diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt
index 057a3c71d524925fe500961ffdd01947d08e5a14..7097fd29fb3d190f6d7fdb02ff549422d6e14907 100644
--- a/Documentation/filesystems/caching/fscache.txt
+++ b/Documentation/filesystems/caching/fscache.txt
@@ -272,6 +272,10 @@ proc files.
pgs=N Number of pages given store req processing time
rxd=N Number of store reqs deleted from tracking tree
olm=N Number of store reqs over store limit
+ VmScan nos=N Number of release reqs against pages with no pending store
+ gon=N Number of release reqs against pages stored by time lock granted
+ bsy=N Number of release reqs ignored due to in-progress store
+ can=N Number of page stores cancelled due to release req
Ops pend=N Number of times async ops added to pending queues
run=N Number of times async ops given CPU time
enq=N Number of times async ops queued for processing
diff --git a/Documentation/filesystems/caching/netfs-api.txt b/Documentation/filesystems/caching/netfs-api.txt
index 2666b1ed5e9e6515cdda71c878f846438167a0b1..1902c57b72ef7e103a07856dd520aef772c1e684 100644
--- a/Documentation/filesystems/caching/netfs-api.txt
+++ b/Documentation/filesystems/caching/netfs-api.txt
@@ -641,7 +641,7 @@ data file must be retired (see the relinquish cookie function below).
Furthermore, note that this does not cancel the asynchronous read or write
operation started by the read/alloc and write functions, so the page
-invalidation and release functions must use:
+invalidation functions must use:
bool fscache_check_page_write(struct fscache_cookie *cookie,
struct page *page);
@@ -654,6 +654,25 @@ to see if a page is being written to the cache, and:
to wait for it to finish if it is.
+When releasepage() is being implemented, a special FS-Cache function exists to
+manage the heuristics of coping with vmscan trying to eject pages, which may
+conflict with the cache trying to write pages to the cache (which may itself
+need to allocate memory):
+
+ bool fscache_maybe_release_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp);
+
+This takes the netfs cookie, and the page and gfp arguments as supplied to
+releasepage(). It will return false if the page cannot be released yet for
+some reason and if it returns true, the page has been uncached and can now be
+released.
+
+To make a page available for release, this function may wait for an outstanding
+storage request to complete, or it may attempt to cancel the storage request -
+in which case the page will not be stored in the cache this time.
+
+
==========================
INDEX AND DATA FILE UPDATE
==========================
diff --git a/fs/9p/cache.c b/fs/9p/cache.c
index 51c94e26a346f1de790e4f3cac3e039d097c5494..bcc5357a906987147269ba9c020ba6ed642a9ec9 100644
--- a/fs/9p/cache.c
+++ b/fs/9p/cache.c
@@ -343,18 +343,7 @@ int __v9fs_fscache_release_page(struct page *page, gfp_t gfp)
BUG_ON(!vcookie->fscache);
- if (PageFsCache(page)) {
- if (fscache_check_page_write(vcookie->fscache, page)) {
- if (!(gfp & __GFP_WAIT))
- return 0;
- fscache_wait_on_page_write(vcookie->fscache, page);
- }
-
- fscache_uncache_page(vcookie->fscache, page);
- ClearPageFsCache(page);
- }
-
- return 1;
+ return fscache_maybe_release_page(vnode->cache, page, gfp);
}
void __v9fs_fscache_invalidate_page(struct page *page)
@@ -368,7 +357,6 @@ void __v9fs_fscache_invalidate_page(struct page *page)
fscache_wait_on_page_write(vcookie->fscache, page);
BUG_ON(!PageLocked(page));
fscache_uncache_page(vcookie->fscache, page);
- ClearPageFsCache(page);
}
}
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 681c2a7b013fc3c06bfa2d0d75d05804eafb8ffb..39b301662f22449e0896e77bf9a964e68bd9a9f0 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -315,7 +315,6 @@ static void afs_invalidatepage(struct page *page, unsigned long offset)
struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
fscache_wait_on_page_write(vnode->cache, page);
