Messages in this thread |  | | Date | Tue, 17 Jan 2023 02:41:37 +0000 | | From | Matthew Wilcox <> | | Subject | Re: [PATCH] dax: use switch statement over chained ifs |
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On Mon, Jan 16, 2023 at 06:11:00PM -0800, Amy Parker wrote: > This patch uses a switch statement for pe_order, which improves > readability and on some platforms may minorly improve performance. It > also, to improve readability, recognizes that `PAGE_SHIFT - PAGE_SHIFT' is > a constant, and uses 0 in its place instead. > > Signed-off-by: Amy Parker <apark0006@student.cerritos.edu>
Hi Amy,
Thanks for the patch! Two problems. First, your mailer seems to have mangled the patch; in my tree these are tab indents, and the patch has arrived with four-space indents, so it can't be applied.
The second problem is that this function should simply not exist. I forget how we ended up with enum page_entry_size, but elsewhere we simply pass 'order' around. So what I'd really like to see is a patch series that eliminates page_entry_size everywhere.
I can outline a way to do that in individual patches if that would be helpful.
> fs/dax.c | 13 ++++++++----- > 1 file changed, 8 insertions(+), 5 deletions(-) > > diff --git a/fs/dax.c b/fs/dax.c > index c48a3a93ab29..e8beed601384 100644 > --- a/fs/dax.c > +++ b/fs/dax.c > @@ -32,13 +32,16 @@ > > static inline unsigned int pe_order(enum page_entry_size pe_size) > { > - if (pe_size == PE_SIZE_PTE) > - return PAGE_SHIFT - PAGE_SHIFT; > - if (pe_size == PE_SIZE_PMD) > + switch (pe_size) { > + case PE_SIZE_PTE: > + return 0; > + case PE_SIZE_PMD: > return PMD_SHIFT - PAGE_SHIFT; > - if (pe_size == PE_SIZE_PUD) > + case PE_SIZE_PUD: > return PUD_SHIFT - PAGE_SHIFT; > - return ~0; > + default: > + return ~0; > + } > } > > /* We choose 4096 entries - same as per-zone page wait tables */ > -- > 2.39.0
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