diff options
| -rw-r--r-- | fs/inode.c | 82 | ||||
| -rw-r--r-- | fs/stat.c | 41 | ||||
| -rw-r--r-- | include/linux/fs.h | 46 |
3 files changed, 162 insertions, 7 deletions
diff --git a/fs/inode.c b/fs/inode.c index e50d94a136fe..f55957ac80e6 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -2118,10 +2118,52 @@ int file_remove_privs(struct file *file) } EXPORT_SYMBOL(file_remove_privs); +/** + * current_mgtime - Return FS time (possibly fine-grained) + * @inode: inode. + * + * Return the current time truncated to the time granularity supported by + * the fs, as suitable for a ctime/mtime change. If the ctime is flagged + * as having been QUERIED, get a fine-grained timestamp. + */ +struct timespec64 current_mgtime(struct inode *inode) +{ + struct timespec64 now, ctime; + atomic_long_t *pnsec = (atomic_long_t *)&inode->__i_ctime.tv_nsec; + long nsec = atomic_long_read(pnsec); + + if (nsec & I_CTIME_QUERIED) { + ktime_get_real_ts64(&now); + return timestamp_truncate(now, inode); + } + + ktime_get_coarse_real_ts64(&now); + now = timestamp_truncate(now, inode); + + /* + * If we've recently fetched a fine-grained timestamp + * then the coarse-grained one may still be earlier than the + * existing ctime. Just keep the existing value if so. + */ + ctime = inode_get_ctime(inode); + if (timespec64_compare(&ctime, &now) > 0) + now = ctime; + + return now; +} +EXPORT_SYMBOL(current_mgtime); + +static struct timespec64 current_ctime(struct inode *inode) +{ + if (is_mgtime(inode)) + return current_mgtime(inode); + return current_time(inode); +} + static int inode_needs_update_time(struct inode *inode) { int sync_it = 0; - struct timespec64 now = current_time(inode); + struct timespec64 now = current_ctime(inode); struct timespec64 ctime; /* First try to exhaust all avenues to not sync */ @@ -2552,9 +2594,43 @@ EXPORT_SYMBOL(current_time); */ struct timespec64 inode_set_ctime_current(struct inode *inode) { - struct timespec64 now = current_time(inode); + struct timespec64 now; + struct timespec64 ctime; + + ctime.tv_nsec = READ_ONCE(inode->__i_ctime.tv_nsec); + if (!(ctime.tv_nsec & I_CTIME_QUERIED)) { + now = current_time(inode); - inode_set_ctime(inode, now.tv_sec, now.tv_nsec); + /* Just copy it into place if it's not multigrain */ + if (!is_mgtime(inode)) { + inode_set_ctime_to_ts(inode, now); + return now; + } + + /* + * If we've recently updated with a fine-grained timestamp, + * then the coarse-grained one may still be earlier than the + * existing ctime. Just keep the existing value if so. + */ + ctime.tv_sec = inode->__i_ctime.tv_sec; + if (timespec64_compare(&ctime, &now) > 0) + return ctime; + + /* + * Ctime updates are usually protected by the inode_lock, but + * we can still race with someone setting the QUERIED flag. + * Try to swap the new nsec value into place. If it's changed + * in the interim, then just go with a fine-grained timestamp. + */ + if (cmpxchg(&inode->__i_ctime.tv_nsec, ctime.tv_nsec, + now.tv_nsec) != ctime.tv_nsec) + goto fine_grained; + inode->__i_ctime.tv_sec = now.tv_sec; + return now; + } +fine_grained: + ktime_get_real_ts64(&now); + inode_set_ctime_to_ts(inode, timestamp_truncate(now, inode)); return now; } EXPORT_SYMBOL(inode_set_ctime_current); diff --git a/fs/stat.c b/fs/stat.c index 7644e5997035..136711ae72fb 100644 --- a/fs/stat.c +++ b/fs/stat.c @@ -27,6 +27,37 @@ #include "mount.h" /** + * fill_mg_cmtime - Fill in the mtime and ctime and flag ctime as QUERIED + * @stat: where to store the resulting values + * @request_mask: STATX_* values requested + * @inode: inode from which to grab the c/mtime + * + * Given @inode, grab the ctime and mtime out if it and store the result + * in @stat. When fetching the value, flag it as queried so the next write + * will use a fine-grained timestamp. + */ +void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode) +{ + atomic_long_t *pnsec = (atomic_long_t *)&inode->__i_ctime.tv_nsec; + + /* If neither time was requested, then don't report them */ + if (!