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[79.43.135.105]) by smtp.gmail.com with ESMTPSA id k16sm19719262wrp.66.2020.06.01.09.06.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Jun 2020 09:06:45 -0700 (PDT) From: Andrea Righi To: "Rafael J . Wysocki" , Pavel Machek Cc: Len Brown , Andrew Morton , linux-pm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 1/2] mm: swap: allow partial swapoff with try_to_unuse() Date: Mon, 1 Jun 2020 18:06:35 +0200 Message-Id: <20200601160636.148346-2-andrea.righi@canonical.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200601160636.148346-1-andrea.righi@canonical.com> References: <20200601160636.148346-1-andrea.righi@canonical.com> MIME-Version: 1.0 X-Rspamd-Queue-Id: 5333A1ACC27 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam03 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Allow to run try_to_unuse() passing an arbitrary amount of pages also when frontswap is not used. To preserve the default behavior introduce a new function called try_to_unuse_wait() and add a new 'wait' parameter: if 'wait' is false return as soon as "pages_to_unuse" pages are unused, if it is true simply ignore "pages_to_unuse" and wait until all the pages are unused. In any case the value of 0 in "pages_to_unuse" means "all pages". This is required by the PM / hibernation opportunistic memory reclaim feature. Signed-off-by: Andrea Righi --- include/linux/swapfile.h | 7 +++++++ mm/swapfile.c | 15 +++++++-------- 2 files changed, 14 insertions(+), 8 deletions(-) diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h index e06febf62978..ac4d0ccd1f7b 100644 --- a/include/linux/swapfile.h +++ b/include/linux/swapfile.h @@ -9,6 +9,13 @@ extern spinlock_t swap_lock; extern struct plist_head swap_active_head; extern struct swap_info_struct *swap_info[]; +extern int try_to_unuse_wait(unsigned int type, bool frontswap, bool wait, + unsigned long pages_to_unuse); +static inline int +try_to_unuse(unsigned int type, bool frontswap, unsigned long pages_to_unuse) +{ + return try_to_unuse_wait(type, frontswap, true, pages_to_unuse); +} extern int try_to_unuse(unsigned int, bool, unsigned long); extern unsigned long generic_max_swapfile_size(void); extern unsigned long max_swapfile_size(void); diff --git a/mm/swapfile.c b/mm/swapfile.c index f8bf926c9c8f..651471ccf133 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -2121,10 +2121,13 @@ static unsigned int find_next_to_unuse(struct swap_info_struct *si, } /* - * If the boolean frontswap is true, only unuse pages_to_unuse pages; - * pages_to_unuse==0 means all pages; ignored if frontswap is false + * Unuse pages_to_unuse pages; pages_to_unuse==0 means all pages. + * + * If "wait" is false stop as soon as "pages_to_unuse" pages are unused, if + * wait is true "pages_to_unuse" will be ignored and wait until all the pages + * are unused. */ -int try_to_unuse(unsigned int type, bool frontswap, +int try_to_unuse_wait(unsigned int type, bool frontswap, bool wait, unsigned long pages_to_unuse) { struct mm_struct *prev_mm; @@ -2138,10 +2141,6 @@ int try_to_unuse(unsigned int type, bool frontswap, if (!READ_ONCE(si->inuse_pages)) return 0; - - if (!frontswap) - pages_to_unuse = 0; - retry: retval = shmem_unuse(type, frontswap, &pages_to_unuse); if (retval) @@ -2223,7 +2222,7 @@ int try_to_unuse(unsigned int type, bool frontswap, * been preempted after get_swap_page(), temporarily hiding that swap. * It's easy and robust (though cpu-intensive) just to keep retrying. */ - if (READ_ONCE(si->inuse_pages)) { + if (wait && READ_ONCE(si->inuse_pages)) { if (!signal_pending(current)) goto retry; retval = -EINTR;