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vfs: Add timestamp_truncate() api 

timespec_trunc() function is used to truncate a
filesystem timestamp to the right granularity.
But, the function does not clamp tv_sec part of the
timestamps according to the filesystem timestamp limits.

The replacement api: timestamp_truncate() also alters the
signature of the function to accommodate filesystem
timestamp clamping according to flesystem limits.

Note that the tv_nsec part is set to 0 if tv_sec is not within
the range supported for the filesystem.

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Acked-by: Jeff Layton <jlayton@kernel.org>
This commit is contained in:
Deepa Dinamani 2018-01-21 18:04:25 -08:00
parent 188d20bcd1
commit 50e17c000c
2 changed files with 34 additions and 1 deletions
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33
fs/inode.c
View File

@ -2166,6 +2166,37 @@ struct timespec64 timespec64_trunc(struct timespec64 t, unsigned gran)
}
EXPORT_SYMBOL(timespec64_trunc);
/**
* timestamp_truncate - Truncate timespec to a granularity
* @t: Timespec
* @inode: inode being updated
*
* Truncate a timespec to the granularity supported by the fs
* containing the inode. Always rounds down. gran must
* not be 0 nor greater than a second (NSEC_PER_SEC, or 10^9 ns).
*/
struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode)
{
struct super_block *sb = inode->i_sb;
unsigned int gran = sb->s_time_gran;
t.tv_sec = clamp(t.tv_sec, sb->s_time_min, sb->s_time_max);
if (unlikely(t.tv_sec == sb->s_time_max || t.tv_sec == sb->s_time_min))
t.tv_nsec = 0;
/* Avoid division in the common cases 1 ns and 1 s. */
if (gran == 1)
; /* nothing */
else if (gran == NSEC_PER_SEC)
t.tv_nsec = 0;
else if (gran > 1 && gran < NSEC_PER_SEC)
t.tv_nsec -= t.tv_nsec % gran;
else
WARN(1, "invalid file time granularity: %u", gran);
return t;
}
EXPORT_SYMBOL(timestamp_truncate);
/**
* current_time - Return FS time
* @inode: inode.
@ -2187,7 +2218,7 @@ struct timespec64 current_time(struct inode *inode)
return now;
}
return timespec64_trunc(now, inode->i_sb->s_time_gran);
return timestamp_truncate(now, inode);
}
EXPORT_SYMBOL(current_time);

2
include/linux/fs.h
View File

@ -726,6 +726,8 @@ struct inode {
void *i_private; /* fs or device private pointer */
} __randomize_layout;
struct timespec64 timestamp_truncate(struct timespec64 t, struct inode *inode);
static inline unsigned int i_blocksize(const struct inode *node)
{
return (1 << node->i_blkbits);