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![Wu Fengguang](/assets/img/avatar_default.png)
clear_inode() will switch inode state from I_FREEING to I_CLEAR, and do so _outside_ of inode_lock. So any I_FREEING testing is incomplete without a coupled testing of I_CLEAR. So add I_CLEAR tests to drop_pagecache_sb(), generic_sync_sb_inodes() and add_dquot_ref(). Masayoshi MIZUMA discovered the bug in drop_pagecache_sb() and Jan Kara reminds fixing the other two cases. Masayoshi MIZUMA has a nice panic flow: ===================================================================== [process A] | [process B] | | | prune_icache() | drop_pagecache() | spin_lock(&inode_lock) | drop_pagecache_sb() | inode->i_state |= I_FREEING; | | | spin_unlock(&inode_lock) | V | | | spin_lock(&inode_lock) | V | | | dispose_list() | | | list_del() | | | clear_inode() | | | inode->i_state = I_CLEAR | | | | | V | | | if (inode->i_state & (I_FREEING|I_WILL_FREE)) | | | continue; <==== NOT MATCH | | | | | | (DANGER from here on! Accessing disposing inode!) | | | | | | __iget() | | | list_move() <===== PANIC on poisoned list !! V V | (time) ===================================================================== Reported-by: Masayoshi MIZUMA <m.mizuma@jp.fujitsu.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Wu Fengguang <fengguang.wu@intel.com> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
76 lines
1.7 KiB
C
76 lines
1.7 KiB
C
/*
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* Implement the manual drop-all-pagecache function
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*/
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#include <linux/kernel.h>
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#include <linux/mm.h>
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#include <linux/fs.h>
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#include <linux/writeback.h>
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#include <linux/sysctl.h>
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#include <linux/gfp.h>
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/* A global variable is a bit ugly, but it keeps the code simple */
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int sysctl_drop_caches;
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static void drop_pagecache_sb(struct super_block *sb)
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{
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struct inode *inode, *toput_inode = NULL;
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spin_lock(&inode_lock);
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list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
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if (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
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continue;
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if (inode->i_mapping->nrpages == 0)
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continue;
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__iget(inode);
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spin_unlock(&inode_lock);
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__invalidate_mapping_pages(inode->i_mapping, 0, -1, true);
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iput(toput_inode);
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toput_inode = inode;
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spin_lock(&inode_lock);
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}
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spin_unlock(&inode_lock);
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iput(toput_inode);
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}
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static void drop_pagecache(void)
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{
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struct super_block *sb;
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spin_lock(&sb_lock);
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restart:
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list_for_each_entry(sb, &super_blocks, s_list) {
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sb->s_count++;
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spin_unlock(&sb_lock);
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down_read(&sb->s_umount);
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if (sb->s_root)
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drop_pagecache_sb(sb);
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up_read(&sb->s_umount);
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spin_lock(&sb_lock);
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if (__put_super_and_need_restart(sb))
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goto restart;
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}
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spin_unlock(&sb_lock);
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}
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static void drop_slab(void)
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{
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int nr_objects;
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do {
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nr_objects = shrink_slab(1000, GFP_KERNEL, 1000);
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} while (nr_objects > 10);
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}
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int drop_caches_sysctl_handler(ctl_table *table, int write,
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struct file *file, void __user *buffer, size_t *length, loff_t *ppos)
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{
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proc_dointvec_minmax(table, write, file, buffer, length, ppos);
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if (write) {
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if (sysctl_drop_caches & 1)
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drop_pagecache();
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if (sysctl_drop_caches & 2)
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drop_slab();
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}
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return 0;
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}
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