Messages in this thread | | | From | Yosry Ahmed <> | Date | Mon, 22 May 2023 18:51:10 -0700 | Subject | Re: [PATCH -V2 1/5] swap: Remove get/put_swap_device() in __swap_count() |
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On Mon, May 22, 2023 at 6:48 PM Huang, Ying <ying.huang@intel.com> wrote: > > Yosry Ahmed <yosryahmed@google.com> writes: > > > On Mon, May 22, 2023 at 12:09 AM Huang Ying <ying.huang@intel.com> wrote: > >> > >> __swap_count() is called in do_swap_page() only, which encloses the > >> call site with get/put_swap_device() already. > >> > >> Signed-off-by: "Huang, Ying" <ying.huang@intel.com> > >> Cc: David Hildenbrand <david@redhat.com> > >> Cc: Hugh Dickins <hughd@google.com> > >> Cc: Johannes Weiner <hannes@cmpxchg.org> > >> Cc: Matthew Wilcox <willy@infradead.org> > >> Cc: Michal Hocko <mhocko@suse.com> > >> Cc: Minchan Kim <minchan@kernel.org> > >> Cc: Tim Chen <tim.c.chen@linux.intel.com> > >> Cc: Yang Shi <shy828301@gmail.com> > >> Cc: Yu Zhao <yuzhao@google.com> > >> --- > >> mm/swapfile.c | 10 ++-------- > >> 1 file changed, 2 insertions(+), 8 deletions(-) > >> > >> diff --git a/mm/swapfile.c b/mm/swapfile.c > >> index 274bbf797480..8419cba9c192 100644 > >> --- a/mm/swapfile.c > >> +++ b/mm/swapfile.c > >> @@ -1432,16 +1432,10 @@ void swapcache_free_entries(swp_entry_t *entries, int n) > >> > > > > nit: I would add a comment here that the caller needs get/put_swap_device(). > > It's default behavior to call get/put_swap_device() in the caller for > all almost all swap functions. I would rather comment the swap > functions needn't to do that, as the comments for > read_swap_cache_async() in [2/5].
Fair enough. The comment that you added above get_swap_device() states that all swap-related functions should have some sort of protection against swapoff, so I guess that's sufficient.
My concern is that sometimes people don't know where to look, and having a comment above the function might be helpful. I do agree though that having a comment above ~all swap-related functions pointing to the comment above get_swap_device() is too much.
> > > Reviewed-by: Yosry Ahmed <yosryahmed@google.com> > > Thanks! > > >> int __swap_count(swp_entry_t entry) > >> { > >> - struct swap_info_struct *si; > >> + struct swap_info_struct *si = swp_swap_info(entry); > >> pgoff_t offset = swp_offset(entry); > >> - int count = 0; > >> > >> - si = get_swap_device(entry); > >> - if (si) { > >> - count = swap_count(si->swap_map[offset]); > >> - put_swap_device(si); > >> - } > >> - return count; > >> + return swap_count(si->swap_map[offset]); > >> } > >> > >> /* > > Best Regards, > Huang, Ying
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