[yocto] [PATCH 1/1] mm: msync: fix the behaviour msync on tmpfs

[zumeng.chen]

This patch has been validated by the following commands
on both CPUs with or without cache alias, which is for

http://bugzilla.pokylinux.org/show_bug.cgi?id=1429

root at routerstationpro:~# dmesg|grep alias
Primary data cache 32kB, 4-way, VIPT, cache aliases, linesize 32 bytes
root at routerstationpro:~# for i in `seq 1 1000`; do ./msync01 ;done


root at localhost:/tmp> dmesg|grep alias
Primary data cache 32kB, 4-way, PIPT, no aliases, linesize 32 bytes
root at localhost:/tmp> zcat /proc/config.gz |grep WINPATH
CONFIG_WINTEGRA_WINPATH=y
CONFIG_WINTEGRA_WINPATH3=y
CONFIG_SERIAL_8250_WINPATH=y
root at localhost:/tmp> for i in `seq 1 1000`; do ./msync01 ;done

Passed.

On 2011年12月21日 23:17, Zumeng Chen wrote:
> For tmpfs, no matter which flag(ASYNC or SYNC) gets from msync,
> there is not so much thing to do for CPUs without cache alias,
> But for some CPUs with cache alias, msync has to flush cache
> explicitly, which makes sure the data coherency between memory
> file and cache.
>
> Signed-off-by: Zumeng Chen<zumeng.chen at windriver.com>
> ---
>   include/linux/mm.h |    1 +
>   mm/msync.c         |   20 +++++++++++++++++++-
>   mm/shmem.c         |    5 +++++
>   3 files changed, 25 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index f59179b..858db90 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -868,6 +868,7 @@ extern void pagefault_out_of_memory(void);
>   extern void show_free_areas(unsigned int flags);
>   extern bool skip_free_areas_node(unsigned int flags, int nid);
>
> +int is_shmem_file(struct file *file);
>   int shmem_lock(struct file *file, int lock, struct user_struct *user);
>   struct file *shmem_file_setup(const char *name, loff_t size, unsigned long flags);
>   void shmem_set_file(struct vm_area_struct *vma, struct file *file);
> diff --git a/mm/msync.c b/mm/msync.c
> index 632df45..2f0d8fa 100644
> --- a/mm/msync.c
> +++ b/mm/msync.c
> @@ -13,6 +13,7 @@
>   #include<linux/file.h>
>   #include<linux/syscalls.h>
>   #include<linux/sched.h>
> +#include<asm/cacheflush.h>
>
>   /*
>    * MS_SYNC syncs the entire file - including mappings.
> @@ -33,6 +34,7 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
>   	unsigned long end;
>   	struct mm_struct *mm = current->mm;
>   	struct vm_area_struct *vma;
> +	struct file *file;
>   	int unmapped_error = 0;
>   	int error = -EINVAL;
>
> @@ -56,8 +58,24 @@ SYSCALL_DEFINE3(msync, unsigned long, start, size_t, len, int, flags)
>   	 */
>   	down_read(&mm->mmap_sem);
>   	vma = find_vma(mm, start);
> +
> +#ifdef CONFIG_TMPFS
> +	/*
> +	 * For tmpfs, no matter which flag(ASYNC or SYNC) gets from msync,
> +	 * there is not so much thing to do for CPUs without cache alias,
> +	 * But for some CPUs with cache alias, msync has to flush cache
> +	 * explicitly, which makes sure the data coherency between memory
> +	 * file and cache.
> +	 */
> +	file =  vma->vm_file;
> +	if (is_shmem_file(file)) {
> +		flush_cache_range(vma, start, start+len);
> +		error = 0;
> +		goto out_unlock;
> +	}
> +#endif
> +
>   	for (;;) {
> -		struct file *file;
>
>   		/* Still start<  end. */
>   		error = -ENOMEM;
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 92e5c15..4fabfac 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2793,6 +2793,11 @@ static struct file_system_type tmpfs_fs_type = {
>   	.kill_sb	= kill_litter_super,
>   };
>
> +int is_shmem_file(struct file *file)
> +{
> +	return (file->f_op ==&shmem_file_operations)? 1 : 0;
> +}
> +
>   int __init init_tmpfs(void)
>   {
>   	int error;