Messages in this thread |  | | From | Linus Torvalds <> | | Date | Thu, 4 Jan 2024 12:18:06 -0800 | | Subject | Re: [for-next][PATCH 2/3] eventfs: Stop using dcache_readdir() for getdents() |
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On Thu, 4 Jan 2024 at 12:04, Steven Rostedt <rostedt@goodmis.org> wrote: > > Also, I just realized it breaks if we update the 'c--' before the callback. :-/ > > I have to put this check *after* the callback check.
What? No.
> Reason being, the callback can say "this event doesn't get this file" and > return 0, which tells eventfs to skip this file.
So yes, there seems to be a bug there, in that ctx->pos is only updated for successful callbacks (and not for "ignored entry").
But that just means that you should always update 'ctx->pos' as you 'continue' the loop.
The logical place to do that would be in the for-loop itself, which actually is very natural for the simple case, ie you should just do
for (i = 0; i < ei->nr_entries; i++, ctx->pos++) {
but in the list_for_each_entry_srcu() case the 'update' part of the for-loop isn't actually accessible, so it would have to be at the 'continue' point(s).
Which is admittedly a bit annoying.
Looking at that I'm actually surprised that I don't recall that we'd have hit that issue with our 'for_each_xyz()' loops before.
The update for our "for_each_xyz()" helpers are all hardcoded to just do the "next iterator" thing, and there's no nice way to take advantage of the normal for-loop semantics of "do this at the end of the loop"
Linus
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