linux-kernel - Re: [PATCH v2 11/61] mm: Remove rb tree.

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Message-ID: <20210831143949.wr2aizw5qmpc4fsh@revolver>
Date:   Tue, 31 Aug 2021 14:40:03 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     David Hildenbrand <david@...hat.com>
CC:     "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>
Subject: Re: [PATCH v2 11/61] mm: Remove rb tree.

* David Hildenbrand <david@...hat.com> [210823 05:49]:
> On 17.08.21 17:47, Liam Howlett wrote:
> > From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> > 
> > Remove the RB tree and start using the maple tree for vm_area_struct
> > tracking.
> > 
> > Drop validate_mm() calls in expand_upwards() and expand_downwards() as
> > the lock is not held.
> > 
> > Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>
> 
> 
> [...]
> 
> 
> Why are we reshuffling the code below? This either needs a good
> justification or should just be dropped as it introduces noise. Maybe I am
> missing something important.
> 
> >   	/*
> > @@ -427,6 +414,11 @@ struct vm_area_struct {
> >   	pgprot_t vm_page_prot;
> >   	unsigned long vm_flags;		/* Flags, see mm.h. */
> > +	/* Information about our backing store: */
> > +	unsigned long vm_pgoff;		/* Offset (within vm_file) in PAGE_SIZE
> > +					 * units
> > +					 */
> > +	struct file *vm_file;		/* File we map to (can be NULL). */
> >   	/*
> >   	 * For areas with an address space and backing store,
> >   	 * linkage into the address_space->i_mmap interval tree.
> > @@ -449,12 +441,9 @@ struct vm_area_struct {
> >   	/* Function pointers to deal with this struct. */
> >   	const struct vm_operations_struct *vm_ops;
> > -	/* Information about our backing store: */
> > -	unsigned long vm_pgoff;		/* Offset (within vm_file) in PAGE_SIZE
> > -					   units */
> > -	struct file * vm_file;		/* File we map to (can be NULL). */
> >   	void * vm_private_data;		/* was vm_pte (shared mem) */
> > +

Thank you, I will drop this from the next revision.

> 
> Another unrelated change (there seem to some more in this patch)

I'll have a look though it again.

Thanks,
Liam