From: Robin H. Johnson Date: Mon, 12 Jun 2006 20:50:25 +0000 (+0100) Subject: [PATCH] tmpfs: time granularity fix for [acm]time going backwards X-Git-Tag: v2.6.17~18 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=cfd95a9cf58cd9e92d4c23b5ee20b07a3d121477;p=linux-2.6 [PATCH] tmpfs: time granularity fix for [acm]time going backwards I noticed a strange behavior in a tmpfs file system the other day, while building packages - occasionally, and seemingly at random, make decided to rebuild a target. However, only on tmpfs. A file would be created, and if checked, it had a sub-second timestamp. However, after an utimes related call where sub-seconds should be set, they were zeroed instead. In the case that a file was created, and utimes(...,NULL) was used on it in the same second, the timestamp on the file moved backwards. After some digging, I found that this was being caused by tmpfs not having a time granularity set, thus inheriting the default 1 second granularity. Hugh adds: yes, we missed tmpfs when the s_time_gran mods went into 2.6.11. Unfortunately, the granularity of CURRENT_TIME, often used in filesystems, does not match the default granularity set by alloc_super. A few more such discrepancies have been found, but this is the most important to fix now. Signed-off-by: Robin H. Johnson Acked-by: Andi Kleen Signed-off-by: Hugh Dickins Signed-off-by: Linus Torvalds --- diff --git a/mm/shmem.c b/mm/shmem.c index 4c5e68e4e9..73f7a9dfcd 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2102,6 +2102,7 @@ static int shmem_fill_super(struct super_block *sb, sb->s_blocksize_bits = PAGE_CACHE_SHIFT; sb->s_magic = TMPFS_MAGIC; sb->s_op = &shmem_ops; + sb->s_time_gran = 1; inode = shmem_get_inode(sb, S_IFDIR | mode, 0); if (!inode)