The patch titled swap_info: note SWAP_MAP_SHMEM has been added to the -mm tree. Its filename is swap_info-note-swap_map_shmem.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: swap_info: note SWAP_MAP_SHMEM From: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx> While we're fiddling with the swap_map values, let's assign a particular value to shmem/tmpfs swap pages: their swap counts are never incremented, and it helps swapoff's try_to_unuse() a little if it can immediately distinguish those pages from process pages. Since we've no use for SWAP_MAP_BAD | COUNT_CONTINUED, we might as well use that 0xbf value for SWAP_MAP_SHMEM. Signed-off-by: Hugh Dickins <hugh.dickins@xxxxxxxxxxxxx> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- diff -puN include/linux/swap.h~swap_info-note-swap_map_shmem include/linux/swap.h --- a/include/linux/swap.h~swap_info-note-swap_map_shmem +++ a/include/linux/swap.h @@ -157,6 +157,7 @@ enum { #define SWAP_HAS_CACHE 0x40 /* Flag page is cached, in first swap_map */ #define SWAP_CONT_MAX 0x7f /* Max count, in each swap_map continuation */ #define COUNT_CONTINUED 0x80 /* See swap_map continuation for full count */ +#define SWAP_MAP_SHMEM 0xbf /* Owned by shmem/tmpfs, in first swap_map */ /* * The in-memory structure used to track swap areas. @@ -316,6 +317,7 @@ extern swp_entry_t get_swap_page(void); extern swp_entry_t get_swap_page_of_type(int); extern int valid_swaphandles(swp_entry_t, unsigned long *); extern int add_swap_count_continuation(swp_entry_t, gfp_t); +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); @@ -394,6 +396,10 @@ static inline int add_swap_count_continu return 0; } +static inline void swap_shmem_alloc(swp_entry_t swp) +{ +} + static inline int swap_duplicate(swp_entry_t swp) { return 0; diff -puN mm/shmem.c~swap_info-note-swap_map_shmem mm/shmem.c --- a/mm/shmem.c~swap_info-note-swap_map_shmem +++ a/mm/shmem.c @@ -1017,7 +1017,14 @@ int shmem_unuse(swp_entry_t entry, struc goto out; } mutex_unlock(&shmem_swaplist_mutex); -out: return found; /* 0 or 1 or -ENOMEM */ + /* + * Can some race bring us here? We've been holding page lock, + * so I think not; but would rather try again later than BUG() + */ + unlock_page(page); + page_cache_release(page); +out: + return (found < 0) ? found : 0; } /* @@ -1080,7 +1087,7 @@ static int shmem_writepage(struct page * else inode = NULL; spin_unlock(&info->lock); - swap_duplicate(swap); + swap_shmem_alloc(swap); BUG_ON(page_mapped(page)); page_cache_release(page); /* pagecache ref */ swap_writepage(page, wbc); diff -puN mm/swapfile.c~swap_info-note-swap_map_shmem mm/swapfile.c --- a/mm/swapfile.c~swap_info-note-swap_map_shmem +++ a/mm/swapfile.c @@ -548,6 +548,12 @@ static unsigned char swap_entry_free(str if (usage == SWAP_HAS_CACHE) { VM_BUG_ON(!has_cache); has_cache = 0; + } else if (count == SWAP_MAP_SHMEM) { + /* + * Or we could insist on shmem.c using a special + * swap_shmem_free() and free_shmem_swap_and_cache()... + */ + count = 0; } else if ((count & ~COUNT_CONTINUED) <= SWAP_MAP_MAX) { if (count == COUNT_CONTINUED) { if (swap_count_continued(p, offset, count)) @@ -1031,7 +1037,6 @@ static int try_to_unuse(unsigned int typ swp_entry_t entry; unsigned int i = 0; int retval = 0; - int shmem; /* * When searching mms for an entry, a good strategy is to @@ -1107,17 +1112,18 @@ static int try_to_unuse(unsigned int typ /* * Remove all references to entry. - * Whenever we reach init_mm, there's no address space - * to search, but use it as a reminder to search shmem. */ - shmem = 0; swcount = *swap_map; - if (swap_count(swcount)) { - if (start_mm == &init_mm) - shmem = shmem_unuse(entry, page); - else - retval = unuse_mm(start_mm, entry, page); + if (swap_count(swcount) == SWAP_MAP_SHMEM) { + retval = shmem_unuse(entry, page); + /* page has already been unlocked and released */ + if (retval < 0) + break; + continue; } + if (swap_count(swcount) && start_mm != &init_mm) + retval = unuse_mm(start_mm, entry, page); + if (swap_count(*swap_map)) { int set_start_mm = (*swap_map >= swcount); struct list_head *p = &start_mm->mmlist; @@ -1128,7 +1134,7 @@ static int try_to_unuse(unsigned int typ atomic_inc(&new_start_mm->mm_users); atomic_inc(&prev_mm->mm_users); spin_lock(&mmlist_lock); - while (swap_count(*swap_map) && !retval && !shmem && + while (swap_count(*swap_map) && !retval && (p = p->next) != &start_mm->mmlist) { mm = list_entry(p, struct mm_struct, mmlist); if (!atomic_inc_not_zero(&mm->mm_users)) @@ -1142,10 +1148,9 @@ static int try_to_unuse(unsigned int typ swcount = *swap_map; if (!swap_count(swcount)) /* any usage ? */ ; - else if (mm == &init_mm) { + else if (mm == &init_mm) set_start_mm = 1; - shmem = shmem_unuse(entry, page); - } else + else retval = unuse_mm(mm, entry, page); if (set_start_mm && @@ -1162,13 +1167,6 @@ static int try_to_unuse(unsigned int typ mmput(start_mm); start_mm = new_start_mm; } - if (shmem) { - /* page has already been unlocked and released */ - if (shmem > 0) - continue; - retval = shmem; - break; - } if (retval) { unlock_page(page); page_cache_release(page); @@ -2128,6 +2126,15 @@ bad_file: } /* + * Help swapoff by noting that swap entry belongs to shmem/tmpfs + * (in which case its reference count is never incremented). + */ +void swap_shmem_alloc(swp_entry_t entry) +{ + __swap_duplicate(entry, SWAP_MAP_SHMEM); +} + +/* * increase reference count of swap entry by 1. */ int swap_duplicate(swp_entry_t entry) _ Patches currently in -mm which might be from hugh.dickins@xxxxxxxxxxxxx are origin.patch hwpoison-fix-oops-on-ksm-pages.patch hwpoison-fix-proc-meminfo-alignment.patch vmscan-limit-vm_exec-protection-to-file-pages.patch mm-order-evictable-rescue-in-lru-putback.patch mmap-dont-return-enomem-when-mapcount-is-temporarily-exceeded-in-munmap.patch mmap-dont-return-enomem-when-mapcount-is-temporarily-exceeded-in-munmap-checkpatch-fixes.patch vmalloc-adjust-gfp-mask-passed-on-nested-vmalloc-invocation.patch swap_info-private-to-swapfilec.patch swap_info-change-to-array-of-pointers.patch swap_info-include-first_swap_extent.patch swap_info-miscellaneous-minor-cleanups.patch swap_info-swap_has_cache-cleanups.patch swap_info-swap_map-of-chars-not-shorts.patch swap_info-swap-count-continuations.patch swap_info-note-swap_map_shmem.patch swap_info-reorder-its-fields.patch elf-kill-use_elf_core_dump.patch prio_tree-debugging-patch.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html