This is a preparation patch to add range checking for inode timestamps. These range checks will be used to clamp timestamps to filesystem allowed ranges. Individual filesystems do not have the same on disk format as the in memory inodes. Range checking and clamping times assigned to inodes will help keep in memory and on-disk timestamps to be in sync. Extend struct super_block to include information about the max and min inode times each filesystem can hold. These are dependent on the on-disk format of filesystems. Every time a new superblock is created, make sure that the superblock max and min timestamp fields are assigned invalid values. Another series will initialize these fields to appropriate values for every filesystem. The values are currently ignored. The exact policy and behavior will be decided in a separate patch. MAX_INVALID_VFS_TIME and MIN_INVALID_VFS_TIME are initialized to S64_MIN and S64_MAX respectively so that even if one of the fields is uninitialized, it can be detected by using the condition max_time < min_time. The original idea for the feature comes from the discussion: https://lkml.org/lkml/2014/5/30/669 Signed-off-by: Deepa Dinamani <deepa.kernel@xxxxxxxxx> --- The intention is to include this as part of 4.6 so that the follow on patches can go into 4.7. The series and the plan have been discussed with Arnd Bergmann. fs/super.c | 2 ++ include/linux/fs.h | 13 ++++++++++++- 2 files changed, 14 insertions(+), 1 deletion(-) diff --git a/fs/super.c b/fs/super.c index 1182af8..d70a8f6 100644 --- a/fs/super.c +++ b/fs/super.c @@ -239,6 +239,8 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags) s->s_maxbytes = MAX_NON_LFS; s->s_op = &default_op; s->s_time_gran = 1000000000; + s->s_time_max = MAX_INVALID_VFS_TIME; + s->s_time_min = MIN_INVALID_VFS_TIME; s->cleancache_poolid = CLEANCACHE_NO_POOL; s->s_shrink.seeks = DEFAULT_SEEKS; diff --git a/include/linux/fs.h b/include/linux/fs.h index 1af4727..15b41e6 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -927,6 +927,12 @@ static inline struct file *get_file(struct file *f) #define MAX_LFS_FILESIZE ((loff_t)0x7fffffffffffffffLL) #endif +#define MAX_VFS_TIME S64_MAX +#define MIN_VFS_TIME S64_MIN + +#define MAX_INVALID_VFS_TIME S64_MIN +#define MIN_INVALID_VFS_TIME S64_MAX + #define FL_POSIX 1 #define FL_FLOCK 2 #define FL_DELEG 4 /* NFSv4 delegation */ @@ -1343,7 +1349,12 @@ struct super_block { /* Granularity of c/m/atime in ns. Cannot be worse than a second */ - u32 s_time_gran; + u32 s_time_gran; + /* Max and min values for timestamps + * according to the range supported by filesystems. + */ + time64_t s_time_max; + time64_t s_time_min; /* * The next field is for VFS *only*. No filesystems have any business -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
