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SubjectRe: [RFC PATCH 0/2] Fix up the NFS mmap code


On Sat, 9 Jan 2010, Al Viro wrote:
>
> Well, sure - it steps on i_mutex-before-mmmap_sem first from ls somewhere and
> records the ordering for posterity. Then NFS steps into mmap() (on a
> different inode) and gets conflicting ordering.

Look closer: the inodes for directories and for non-directories have
i_mutex in different lockdep classes.

So that "on a different inode" thing should have made it a non-issue,
since there is no actual chain back. There is "mmap_sem ->
i_mutex_regular_file" (for mmap) and there is "i_mutex_directory ->
mmap_sem" (for filldir), but that isn't an ABBA.
The problem _seems_ to be (if I read Andi's chain correctly) that a
directory hasn't gone through the i_mutex_dir_key change, so filldir ends
up being counted against the default i_mutex_key.


Linus


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