What is negative lookup in linux filesystem

[Praveen Kumar]

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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