[TLDR: I'm adding this regression to regzbot, the Linux kernel regression tracking bot; most text you find below is compiled from a few templates paragraphs some of you might have seen already.] Hi, this is your Linux kernel regression tracker speaking. Adding the regression mailing list to the list of recipients, as it should be in the loop for all regressions, as explained here: https://www.kernel.org/doc/html/latest/admin-guide/reporting-issues.html On 15.01.22 04:11, Ivan Delalande wrote: > Hi, > > Sorry to bring this up so late but we might have found a regression > introduced by your "Sort out fsnotify_nameremove() mess" patch series > merged in 5.3 (116b9731ad76..7377f5bec133), and that can still be > reproduced on v5.16. > > Some of our processes use inotify to watch for IN_DELETE events (for > files on tmpfs mostly), and relied on the fact that once such events are > received, the files they refer to have actually been unlinked and can't > be open/read. So if and once open() succeeds then it is a new version of > the file that has been recreated with new content. > > This was true and working reliably before 5.3, but changed after > 49246466a989 ("fsnotify: move fsnotify_nameremove() hook out of > d_delete()") specifically. There is now a time window where a process > receiving one of those IN_DELETE events may still be able to open the > file and read its old content before it's really unlinked from the FS. > > I'm not very familiar with the VFS and fsnotify internals, would you > consider this a regression, or was there never any intentional guarantee > for that behavior and it's best we work around this change in userspace? Thanks for the report. To be sure this issue doesn't fall through the cracks unnoticed, I'm adding it to regzbot, my Linux kernel regression tracking bot: #regzbot ^introduced 116b9731ad76..7377f5bec133 #regzbot title fsnotify: regression due to the fsnotify_nameremove() rework in 5.3 #regzbot ignore-activity Reminder: when fixing the issue, please add a 'Link:' tag with the URL to the report (the parent of this mail) using the kernel.org redirector, as explained in 'Documentation/process/submitting-patches.rst'. Regzbot then will automatically mark the regression as resolved once the fix lands in the appropriate tree. For more details about regzbot see footer. Sending this to everyone that got the initial report, to make all aware of the tracking. I also hope that messages like this motivate people to directly get at least the regression mailing list and ideally even regzbot involved when dealing with regressions, as messages like this wouldn't be needed then. Don't worry, I'll send further messages wrt to this regression just to the lists (with a tag in the subject so people can filter them away), as long as they are intended just for regzbot. With a bit of luck no such messages will be needed anyway. Ciao, Thorsten (wearing his 'Linux kernel regression tracker' hat) P.S.: As a Linux kernel regression tracker I'm getting a lot of reports on my table. I can only look briefly into most of them. Unfortunately therefore I sometimes will get things wrong or miss something important. I hope that's not the case here; if you think it is, don't hesitate to tell me about it in a public reply, that's in everyone's interest. BTW, I have no personal interest in this issue, which is tracked using regzbot, my Linux kernel regression tracking bot (https://linux-regtracking.leemhuis.info/regzbot/). I'm only posting this mail to get things rolling again and hence don't need to be CC on all further activities wrt to this regression. --- Additional information about regzbot: If you want to know more about regzbot, check out its web-interface, the getting start guide, and/or the references documentation: https://linux-regtracking.leemhuis.info/regzbot/ https://gitlab.com/knurd42/regzbot/-/blob/main/docs/getting_started.md https://gitlab.com/knurd42/regzbot/-/blob/main/docs/reference.md The last two documents will explain how you can interact with regzbot yourself if your want to. Hint for reporters: when reporting a regression it's in your interest to tell #regzbot about it in the report, as that will ensure the regression gets on the radar of regzbot and the regression tracker. That's in your interest, as they will make sure the report won't fall through the cracks unnoticed. Hint for developers: you normally don't need to care about regzbot once it's involved. Fix the issue as you normally would, just remember to include a 'Link:' tag to the report in the commit message, as explained in Documentation/process/submitting-patches.rst That aspect was recently was made more explicit in commit 1f57bd42b77c: https://git.kernel.org/linus/1f57bd42b77c
