ext2: Fix link count corruption under heavy link+rename load (03885ac3) · Commits · 戴 / test

vfs_rename_other() does not lock renamed inode with i_mutex. Thus changing i_nlink in a non-atomic manner (which happens in ext2_rename()) can corrupt it as reported and analyzed by Josh. In fact, there is no good reason to mess with i_nlink of the moved file. We did it presumably to simulate linking into the new directory and unlinking from an old one. But the practical effect of this is disputable because fsck can possibly treat file as being properly linked into both directories without writing any error which is confusing. So we just stop increment-decrement games with i_nlink which also fixes the corruption. CC: stable@kernel.org CC: Al Viro <viro@ZenIV.linux.org.uk> Signed-off-by:

Josh Hunt <johunt@akamai.com> Signed-off-by:

Jan Kara <jack@suse.cz>

fs/ext2/namei.c

+2 −7

Original line number	Diff line number	Diff line
		@@ -344,7 +344,6 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
		new_de = ext2_find_entry (new_dir, &new_dentry->d_name, &new_page);
		if (!new_de)
		goto out_dir;
		inode_inc_link_count(old_inode);
		ext2_set_link(new_dir, new_de, new_page, old_inode, 1);
		new_inode->i_ctime = CURRENT_TIME_SEC;
		if (dir_de)
		@@ -356,12 +355,9 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
		if (new_dir->i_nlink >= EXT2_LINK_MAX)
		goto out_dir;
		}
		inode_inc_link_count(old_inode);
		err = ext2_add_link(new_dentry, old_inode);
		if (err) {
		inode_dec_link_count(old_inode);
		if (err)
		goto out_dir;
		}
		if (dir_de)
		inode_inc_link_count(new_dir);
		}
		@@ -369,12 +365,11 @@ static int ext2_rename (struct inode * old_dir, struct dentry * old_dentry,
		/*
		* Like most other Unix systems, set the ctime for inodes on a
		* rename.
		* inode_dec_link_count() will mark the inode dirty.
		*/
		old_inode->i_ctime = CURRENT_TIME_SEC;
		mark_inode_dirty(old_inode);

		ext2_delete_entry (old_de, old_page);
		inode_dec_link_count(old_inode);

		if (dir_de) {
		if (old_dir != new_dir)

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