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[PATCH v4 01/26] vfs: Add current_time() api

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current_fs_time() is used for inode timestamps.

Change the signature of the function to take inode pointer
instead of superblock as per Linus's suggestion.

Also, move the api under vfs as per the discussion on the
thread: https://lkml.org/lkml/2016/6/9/36 . As per Arnd's
suggestion on the thread, changing the function name.

current_fs_time() will be deleted after all the references
to it are replaced by current_time().

There was a bug reported by kbuild test bot with the change
as some of the calls to current_time() were made before the
super_block was initialized. Catch these accidental assignments
as timespec_trunc() does for wrong granularities. This allows
for the function to work right even in these circumstances.
But, adds a warning to make the user aware of the bug.

A coccinelle script was used to identify all the current
.alloc_inode super_block callbacks that updated inode timestamps.
proc filesystem was the only one that was modifying inode times
as part of this callback. The series includes a patch to fix that.

Note that timespec_trunc() will also be moved to fs/inode.c
in a separate patch when this will need to be revamped for
bounds checking purposes.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Arnd Bergmann <arnd@arndb.de>
---
 fs/inode.c         | 23 +++++++++++++++++++++++
 include/linux/fs.h |  1 +
 2 files changed, 24 insertions(+)

diff --git a/fs/inode.c b/fs/inode.c
index fd604c0..a95e04e 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2075,3 +2075,26 @@ void inode_nohighmem(struct inode *inode)
 	mapping_set_gfp_mask(inode->i_mapping, GFP_USER);
 }
 EXPORT_SYMBOL(inode_nohighmem);
+
+/**
+ * current_time - Return FS time
+ * @inode: inode.
+ *
+ * Return the current time truncated to the time granularity supported by
+ * the fs.
+ *
+ * Note that inode and inode->sb cannot be NULL.
+ * Otherwise, the function warns and returns time without truncation.
+ */
+struct timespec current_time(struct inode *inode)
+{
+	struct timespec now = current_kernel_time();
+
+	if (unlikely(!inode->i_sb)) {
+		WARN(1, "current_time() called with uninitialized super_block in the inode");
+		return now;
+	}
+
+	return timespec_trunc(now, inode->i_sb->s_time_gran);
+}
+EXPORT_SYMBOL(current_time);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 57a179c..9f81be2d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1470,6 +1470,7 @@ static inline void i_gid_write(struct inode *inode, gid_t gid)
 }
 
 extern struct timespec current_fs_time(struct super_block *sb);
+extern struct timespec current_time(struct inode *inode);
 
 /*
  * Snapshotting support.
-- 
1.9.1

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[GIT PULL] [PATCH v4 00/26] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 10:30 +0200
  [PATCH v4 22/26] libceph: Replace CURRENT_TIME with ktime_get_real_ts Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:30 +0200
  [PATCH v4 05/26] fs: Replace current_fs_time() with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:30 +0200
  [PATCH v4 24/26] fnic: Use time64_t to represent trace timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:30 +0200
  [PATCH v4 13/26] fs: cifs: Replace CURRENT_TIME with ktime_get_real_ts() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:30 +0200
  [PATCH v4 07/26] fs: jfs: Replace CURRENT_TIME_SEC by current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:40 +0200
  [PATCH v4 21/26] block: Replace CURRENT_TIME with ktime_get_real_ts Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:40 +0200
  [PATCH v4 14/26] fs: cifs: Replace CURRENT_TIME by get_seconds Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:40 +0200
  [PATCH v4 06/26] fs: ufs: Use ktime_get_real_ts64() for birthtime Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:40 +0200
  [PATCH v4 20/26] fs: nfs: Make nfs boot time y2038 safe Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:40 +0200
  [PATCH v4 23/26] fs: ceph: Replace current_fs_time for request stamp Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:50 +0200
  [PATCH v4 11/26] fs: udf: Replace CURRENT_TIME with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:50 +0200
  [PATCH v4 09/26] fs: ubifs: Replace CURRENT_TIME_SEC with current_time Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 12:50 +0200
  [PATCH v4 18/26] fs: ocfs2: Replace CURRENT_TIME macro Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:00 +0200
  [PATCH v4 10/26] fs: btrfs: Use ktime_get_real_ts for root ctime Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:00 +0200
    Re: [PATCH v4 10/26] fs: btrfs: Use ktime_get_real_ts for root ctime David Sterba <dsterba@suse.cz> - 2016-08-15 15:30 +0200
  [PATCH v4 17/26] fs: ocfs2: Use time64_t to represent orphan scan times Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:10 +0200
  [PATCH v4 15/26] fs: f2fs: Use ktime_get_real_seconds for sit_info times Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:10 +0200
  [PATCH v4 26/26] time: Delete CURRENT_TIME_SEC and CURRENT_TIME Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:20 +0200
  [PATCH v4 08/26] fs: ext4: Use current_time() for inode timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:20 +0200
  [PATCH v4 02/26] fs: proc: Delete inode time initializations in proc_alloc_inode() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:30 +0200
  [PATCH v4 12/26] fs: cifs: Replace CURRENT_TIME by current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:40 +0200
  [PATCH v4 19/26] audit: Use timespec64 to represent audit timestamps Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:40 +0200
  [PATCH v4 25/26] time: Delete current_fs_time() function Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 13:50 +0200
    Re: [PATCH v4 25/26] time: Delete current_fs_time() function John Stultz <john.stultz@linaro.org> - 2016-08-17 22:10 +0200
  [PATCH v4 16/26] drivers: staging: lustre: Replace CURRENT_TIME with current_time() Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 14:00 +0200
  [PATCH v4 01/26] vfs: Add current_time() api Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-14 16:50 +0200
  Re: [GIT PULL] [PATCH v4 00/26] Delete CURRENT_TIME and  CURRENT_TIME_SEC macros Greg KH <gregkh@linuxfoundation.org> - 2016-08-15 18:30 +0200
    Re: [GIT PULL] [PATCH v4 00/26] Delete CURRENT_TIME and  CURRENT_TIME_SEC macros Deepa Dinamani <deepa.kernel@gmail.com> - 2016-08-16 20:20 +0200
      Re: [GIT PULL] [PATCH v4 00/26] Delete CURRENT_TIME and  CURRENT_TIME_SEC macros Greg KH <gregkh@linuxfoundation.org> - 2016-08-16 21:00 +0200
    Re: [GIT PULL] [PATCH v4 00/26] Delete CURRENT_TIME and CURRENT_TIME_SEC macros Arnd Bergmann <arnd@arndb.de> - 2016-08-23 17:10 +0200

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