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
