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Revision af5a30d8cfcfc561336f982b06345d6b815e0bb3 authored by Nick Piggin on 03 June 2010, 12:01:46 UTC, committed by Al Viro on 04 June 2010, 21:16:30 UTC 
fix truncate inode time modification breakage
 
mtime and ctime should be changed only if the file size has actually
changed. Patches changing ext2 and tmpfs from vmtruncate to new truncate
sequence has caused regressions where they always update timestamps.

There is some strange cases in POSIX where truncate(2) must not update
times unless the size has acutally changed, see 6e656be89.

This area is all still rather buggy in different ways in a lot of
filesystems and needs a cleanup and audit (ideally the vfs will provide
a simple attribute or call to direct all filesystems exactly which
attributes to change). But coming up with the best solution will take a
while and is not appropriate for rc anyway.

So fix recent regression for now.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
1 parent 8718d36
Raw File
drop_caches.c 
/*
 * Implement the manual drop-all-pagecache function
 */

#include <linux/kernel.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/writeback.h>
#include <linux/sysctl.h>
#include <linux/gfp.h>

/* A global variable is a bit ugly, but it keeps the code simple */
int sysctl_drop_caches;

static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
	struct inode *inode, *toput_inode = NULL;

	spin_lock(&inode_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
		if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
			continue;
		if (inode->i_mapping->nrpages == 0)
			continue;
		__iget(inode);
		spin_unlock(&inode_lock);
		invalidate_mapping_pages(inode->i_mapping, 0, -1);
		iput(toput_inode);
		toput_inode = inode;
		spin_lock(&inode_lock);
	}
	spin_unlock(&inode_lock);
	iput(toput_inode);
}

static void drop_slab(void)
{
	int nr_objects;

	do {
		nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
	} while (nr_objects > 10);
}

int drop_caches_sysctl_handler(ctl_table *table, int write,
	void __user *buffer, size_t *length, loff_t *ppos)
{
	proc_dointvec_minmax(table, write, buffer, length, ppos);
	if (write) {
		if (sysctl_drop_caches & 1)
			iterate_supers(drop_pagecache_sb, NULL);
		if (sysctl_drop_caches & 2)
			drop_slab();
	}
	return 0;
}
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