buffers
>> - directly. Unlike local disk-based file systems, NFS O_DIRECT has
>> - no alignment restrictions.
>> -
>> - Unless your program is designed to use O_DIRECT properly, you are
>> - much better off allowing the NFS client to manage data caching
>> for
>> - you. Misusing O_DIRECT can cause poor server performance or
>> network
>> - storms. This kernel build option defaults OFF to avoid exposing
>> - system administrators unwittingly to a potentially hazardous
>> - feature.
>> -
>> - For more details on NFS O_DIRECT, see fs/nfs/direct.c.
>> -
>> - If unsure, say N. This reduces the size of the NFS client, and
>> - causes open() to return EINVAL if a file residing in NFS is
>> - opened with the O_DIRECT flag.
>> -
>> config NFSD
>> tristate "NFS server support"
>> depends on INET
>> diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
>> index f54c4d7..344bccb 100644
>> --- a/fs/nfs/Makefile
>> +++ b/fs/nfs/Makefile
>> @@ -8,7 +8,7 @@ EXTRA_CFLAGS = -W -Wall -Wextra -Wsign-compare \
>> obj-$(CONFIG_NFS_FS) += nfs.o
>>
>> nfs-y := client.o dir.o file.o getroot.o inode.o super.o
>> nfs2xdr.o \
>> - pagelist.o proc.o read.o symlink.o unlink.o \
>> + direct.o pagelist.o proc.o read.o symlink.o unlink.o \
>> write.o namespace.o mount_clnt.o
>> nfs-$(CONFIG_ROOT_NFS) += nfsroot.o
>> nfs-$(CONFIG_NFS_V3) += nfs3proc.o nfs3xdr.o
>> @@ -17,5 +17,4 @@ nfs-$(CONFIG_NFS_V4) += nfs4proc.o nfs4xdr.o
>> nfs4state.o nfs4renewd.o \
>> delegation.o idmap.o \
>> callback.o callback_xdr.o callback_proc.o \
>> nfs4namespace.o
>> -nfs-$(CONFIG_NFS_DIRECTIO) += direct.o
>> nfs-$(CONFIG_SYSCTL) += sysctl.o
>> diff --git a/fs/nfs/file.c b/fs/nfs/file.c
>> index ef57a5a..10e8b80 100644
>> --- a/fs/nfs/file.c
>> +++ b/fs/nfs/file.c
>> @@ -234,10 +234,8 @@ nfs_file_read(struct kiocb *iocb, const
>> struct iovec *iov,
>> ssize_t result;
>> size_t count = iov_length(iov, nr_segs);
>>
>> -#ifdef CONFIG_NFS_DIRECTIO
>> if (iocb->ki_filp->f_flags & O_DIRECT)
>> return nfs_file_direct_read(iocb, iov, nr_segs, pos);
>> -#endif
>>
>> dfprintk(VFS, "nfs: read(%s/%s, %[email protected]%lu)\n",
>> dentry->d_parent->d_name.name, dentry->d_name.name,
>> @@ -383,9 +381,7 @@ const struct address_space_operations
>> nfs_file_aops = {
>> .write_end = nfs_write_end,
>> .invalidatepage = nfs_invalidate_page,
>> .releasepage = nfs_release_page,
>> -#ifdef CONFIG_NFS_DIRECTIO
>> .direct_IO = nfs_direct_IO,
>> -#endif
>> .launder_page = nfs_launder_page,
>> };
>>
>> @@ -443,10 +439,8 @@ static ssize_t nfs_file_write(struct kiocb
>> *iocb, const struct iovec *iov,
>> ssize_t result;
>> size_t count = iov_length(iov, nr_segs);
>>
>> -#ifdef CONFIG_NFS_DIRECTIO
>> if (iocb->ki_filp->f_flags & O_DIRECT)
>> return nfs_file_direct_write(iocb, iov, nr_segs, pos);
>> -#endif
>>
>> dfprintk(VFS, "nfs: write(%s/%s(%ld), %[email protected]%Ld)\n",
>> dentry->d_parent->d_name.name, dentry->d_name.name,
>> diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
>> index fbe5ba4..13f43d6 100644
>> --- a/fs/nfs/internal.h
>> +++ b/fs/nfs/internal.h
>> @@ -113,13 +113,8 @@ extern void nfs_destroy_readpagecache(void);
>> extern int __init nfs_init_writepagecache(void);
>> extern void nfs_destroy_writepagecache(void);
>>
>> -#ifdef CONFIG_NFS_DIRECTIO
>> extern int __init nfs_init_directcache(void);
>> extern void nfs_destroy_directcache(void);
>> -#else
>> -#define nfs_init_directcache() (0)
>> -#define nfs_destroy_directcache() do {} while(0)
>> -#endif
>>
>> /* nfs2xdr.c */
>> extern int nfs_stat_to_errno(int);
>>

--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com