Assuming you are referring to the Linux kernel, I ran into the same problem when trying to migrate an old project to 5.10; there was a change made around 4.20 mainline to the kernel time getting mechanism and also a rename of a #define.  I was able to make the following changes and it seems to work okay for me.  (Note: this is obviously not official, just trying to be helpful.)

Dave


@@ -11244,6 +11244,9 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf
 #include <linux/interrupt.h>
 #include <linux/string.h>
 #include <linux/ctype.h>
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(4, 19, 0))
+#include <linux/blkdev.h>
+#endif

 #if (YAFFS_NEW_FOLLOW_LINK == 1)
 #include <linux/namei.h>
@@ -11428,10 +11431,16 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf
 #define update_dir_time(dir) do {\
                (dir)->i_ctime = (dir)->i_mtime = current_kernel_time(); \
        } while (0)
-#else
+#elif (LINUX_VERSION_CODE < KERNEL_VERSION(4,20,0))
 #define update_dir_time(dir) do {\
                (dir)->i_ctime = (dir)->i_mtime = current_kernel_time64(); \
        } while (0)
+#else
+#define update_dir_time(dir) do {\
+               struct timespec64 ltime; \
+               ktime_get_coarse_real_ts64(&ltime); \
+               (dir)->i_ctime = (dir)->i_mtime = ltime; \
+       } while (0)
 #endif

 #if (LINUX_VERSION_CODE < KERNEL_VERSION(4, 9, 0))
@@ -13202,7 +13211,17 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf
 #if (LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 19))
                inode->i_blksize = inode->i_sb->s_blocksize;
 #endif
-#if (LINUX_VERSION_CODE > KERNEL_VERSION(2, 5, 0))
+#if (LINUX_VERSION_CODE > KERNEL_VERSION(4, 19, 0))
+
+               inode->i_rdev = old_decode_dev(obj->yst_rdev);
+               inode->i_atime.tv_sec = (time64_t) (obj->yst_atime);
+               inode->i_atime.tv_nsec = 0;
+               inode->i_mtime.tv_sec = (time64_t) obj->yst_mtime;
+               inode->i_mtime.tv_nsec = 0;
+               inode->i_ctime.tv_sec = (time64_t) obj->yst_ctime;
+               inode->i_ctime.tv_nsec = 0;
+
+#elif (LINUX_VERSION_CODE > KERNEL_VERSION(2, 5, 0))

                inode->i_rdev = old_decode_dev(obj->yst_rdev);
                inode->i_atime.tv_sec = (time_t) (obj->yst_atime);
@@ -13894,12 +13914,12 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf
                return 1;
        }

-       read_only = ((*flags & MS_RDONLY) != 0);
+       read_only = ((*flags & SB_RDONLY) != 0);
        if (!read_only && !(mtd->flags & MTD_WRITEABLE)) {
                read_only = 1;
                printk(KERN_INFO
                        "yaffs: mtd is read only, setting superblock read only");
-               *flags |= MS_RDONLY;
+               *flags |= SB_RDONLY;
        }

        dev = sb->s_fs_info;
@@ -14061,9 +14081,9 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf

        sb->s_magic = YAFFS_MAGIC;
        sb->s_op = &yaffs_super_ops;
-       sb->s_flags |= MS_NOATIME;
+       sb->s_flags |= SB_NOATIME;

-       read_only = ((sb->s_flags & MS_RDONLY) != 0);
+       read_only = ((sb->s_flags & SB_RDONLY) != 0);

 #ifdef YAFFS_COMPILE_EXPORTFS
        sb->s_export_op = &yaffs_export_ops;
@@ -14141,7 +14161,7 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yaffs_vfs.c fs/yaffs2/yaf
                printk(KERN_INFO
                       "yaffs: mtd is read only, setting superblock read only\n"
                );
-               sb->s_flags |= MS_RDONLY;
+               sb->s_flags |= SB_RDONLY;
        }

        dev = kmalloc(sizeof(struct yaffs_dev), GFP_KERNEL);
@@ -17228,8 +17248,10 @@ diff -Naur ../../../../../archive/linux-omap/fs/yaffs2/yportenv.h fs/yaffs2/ypor
 #if (LINUX_VERSION_CODE > KERNEL_VERSION(2, 5, 0))
 #if (LINUX_VERSION_CODE < KERNEL_VERSION(4,12,0))
 #define Y_CURRENT_TIME CURRENT_TIME.tv_sec
-#else
+#elif (LINUX_VERSION_CODE < KERNEL_VERSION(4,20,0))
 #define Y_CURRENT_TIME current_kernel_time().tv_sec
+#else
+#define Y_CURRENT_TIME ({struct timespec64 retval; ktime_get_coarse_real_ts64(&retval); retval.tv_sec;})
 #endif
 #define Y_TIME_CONVERT(x) (x).tv_sec
 #else






> On Aug 3, 2021, at 11:12 PM, R Y <averybigant@gmail.com> wrote:
> 
> I have been following the Building Yaffs into Linux tutorial to try to integrate yaffs2 into linux kernel 5.10. However, I have encountered multiple errors during compilation. It seems some break changes in newer kernels (>5.0 and especially >5.6) cause these errors. To name a few, the current_kernel_time64 function is deprecated and we should use SB_* instead of MS_* (MS_RDONLY, MS_NOATIME, etc.)
> 
> I am wondering what's the latest version of kernel supported by yaffs2? Am I missing something?
> 
> Thanks!
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