From: Jason Gunthorpe <jgg@ziepe.ca>
To: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox <willy@infradead.org>,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH 8/8] xarray: Don't clear marks in xas_store()
Date: Thu, 6 Feb 2020 10:49:10 -0400 [thread overview]
Message-ID: <20200206144909.GH25297@ziepe.ca> (raw)
In-Reply-To: <20200206143627.GA26114@quack2.suse.cz>
On Thu, Feb 06, 2020 at 03:36:27PM +0100, Jan Kara wrote:
> Yeah, that's why I'd prefer if NULL was not "special value" at all and if
> someone wanted to remove index from xarray he'd always have to use a
> special function. My patches go towards that direction but not the full way
> because there's still xa_cmpxchg() whose users use the fact that NULL is in
> fact 'erase'.
IMHO, this is more appealing. The fact that xa_store(NULL) on
non-allocating arrays changes marks seems very surprising/counter
intuitive. It feels wise to avoid subtle differences like this between
allocating/non-allocating mode.
So, it would be more uniform if xa_store and xa_cmpxchg never altered
marks. I suppose in practice this means that xa_store(NULL) has to
store a XA_ZERO_ENTRY even for non-allocating arrays, and related.
Perhaps xa_cmp_erase() could be introduced to take the place of
cmpxchg(NULL), and the distinction between erase and store NULL is
that erase has the mark-destroying property and guarentees the tree
can be pruned.
Jason
next prev parent reply other threads:[~2020-02-06 14:49 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 14:25 [PATCH 0/8] mm: Speedup page cache truncation Jan Kara
2020-02-04 14:25 ` [PATCH 1/8] xarray: Fix premature termination of xas_for_each_marked() Jan Kara
2020-03-12 21:45 ` Matthew Wilcox
2020-03-16 9:16 ` Jan Kara
2020-02-04 14:25 ` [PATCH 2/8] xarray: Provide xas_erase() helper Jan Kara
2020-03-14 19:54 ` Matthew Wilcox
2020-03-16 9:21 ` Jan Kara
2020-03-17 15:28 ` Matthew Wilcox
2020-04-15 16:12 ` Jan Kara
2020-02-04 14:25 ` [PATCH 3/8] xarray: Explicitely set XA_FREE_MARK in __xa_cmpxchg() Jan Kara
2020-02-05 18:45 ` Jason Gunthorpe
2020-02-06 8:03 ` Jan Kara
2020-03-17 15:12 ` Matthew Wilcox
2020-02-04 14:25 ` [PATCH 4/8] mm: Use xas_erase() in page_cache_delete_batch() Jan Kara
2020-02-04 14:25 ` [PATCH 5/8] dax: Use xas_erase() in __dax_invalidate_entry() Jan Kara
2020-02-04 14:25 ` [PATCH 6/8] idr: Use xas_erase() in ida_destroy() Jan Kara
2020-02-04 14:25 ` [PATCH 7/8] mm: Use xas_erase() in collapse_file() Jan Kara
2020-02-04 14:25 ` [PATCH 8/8] xarray: Don't clear marks in xas_store() Jan Kara
2020-02-05 18:43 ` Jason Gunthorpe
2020-02-05 21:59 ` Matthew Wilcox
2020-02-06 13:49 ` Jason Gunthorpe
2020-02-06 14:36 ` Jan Kara
2020-02-06 14:49 ` Jason Gunthorpe [this message]
2020-02-05 22:19 ` John Hubbard
2020-02-06 2:21 ` Matthew Wilcox
2020-02-06 3:48 ` John Hubbard
2020-02-06 4:28 ` Matthew Wilcox
2020-02-06 4:37 ` John Hubbard
2020-02-06 8:36 ` Jan Kara
2020-02-06 8:04 ` Jan Kara
2020-02-06 14:40 ` [PATCH 0/8] mm: Speedup page cache truncation David Sterba
2020-02-18 9:25 ` Jan Kara
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