diff options
Diffstat (limited to 'mm/page_io.c')
| -rw-r--r-- | mm/page_io.c | 170 |
1 files changed, 149 insertions, 21 deletions
diff --git a/mm/page_io.c b/mm/page_io.c index ae2b49055e43..f7716b6569fa 100644 --- a/mm/page_io.c +++ b/mm/page_io.c @@ -163,7 +163,6 @@ reprobe: page_no = 1; /* force Empty message */ sis->max = page_no; sis->pages = page_no - 1; - sis->highest_bit = page_no - 1; out: return ret; bad_bmap: @@ -172,13 +171,74 @@ bad_bmap: goto out; } +static bool is_folio_zero_filled(struct folio *folio) +{ + unsigned int pos, last_pos; + unsigned long *data; + unsigned int i; + + last_pos = PAGE_SIZE / sizeof(*data) - 1; + for (i = 0; i < folio_nr_pages(folio); i++) { + data = kmap_local_folio(folio, i * PAGE_SIZE); + /* + * Check last word first, incase the page is zero-filled at + * the start and has non-zero data at the end, which is common + * in real-world workloads. + */ + if (data[last_pos]) { + kunmap_local(data); + return false; + } + for (pos = 0; pos < last_pos; pos++) { + if (data[pos]) { + kunmap_local(data); + return false; + } + } + kunmap_local(data); + } + + return true; +} + +static void swap_zeromap_folio_set(struct folio *folio) +{ + struct obj_cgroup *objcg = get_obj_cgroup_from_folio(folio); + struct swap_info_struct *sis = swp_swap_info(folio->swap); + int nr_pages = folio_nr_pages(folio); + swp_entry_t entry; + unsigned int i; + + for (i = 0; i < folio_nr_pages(folio); i++) { + entry = page_swap_entry(folio_page(folio, i)); + set_bit(swp_offset(entry), sis->zeromap); + } + + count_vm_events(SWPOUT_ZERO, nr_pages); + if (objcg) { + count_objcg_events(objcg, SWPOUT_ZERO, nr_pages); + obj_cgroup_put(objcg); + } +} + +static void swap_zeromap_folio_clear(struct folio *folio) +{ + struct swap_info_struct *sis = swp_swap_info(folio->swap); + swp_entry_t entry; + unsigned int i; + + for (i = 0; i < folio_nr_pages(folio); i++) { + entry = page_swap_entry(folio_page(folio, i)); + clear_bit(swp_offset(entry), sis->zeromap); + } +} + /* * We may have stale swap cache pages in memory: notice * them here and get rid of the unnecessary final write. */ -int swap_writepage(struct page *page, struct writeback_control *wbc) +int swap_writeout(struct folio *folio, struct writeback_control *wbc) { - struct folio *folio = page_folio(page); int ret; if (folio_free_swap(folio)) { @@ -189,16 +249,34 @@ int swap_writepage(struct page *page, struct writeback_control *wbc) * Arch code may have to preserve more data than just the page * contents, e.g. memory tags. */ - ret = arch_prepare_to_swap(&folio->page); + ret = arch_prepare_to_swap(folio); if (ret) { folio_mark_dirty(folio); folio_unlock(folio); return ret; } + + /* + * Use a bitmap (zeromap) to avoid doing IO for zero-filled pages. + * The bits in zeromap are protected by the locked swapcache folio + * and atomic updates are used to protect against read-modify-write + * corruption due to other zero swap entries seeing concurrent updates. + */ + if (is_folio_zero_filled(folio)) { + swap_zeromap_folio_set(folio); + folio_unlock(folio); + return 0; + } else { + /* + * Clear bits this folio occupies in the zeromap to prevent + * zero data being read in from any previous zero writes that + * occupied the same swap entries. + */ + swap_zeromap_folio_clear(folio); + } if (zswap_store(folio)) { - folio_start_writeback(folio); + count_mthp_stat(folio_order(folio), MTHP_STAT_ZSWPOUT); folio_unlock(folio); - folio_end_writeback(folio); return 0; } if (!mem_cgroup_zswap_writeback_enabled(folio_memcg(folio))) { @@ -218,6 +296,8 @@ static inline void count_swpout_vm_event(struct folio *folio) count_vm_event(THP_SWPOUT); } #endif + count_mthp_stat(folio_order(folio), MTHP_STAT_SWPOUT); + count_memcg_folio_events(folio, PSWPOUT, folio_nr_pages(folio)); count_vm_events(PSWPOUT, folio_nr_pages(folio)); } @@ -274,12 +354,10 @@ static void sio_write_complete(struct kiocb *iocb, long ret) * memory for allocating transmit buffers. * Mark the page dirty and avoid * folio_rotate_reclaimable but rate-limit the - * messages but do not flag PageError like - * the normal direct-to-bio case as it could - * be temporary. + * messages. */ pr_err_ratelimited("Write error %ld on dio swapfile (%llu)\n", - ret, page_file_offset(page)); + ret, swap_dev_pos(page_swap_entry(page))); for (p = 0; p < sio->pages; p++) { page = sio->bvec[p].bv_page; set_page_dirty(page); @@ -298,7 +376,7 @@ static void swap_writepage_fs(struct