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Date: Fri, 5 Dec 2008 13:18:30 +0000 (GMT)
From: Hugh Dickins <hugh@...itas.com>
To: Matt Mackall <mpm@...enic.com>
cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] shmem: unify regular and tiny shmem
On Thu, 4 Dec 2008, Matt Mackall wrote:
> tiny-shmem shares most of its 130 lines of code with shmem and tends
> to break when particular bits of shmem get modified. Unifying saves
> code and makes keeping these two in sync much easier.
>
> before:
> 14367 392 24 14783 39bf mm/shmem.o
> 396 72 8 476 1dc mm/tiny-shmem.o
>
> after:
> 14367 392 24 14783 39bf mm/shmem.o
> 412 72 8 492 1ec mm/shmem.o tiny
>
> Signed-off-by: Matt Mackall <mpm@...enic.com>
I agree with where you're going (surrendering your empire to mine!
or perhaps you don't you see it quite that way?), but I think this
isn't quite the patch you meant to send: it shouldn't contain that
> - &shmem_file_operations);
> + &shmem_file_operations);
> +
> +#ifndef CONFIG_MMU
> + error = ramfs_nommu_expand_for_mapping(inode, size);
> + if (error)
> + goto close_file;
> +#endif
hunk in mm/shmem.c, and it should be deleting mm/tiny-shmem.c?
Hugh
> diff -r 8a9f1e9c46e8 -r 3fd7e399e034 init/Kconfig
> --- a/init/Kconfig Mon Oct 27 17:33:21 2008 -0500
> +++ b/init/Kconfig Mon Oct 27 17:33:24 2008 -0500
> @@ -830,10 +830,6 @@
> boolean
> select PLIST
>
> -config TINY_SHMEM
> - default !SHMEM
> - bool
> -
> config BASE_SMALL
> int
> default 0 if BASE_FULL
> diff -r 8a9f1e9c46e8 -r 3fd7e399e034 mm/Makefile
> --- a/mm/Makefile Mon Oct 27 17:33:21 2008 -0500
> +++ b/mm/Makefile Mon Oct 27 17:33:24 2008 -0500
> @@ -9,7 +9,7 @@
>
> obj-y := bootmem.o filemap.o mempool.o oom_kill.o fadvise.o \
> maccess.o page_alloc.o page-writeback.o pdflush.o \
> - readahead.o swap.o truncate.o vmscan.o \
> + readahead.o swap.o truncate.o vmscan.o shmem.o \
> prio_tree.o util.o mmzone.o vmstat.o backing-dev.o \
> page_isolation.o mm_init.o $(mmu-y)
>
> @@ -21,9 +21,7 @@
> obj-$(CONFIG_NUMA) += mempolicy.o
> obj-$(CONFIG_SPARSEMEM) += sparse.o
> obj-$(CONFIG_SPARSEMEM_VMEMMAP) += sparse-vmemmap.o
> -obj-$(CONFIG_SHMEM) += shmem.o
> obj-$(CONFIG_TMPFS_POSIX_ACL) += shmem_acl.o
> -obj-$(CONFIG_TINY_SHMEM) += tiny-shmem.o
> obj-$(CONFIG_SLOB) += slob.o
> obj-$(CONFIG_MMU_NOTIFIER) += mmu_notifier.o
> obj-$(CONFIG_SLAB) += slab.o
> diff -r 8a9f1e9c46e8 -r 3fd7e399e034 mm/shmem.c
> --- a/mm/shmem.c Mon Oct 27 17:33:21 2008 -0500
> +++ b/mm/shmem.c Mon Oct 27 17:33:24 2008 -0500
> @@ -14,31 +14,39 @@
> * Copyright (c) 2004, Luke Kenneth Casson Leighton <lkcl@...l.net>
> * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@...hat.com>
> *
> + * tiny-shmem:
> + * Copyright (c) 2004, 2008 Matt Mackall <mpm@...enic.com>
> + *
> * This file is released under the GPL.
