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shmem: use monotonic time for i_generation

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get_seconds() is deprecated because it will lead to a 32-bit overflow in
2038 or 2106.  We don't need the i_generation to be strictly monotonic
anyway, and other file systems like ext4 and xfs just use prandom_u32(),
so let's use the same one here.

If this is considered too slow, we could also use ktime_get_seconds() or
ktime_get_real_seconds() to keep the previous behavior.  Both of these
return a time64_t and are not deprecated, but only return a unique value
once per second, and are predictable.

Link: http://lkml.kernel.org/r/20180620082556.581543-1-arnd@arndb.de
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arnd Bergmann 2018-08-17 15:45:09 -07:00 committed by Linus Torvalds
parent d6a24df006
commit 46c9a946d7
1 changed files with 2 additions and 1 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

3
mm/shmem.c
View file

@ -29,6 +29,7 @@
#include <linux/pagemap.h> #include <linux/pagemap.h>
#include <linux/file.h> #include <linux/file.h>
#include <linux/mm.h> #include <linux/mm.h>
#include <linux/random.h>
#include <linux/sched/signal.h> #include <linux/sched/signal.h>
#include <linux/export.h> #include <linux/export.h>
#include <linux/swap.h> #include <linux/swap.h>
@ -2188,7 +2189,7 @@ static struct inode *shmem_get_inode(struct super_block *sb, const struct inode
inode_init_owner(inode, dir, mode); inode_init_owner(inode, dir, mode);
inode->i_blocks = 0; inode->i_blocks = 0;
inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
inode->i_generation = get_seconds(); inode->i_generation = prandom_u32();
info = SHMEM_I(inode); info = SHMEM_I(inode);
memset(info, 0, (char *)inode - (char *)info); memset(info, 0, (char *)inode - (char *)info);
spin_lock_init(&info->lock); spin_lock_init(&info->lock);