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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 54089140002 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: 1e9xw6wk8dzk7tsgtgwhy6yrwu3moszh X-HE-Tag: 1710183088-47167 X-HE-Meta: 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 b8qGGhHT 3bt0Vd9yRnSQ8qB9RFKxVadZJu+PyTACq8cBnR3hX2gOSG5uaIypwsdL86gEawAKfdzUZTKS6XVS0iEYps3KEeg8Or593tDjk/3EHnYdqIU/242cjqyviPy9gZUgU4LxHzloEBfp1/aoVAfGqdrHuJFkT2WD0FvPBztlb8YSXei4r1MYM14koysvJXS0v3ELZ8G/qC20I909htaon0/ujiP0cx9+aDYH9a74E7TEivwUHzUE2ltZhyPJzs0aBgcm6k4y0YEDfjZPHwXCeLk3a+pMriu9DM36QyOI2 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: List-Subscribe: List-Unsubscribe: On 04/03/2024 08:13, Barry Song wrote: > From: Chuanhua Han > > While swapping in a large folio, we need to free swaps related to the whole > folio. To avoid frequently acquiring and releasing swap locks, it is better > to introduce an API for batched free. > > Signed-off-by: Chuanhua Han > Co-developed-by: Barry Song > Signed-off-by: Barry Song > --- > include/linux/swap.h | 6 ++++++ > mm/swapfile.c | 35 +++++++++++++++++++++++++++++++++++ > 2 files changed, 41 insertions(+) > > diff --git a/include/linux/swap.h b/include/linux/swap.h > index 2955f7a78d8d..d6ab27929458 100644 > --- a/include/linux/swap.h > +++ b/include/linux/swap.h > @@ -481,6 +481,7 @@ extern void swap_shmem_alloc(swp_entry_t); > extern int swap_duplicate(swp_entry_t); > extern int swapcache_prepare(swp_entry_t); > extern void swap_free(swp_entry_t); > +extern void swap_nr_free(swp_entry_t entry, int nr_pages); nit: In my swap-out v4 series, I've created a batched version of free_swap_and_cache() and called it free_swap_and_cache_nr(). Perhaps it is preferable to align the naming schemes - i.e. call this swap_free_nr(). Your scheme doesn't really work when applied to free_swap_and_cache(). > extern void swapcache_free_entries(swp_entry_t *entries, int n); > extern int free_swap_and_cache(swp_entry_t); > int swap_type_of(dev_t device, sector_t offset); > @@ -561,6 +562,11 @@ static inline void swap_free(swp_entry_t swp) > { > } > > +void swap_nr_free(swp_entry_t entry, int nr_pages) > +{ > + > +} > + > static inline void put_swap_folio(struct folio *folio, swp_entry_t swp) > { > } > diff --git a/mm/swapfile.c b/mm/swapfile.c > index 3f594be83b58..244106998a69 100644 > --- a/mm/swapfile.c > +++ b/mm/swapfile.c > @@ -1341,6 +1341,41 @@ void swap_free(swp_entry_t entry) > __swap_entry_free(p, entry); > } > > +/* > + * Called after swapping in a large folio, batched free swap entries > + * for this large folio, entry should be for the first subpage and > + * its offset is aligned with nr_pages > + */ > +void swap_nr_free(swp_entry_t entry, int nr_pages) > +{ > + int i; > + struct swap_cluster_info *ci; > + struct swap_info_struct *p; > + unsigned type = swp_type(entry); nit: checkpatch.py will complain about bare "unsigned", preferring "unsigned int" or at least it did for me when I did something similar in my swap-out patch set. > + unsigned long offset = swp_offset(entry); > + DECLARE_BITMAP(usage, SWAPFILE_CLUSTER) = { 0 }; I don't love this, as it could blow the stack if SWAPFILE_CLUSTER ever increases. But the only other way I can think of is to explicitly loop over fixed size chunks, and that's not much better. > + > + /* all swap entries are within a cluster for mTHP */ > + VM_BUG_ON(offset % SWAPFILE_CLUSTER + nr_pages > SWAPFILE_CLUSTER); > + > + if (nr_pages == 1) { > + swap_free(entry); > + return; > + } > + > + p = _swap_info_get(entry); You need to handle this returning NULL, like swap_free() does. > + > + ci = lock_cluster(p, offset); The existing swap_free() calls lock_cluster_or_swap_info(). So if swap is backed by rotating media, and clusters are not in use, it will lock the whole swap info. But your new version only calls lock_cluster() which won't lock anything if clusters are not in use. So I think this is a locking bug. > + for (i = 0; i < nr_pages; i++) { > + if (__swap_entry_free_locked(p, offset + i, 1)) > + __bitmap_set(usage, i, 1); > + } > + unlock_cluster(ci); > + > + for_each_clear_bit(i, usage, nr_pages) > + free_swap_slot(swp_entry(type, offset + i)); > +} > + > /* > * Called after dropping swapcache to decrease refcnt to swap entries. > */ Thanks, Ryan