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Date: Thu, 23 May 2019 16:40:50 +0200 From: Jan Kara <jack@...e.cz> To: Christian Brauner <christian@...uner.io> Cc: Amir Goldstein <amir73il@...il.com>, Jan Kara <jack@...e.cz>, linux-fsdevel <linux-fsdevel@...r.kernel.org>, linux-kernel <linux-kernel@...r.kernel.org>, Matthew Bobrowski <mbobrowski@...browski.org> Subject: Re: [PATCH] fanotify: remove redundant capable(CAP_SYS_ADMIN)s On Thu 23-05-19 15:35:18, Christian Brauner wrote: > So let's say the user tells me: > - When the "/A/B/C/target" file appears on the host filesystem, > please give me access to "target" in the container at a path I tell > you. > What I do right now is listen for the creation of the "target" file. > But at the time the user gives me instructions to listen for > "/A/B/C/target" only /A might exist and so I currently add a watch on A/ > and then wait for the creation of B/, then wait for the creation of C/ > and finally for the creation of "target" (Of course, I also need to > handle B/ and C/ being removed again an recreated and so on.). It would > be helpful, if I could specify, give me notifications, recursively for > e.g. A/ without me having to place extra watches on B/ and C/ when they > appear. Maybe that's out of scope... I see. But this is going to be painful whatever you do. Consider for example situation like: mkdir -p BAR/B/C/ touch BAR/B/C/target mv BAR A Or even situation where several renames race so that the end result creates the name (or does not create it depending on how renames race). And by the time you decide A/B/C/target exists, it doesn't need to exist anymore. Honestly I don't see how you want to implement *any* solution in a sane way. About the most reliable+simple would seem to be stat "A/B/C/target" once per second as dumb as it is. Honza -- Jan Kara <jack@...e.com> SUSE Labs, CR
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