(request_mask & (STATX_CTIME|STATX_MTIME))) { + stat->result_mask &= ~(STATX_CTIME|STATX_MTIME); + return; + } + + stat->mtime = inode->i_mtime; + stat->ctime.tv_sec = inode->__i_ctime.tv_sec; + /* + * Atomically set the QUERIED flag and fetch the new value with + * the flag masked off. + */ + stat->ctime.tv_nsec = atomic_long_fetch_or(I_CTIME_QUERIED, pnsec) & + ~I_CTIME_QUERIED; +} +EXPORT_SYMBOL(fill_mg_cmtime); + +/** * generic_fillattr - Fill in the basic attributes from the inode struct * @idmap: idmap of the mount the inode was found from * @request_mask: statx request_mask @@ -58,8 +89,14 @@ void generic_fillattr(struct mnt_idmap *idmap, u32 request_mask, stat->rdev = inode->i_rdev; stat->size = i_size_read(inode); stat->atime = inode->i_atime; - stat->mtime = inode->i_mtime; - stat->ctime = inode_get_ctime(inode); + + if (is_mgtime(inode)) { + fill_mg_cmtime(stat, request_mask, inode); + } else { + stat->mtime = inode->i_mtime; + stat->ctime = inode_get_ctime(inode); + } + stat->blksize = i_blocksize(inode); stat->blocks = inode->i_blocks; diff --git a/include/linux/fs.h b/include/linux/fs.h index a83313f90fe3..455835d0e963 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1474,18 +1474,47 @@ static inline bool fsuidgid_has_mapping(struct super_block *sb, kgid_has_mapping(fs_userns, kgid); } +struct timespec64 current_mgtime(struct inode *inode); struct timespec64 current_time(struct inode *inode); struct timespec64 inode_set_ctime_current(struct inode *inode); +/* + * Multigrain timestamps + * + * Conditionally use fine-grained ctime and mtime timestamps when there + * are users actively observing them via getattr. The primary use-case + * for this is NFS clients that use the ctime to distinguish between + * different states of the file, and that are often fooled by multiple + * operations that occur in the same coarse-grained timer tick. + * + * The kernel always keeps normalized struct timespec64 values in the ctime, + * which means that only the first 30 bits of the value are used. Use the + * 31st bit of the ctime's tv_nsec field as a flag to indicate that the value + * has been queried since it was last updated. + */ +#define I_CTIME_QUERIED (1L<<30) + /** * inode_get_ctime - fetch the current ctime from the inode * @inode: inode from which to fetch ctime * - * Grab the current ctime from the inode and return it. + * Grab the current ctime tv_nsec field from the inode, mask off the + * I_CTIME_QUERIED flag and return it. This is mostly intended for use by + * internal consumers of the ctime that aren't concerned with ensuring a + * fine-grained update on the next change (e.g. when preparing to store + * the value in the backing store for later retrieval). + * + * This is safe to call regardless of whether the underlying filesystem + * is using multigrain timestamps. */ static inline struct timespec64 inode_get_ctime(const struct inode *inode) { - return inode->__i_ctime; + struct timespec64 ctime; + + ctime.tv_sec = inode->__i_ctime.tv_sec; + ctime.tv_nsec = inode->__i_ctime.tv_nsec & ~I_CTIME_QUERIED; + + return ctime; } /** @@ -2259,6 +2288,7 @@ struct file_system_type { #define FS_USERNS_MOUNT 8 /* Can be mounted by userns root */ #define FS_DISALLOW_NOTIFY_PERM 16 /* Disable fanotify permission events */ #define FS_ALLOW_IDMAP 32 /* FS has been updated to handle vfs idmappings. */ +#define FS_MGTIME 64 /* FS uses multigrain timestamps */ #define FS_RENAME_DOES_D_MOVE 32768 /* FS will handle d_move() during rename() internally. */ int (*init_fs_context)(struct fs_context *); const struct fs_parameter_spec *parameters; @@ -2282,6 +2312,17 @@ struct file_system_type { #define MODULE_ALIAS_FS(NAME) MODULE_ALIAS("fs-" NAME) +/** + * is_mgtime: is this inode using multigrain timestamps + * @inode: inode to test for multigrain timestamps + * + * Return true if the inode uses multigrain timestamps, false otherwise. + */ +static inline bool is_mgtime(const struct inode *inode) +{ + return inode->i_sb->s_type->fs_flags & FS_MGTIME; +} + extern struct dentry *mount_bdev(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, int (*fill_super)(struct super_block *, void *, int)); @@ -2918,6 +2959,7 @@ extern void page_put_link(void *); extern int page_symlink(struct inode *inode, const char *symname, int len); extern const struct inode_operations page_symlink_inode_operations; extern void kfree_link(void *); +void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode); void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *); void generic_fill_statx_attr(struct inode *inode, struct kstat *stat); extern int vfs_getattr_nosec(const struct path *, struct kstat *, u32, unsigned int); |