There is a AB-BA deadlock regarding drop_caches sysctl. Here are the code
paths:
drop_pagecache
spin_lock(&inode_lock);
invalidate_mapping_pages
try_to_release_page
ext3_releasepage
journal_try_to_free_buffers
__journal_try_to_free_buffer
spin_lock(&journal->j_list_lock);
journal_commit_transaction
spin_lock(&journal->j_list_lock);
__journal_remove_checkpoint
__journal_refile_buffer
__journal_unfile_buffer
__journal_temp_unlink_buffer
__set_page_dirty_nobuffers
__mark_inode_dirt
spin_lock(&inode_lock);
The patch tries to address the issue - it drops inode_lock before digging into
invalidate_inode_pages. This seems sane as inode hold should not gone from the
list and should not change its place.
Signed-off-by: Denis V. Lunev <[EMAIL PROTECTED]>
--- ./fs/drop_caches.c.marker 2006-09-20 07:42:06.000000000 +0400
+++ ./fs/drop_caches.c 2007-12-03 15:43:44.000000000 +0300
@@ -14,15 +14,27 @@ int sysctl_drop_caches;
static void drop_pagecache_sb(struct super_block *sb)
{
- struct inode *inode;
+ struct inode *inode, *old;
+ old = NULL;
spin_lock(&inode_lock);
list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
if (inode->i_state & (I_FREEING|I_WILL_FREE))
continue;
+ __iget(inode);
+ spin_unlock(&inode_lock);
+
invalidate_inode_pages(inode->i_mapping);
+ if (old != NULL)
+ iput(old);
+ old = inode;
+
+ spin_lock(&inode_lock);
}
spin_unlock(&inode_lock);
+
+ if (old != NULL)
+ iput(old);
}
void drop_pagecache(void)
--
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