folio *folio, struct writeback_control *wbc struct swap_iocb *sio = NULL; struct swap_info_struct *sis = swp_swap_info(folio->swap); struct file *swap_file = sis->swap_file; - loff_t pos = folio_file_pos(folio); + loff_t pos = swap_dev_pos(folio->swap); count_swpout_vm_event(folio); folio_start_writeback(folio); @@ -383,7 +461,12 @@ void __swap_writepage(struct folio *folio, struct writeback_control *wbc) */ if (data_race(sis->flags & SWP_FS_OPS)) swap_writepage_fs(folio, wbc); - else if (sis->flags & SWP_SYNCHRONOUS_IO) + /* + * ->flags can be updated non-atomicially (scan_swap_map_slots), + * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race + * is safe. + */ + else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO)) swap_writepage_bdev_sync(folio, wbc, sis); else swap_writepage_bdev_async(folio, wbc, sis); @@ -410,6 +493,8 @@ static void sio_read_complete(struct kiocb *iocb, long ret) for (p = 0; p < sio->pages; p++) { struct folio *folio = page_folio(sio->bvec[p].bv_page); + count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN); + count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio)); folio_mark_uptodate(folio); folio_unlock(folio); } @@ -425,11 +510,41 @@ static void sio_read_complete(struct kiocb *iocb, long ret) mempool_free(sio, sio_pool); } +static bool swap_read_folio_zeromap(struct folio *folio) +{ + int nr_pages = folio_nr_pages(folio); + struct obj_cgroup *objcg; + bool is_zeromap; + + /* + * Swapping in a large folio that is partially in the zeromap is not + * currently handled. Return true without marking the folio uptodate so + * that an IO error is emitted (e.g. do_swap_page() will sigbus). + */ + if (WARN_ON_ONCE(swap_zeromap_batch(folio->swap, nr_pages, + &is_zeromap) != nr_pages)) + return true; + + if (!is_zeromap) + return false; + + objcg = get_obj_cgroup_from_folio(folio); + count_vm_events(SWPIN_ZERO, nr_pages); + if (objcg) { + count_objcg_events(objcg, SWPIN_ZERO, nr_pages); + obj_cgroup_put(objcg); + } + + folio_zero_range(folio, 0, folio_size(folio)); + folio_mark_uptodate(folio); + return true; +} + static void swap_read_folio_fs(struct folio *folio, struct swap_iocb **plug) { struct swap_info_struct *sis = swp_swap_info(folio->swap); struct swap_iocb *sio = NULL; - loff_t pos = folio_file_pos(folio); + loff_t pos = swap_dev_pos(folio->swap); if (plug) sio = *plug; @@ -473,7 +588,9 @@ static void swap_read_folio_bdev_sync(struct folio *folio, * attempt to access it in the page fault retry time check. */ get_task_struct(current); - count_vm_event(PSWPIN); + count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN); + count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio)); + count_vm_events(PSWPIN, folio_nr_pages(folio)); submit_bio_wait(&bio); __end_swap_bio_read(&bio); put_task_struct(current); @@ -488,14 +605,16 @@ static void swap_read_folio_bdev_async(struct folio *folio, bio->bi_iter.bi_sector = swap_folio_sector(folio); bio->bi_end_io = end_swap_bio_read; bio_add_folio_nofail(bio, folio, folio_size(folio), 0); - count_vm_event(PSWPIN); + count_mthp_stat(folio_order(folio), MTHP_STAT_SWPIN); + count_memcg_folio_events(folio, PSWPIN, folio_nr_pages(folio)); + count_vm_events(PSWPIN, folio_nr_pages(folio)); submit_bio(bio); } -void swap_read_folio(struct folio *folio, bool synchronous, - struct swap_iocb **plug) +void swap_read_folio(struct folio *folio, struct swap_iocb **plug) { struct swap_info_struct *sis = swp_swap_info(folio->swap); + bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO; bool workingset = folio_test_workingset(folio); unsigned long pflags; bool in_thrashing; @@ -515,17 +634,26 @@ void swap_read_folio(struct folio *folio, bool synchronous, } delayacct_swapin_start(); - if (zswap_load(folio)) { - folio_mark_uptodate(folio); + if (swap_read_folio_zeromap(folio)) { folio_unlock(folio); - } else if (data_race(sis->flags & SWP_FS_OPS)) { + goto finish; + } + + if (zswap_load(folio) != -ENOENT) + goto finish; + + /* We have to read from slower devices. Increase zswap protection. */ + zswap_folio_swapin(folio); + + if (data_race(sis->flags & SWP_FS_OPS)) { swap_read_folio_fs(folio, plug); - } else if (synchronous || (sis->flags & SWP_SYNCHRONOUS_IO)) { + } else if (synchronous) { swap_read_folio_bdev_sync(folio, sis); } else { swap_read_folio_bdev_async(folio, sis); } +finish: if (workingset) { delayacct_thrashing_end(&in_thrashing); psi_memstall_leave(&pflags); |