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    SubjectRe: [PULL REQUEST] ext3, jbd, ext2, and quota fixes for 3.1-rc1
    On Tue 26-07-11 19:52:20, Al Viro wrote:
    > On Tue, Jul 26, 2011 at 11:36:29AM -0700, Linus Torvalds wrote:
    >
    > > So I *really* want people to take a look at that ext3_sync_file()
    > > function. Please?
    >
    > While we are at it, could somebody please explain what the hell is ext4
    > doing in
    > static int ext4_sync_parent(struct inode *inode)
    > {
    > struct writeback_control wbc;
    > struct dentry *dentry = NULL;
    > int ret = 0;
    >
    > while (inode && ext4_test_inode_state(inode, EXT4_STATE_NEWENTRY)) {
    > ext4_clear_inode_state(inode, EXT4_STATE_NEWENTRY);
    > dentry = list_entry(inode->i_dentry.next,
    > struct dentry, d_alias);
    > if (!dentry || !dentry->d_parent || !dentry->d_parent->d_inode)
    > break;
    > inode = dentry->d_parent->d_inode;
    > ret = sync_mapping_buffers(inode->i_mapping);
    > ...
    > Note that dentry obviously can't be NULL there. dentry->d_parent is never
    > NULL. And dentry->d_parent would better not be negative, for crying out
    > loud! What's worse, there's no guarantees that dentry->d_parent will
    > remain our parent over that sync_mapping_buffers() *and* that inode won't
    > just be freed under us (after rename() and memory pressure leading to
    > eviction of what used to be our dentry->d_parent). Moreover, even if
    > inode survives in icache, there is no promise that it will have an alias
    > in dcache by the time we get to the next iteration of the loop, so this
    > list_entry() next time around can bloody well happen to &inode->i_dentry,
    > dentry being a garbage address somewhere inside that struct inode (or a
    > bit above it - I hadn't compared offsets).
    >
    > What the hell is going on there? It appeared more than a year ago in commit
    > 14ece1028b3ed53ffec1b1213ffc6acaf79ad77c
    > Author: Frank Mayhar <fmayhar@google.com>
    > Date: Mon May 17 08:00:00 2010 -0400
    > ext4: Make fsync sync new parent directories in no-journal mode
    >
    > and it had remained broken ever after...
    It really looks broken. Added Ted to CC...

    Honza
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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