[yocto] [V2 PATCH 1/1] mm: msync: fix issues of sys_msync on tmpfs

[Khem Raj]

On (22/12/11 09:24), Bruce Ashfield wrote:
> On 11-12-21 10:07 PM, Zumeng Chen wrote:
> >There are two problems as follows shown:
> >1 ) for TMPFS, nothing need to be done in sys_msync,
> >     sys_msync just return 0 for all arches.
> >
> >2 ) But for MIPS CPUs with cache alias(dmesg|grep alias),
> >     it maybe has the issue, which reported by msync test
> >     suites in ltp-full, when the memory of memset used by
> >     msycn01 has cache alias.
> >     So, in this situation, we have to flush the related
> >     vma to make sure correct read.
> 
> Looks good. I'll queue this for the next kernel update.
> 


has this been proposed to lkml ?

> Cheers,
> 
> Bruce
> 
> >
> >Signed-off-by: Zumeng Chen<zumeng.chen at windriver.com>
> >---
> >  include/linux/shmem_fs.h |   10 ++++++++++
> >  mm/msync.c               |   22 +++++++++++++++++++++-
> >  mm/shmem.c               |    5 +++++
> >  3 files changed, 36 insertions(+), 1 deletions(-)
> >
> >diff --git a/include/linux/shmem_fs.h b/include/linux/shmem_fs.h
> >index aa08fa8..62a2d57 100644
> >--- a/include/linux/shmem_fs.h
> >+++ b/include/linux/shmem_fs.h
> >@@ -12,6 +12,15 @@
> >
> >  #define SHMEM_SYMLINK_INLINE_LEN (SHMEM_NR_DIRECT * sizeof(swp_entry_t))
> >
> >+/*
> >+
> >+*/
> >+#ifndef cpu_has_dc_aliases
> >+#define CPU_HAS_CACHE_ALIAS 0
> >+#else
> >+#define CPU_HAS_CACHE_ALIAS cpu_has_dc_aliases
> >+#endif
> >+
> >  struct shmem_inode_info {
> >  	spinlock_t		lock;
> >  	unsigned long		flags;
> >@@ -49,6 +58,7 @@ static inline struct shmem_inode_info *SHMEM_I(struct inode *inode)
> >  /*
> >   * Functions in mm/shmem.c called directly from elsewhere:
> >   */
> >+extern int is_shmem_file(struct file *file);
> >  extern int init_tmpfs(void);
> >  extern int shmem_fill_super(struct super_block *sb, void *data, int silent);
> >  extern struct file *shmem_file_setup(const char *name,
> >diff --git a/mm/msync.c b/mm/msync.c
> >index 632df45..84cb068 100644
> >--- a/mm/msync.c
> >+++ b/mm/msync.c
> >@@ -13,6 +13,8 @@
> >  #include<linux/file.h>
> >  #include<linux/syscalls.h>
> >  #include<linux/sched.h>
> >+#include<linux/shmem_fs.h>
> >+#include<asm/cacheflush.h>
> >
> >  /*
> >   * MS_SYNC syncs the entire file - including mappings.
> >@@ -33,6 +35,7 @@ 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 +59,25 @@ 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)) {
> >+		if(CPU_HAS_CACHE_ALIAS)
> >+			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;
> 
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-- 
-Khem