> */
>
> +#include <linux/fs.h>
> +#include <linux/init.h>
> +#include <linux/vfs.h>
> +#include <linux/mount.h>
> +#include <linux/file.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/swap.h>
> +
> +static struct vfsmount *shm_mnt;
> +
> +#ifdef CONFIG_SHMEM
> /*
> * This virtual memory filesystem is heavily based on the ramfs. It
> * extends ramfs by the ability to use swap and honor resource limits
> * which makes it a completely usable filesystem.
> */
>
> -#include <linux/module.h>
> -#include <linux/init.h>
> -#include <linux/fs.h>
> #include <linux/xattr.h>
> #include <linux/exportfs.h>
> #include <linux/generic_acl.h>
> -#include <linux/mm.h>
> #include <linux/mman.h>
> -#include <linux/file.h>
> -#include <linux/swap.h>
> #include <linux/pagemap.h>
> #include <linux/string.h>
> #include <linux/slab.h>
> #include <linux/backing-dev.h>
> #include <linux/shmem_fs.h>
> -#include <linux/mount.h>
> #include <linux/writeback.h>
> #include <linux/vfs.h>
> #include <linux/blkdev.h>
> @@ -2486,7 +2494,6 @@
> .get_sb = shmem_get_sb,
> .kill_sb = kill_litter_super,
> };
> -static struct vfsmount *shm_mnt;
>
> static int __init init_tmpfs(void)
> {
> @@ -2525,7 +2532,51 @@
> shm_mnt = ERR_PTR(error);
> return error;
> }
> -module_init(init_tmpfs)
> +
> +#else /* !CONFIG_SHMEM */
> +
> +/*
> + * tiny-shmem: simple shmemfs and tmpfs using ramfs code
> + *
> + * This is intended for small system where the benefits of the full
> + * shmem code (swap-backed and resource-limited) are outweighed by
> + * their complexity. On systems without swap this code should be
> + * effectively equivalent, but much lighter weight.
> + */
> +
> +#include <linux/ramfs.h>
> +
> +static struct file_system_type tmpfs_fs_type = {
> + .name = "tmpfs",
> + .get_sb = ramfs_get_sb,
> + .kill_sb = kill_litter_super,
> +};
> +
> +static int __init init_tmpfs(void)
> +{
> + BUG_ON(register_filesystem(&tmpfs_fs_type) != 0);
> +
> + shm_mnt = kern_mount(&tmpfs_fs_type);
> + BUG_ON(IS_ERR(shm_mnt));
> +
> + return 0;
> +}
> +
> +int shmem_unuse(swp_entry_t entry, struct page *page)
> +{
> + return 0;
> +}
> +
> +#define shmem_file_operations ramfs_file_operations
> +#define shmem_vm_ops generic_file_vm_ops
> +#define shmem_get_inode ramfs_get_inode
> +#define shmem_acct_size(a, b) 0
> +#define shmem_unacct_size(a, b) do {} while (0)
> +#define SHMEM_MAX_BYTES LLONG_MAX
> +
> +#endif /* CONFIG_SHMEM */
> +
> +/* common code */
>
> /**
> * shmem_file_setup - get an unlinked file living in tmpfs
> @@ -2569,12 +2620,20 @@
> if (!inode)
> goto close_file;
>
> +#ifdef CONFIG_SHMEM
> SHMEM_I(inode)->flags = flags & VM_ACCOUNT;
> +#endif
> d_instantiate(dentry, inode);
> inode->i_size = size;
> inode->i_nlink = 0; /* It is unlinked */
> init_file(file, shm_mnt, dentry, FMODE_WRITE | FMODE_READ,
> - &shmem_file_operations);
> + &shmem_file_operations);
> +
> +#ifndef CONFIG_MMU
> + error = ramfs_nommu_expand_for_mapping(inode, size);
> + if (error)
> + goto close_file;
> +#endif
> return file;
>
> close_file:
> @@ -2606,3 +2665,5 @@
> vma->vm_ops = &shmem_vm_ops;
> return 0;
> }
> +
> +module_init(init_tmpfs)
>
> --
> Mathematics is the supreme nostalgia of our time.
--
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