From the context of the snippet you posted, it looks like the author implies a "failed lookup" when s/he writes "negative lookup".

CMIIW. -mandeep On Mon, Oct 5, 2015 at 8:08 AM, Praveen Kumar <kpraveen.lkml@gmail.com> wrote:

Hi,

I am trying to understand the path-lookup in linux filesystem and was going through https://www.kernel.org/doc/Documentation/filesystems/path-lookup.txt

Under 'Rename' heading, I came across the negative lookup terminology, snapshot below

'Between deleting the dentry from the old hash list, and inserting it on the new hash list, a lookup may find neither 'A' nor 'B' matching the dentry. The same rename seqlock is also used to cover this race in much the same way, by retrying a negative lookup result if a rename was in progress.'

Can anyone please help understanding the negative lookup concept and how do we achieve it. Thanks in advance.

Regards,

~Praveen.

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