fscache_uncache_page(vnode->cache, page);
- ClearPageFsCache(page);
}
#endif
@@ -349,17 +348,9 @@ static int afs_releasepage(struct page *page, gfp_t gfp_flags)
/* deny if page is being written to the cache and the caller hasn't
* elected to wait */
#ifdef CONFIG_AFS_FSCACHE
- if (PageFsCache(page)) {
- if (fscache_check_page_write(vnode->cache, page)) {
- if (!(gfp_flags & __GFP_WAIT)) {
- _leave(" = F [cache busy]");
- return 0;
- }
- fscache_wait_on_page_write(vnode->cache, page);
- }
-
- fscache_uncache_page(vnode->cache, page);
- ClearPageFsCache(page);
+ if (!fscache_maybe_release_page(vnode->cache, page, gfp_flags)) {
+ _leave(" = F [cache busy]");
+ return 0;
}
#endif
diff --git a/fs/fscache/internal.h b/fs/fscache/internal.h
index a0769872b19cc03da608508716862432e1e262bb..e5046519b153bc729647faf85e8cf4c5d66609b7 100644
--- a/fs/fscache/internal.h
+++ b/fs/fscache/internal.h
@@ -180,6 +180,11 @@ extern atomic_t fscache_n_store_pages;
extern atomic_t fscache_n_store_radix_deletes;
extern atomic_t fscache_n_store_pages_over_limit;
+extern atomic_t fscache_n_store_vmscan_not_storing;
+extern atomic_t fscache_n_store_vmscan_gone;
+extern atomic_t fscache_n_store_vmscan_busy;
+extern atomic_t fscache_n_store_vmscan_cancelled;
+
extern atomic_t fscache_n_marks;
extern atomic_t fscache_n_uncaches;
diff --git a/fs/fscache/page.c b/fs/fscache/page.c
index 022a5da8e130a5538caad2887c0431135723a3b6..fc76798bd968f1bf9b9ebe4bb94d0a206d12d914 100644
--- a/fs/fscache/page.c
+++ b/fs/fscache/page.c
@@ -42,6 +42,75 @@ void __fscache_wait_on_page_write(struct fscache_cookie *cookie, struct page *pa
}
EXPORT_SYMBOL(__fscache_wait_on_page_write);
+/*
+ * decide whether a page can be released, possibly by cancelling a store to it
+ * - we're allowed to sleep if __GFP_WAIT is flagged
+ */
+bool __fscache_maybe_release_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp)
+{
+ struct page *xpage;
+ void *val;
+
+ _enter("%p,%p,%x", cookie, page, gfp);
+
+ rcu_read_lock();
+ val = radix_tree_lookup(&cookie->stores, page->index);
+ if (!val) {
+ rcu_read_unlock();
+ fscache_stat(&fscache_n_store_vmscan_not_storing);
+ __fscache_uncache_page(cookie, page);
+ return true;
+ }
+
+ /* see if the page is actually undergoing storage - if so we can't get
+ * rid of it till the cache has finished with it */
+ if (radix_tree_tag_get(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG)) {
+ rcu_read_unlock();
+ goto page_busy;
+ }
+
+ /* the page is pending storage, so we attempt to cancel the store and
+ * discard the store request so that the page can be reclaimed */
+ spin_lock(&cookie->stores_lock);
+ rcu_read_unlock();
+
+ if (radix_tree_tag_get(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG)) {
+ /* the page started to undergo storage whilst we were looking,
+ * so now we can only wait or return */
+ spin_unlock(&cookie->stores_lock);
+ goto page_busy;
+ }
+
+ xpage = radix_tree_delete(&cookie->stores, page->index);
+ spin_unlock(&cookie->stores_lock);
+
+ if (xpage) {
+ fscache_stat(&fscache_n_store_vmscan_cancelled);
+ fscache_stat(&fscache_n_store_radix_deletes);
+ ASSERTCMP(xpage, ==, page);
+ } else {
+ fscache_stat(&fscache_n_store_vmscan_gone);
+ }
+
+ wake_up_bit(&cookie->flags, 0);
+ if (xpage)
+ page_cache_release(xpage);
+ __fscache_uncache_page(cookie, page);
+ return true;
+
+page_busy:
+ /* we might want to wait here, but that could deadlock the allocator as
+ * the slow-work threads writing to the cache may all end up sleeping
+ * on memory allocation */
+ fscache_stat(&fscache_n_store_vmscan_busy);
+ return false;
+}
+EXPORT_SYMBOL(__fscache_maybe_release_page);
+
/*
* note that a page has finished being written to the cache
*/
@@ -57,6 +126,8 @@ static void fscache_end_page_write(struct fscache_object *object,
/* delete the page from the tree if it is now no longer
* pending */
spin_lock(&cookie->stores_lock);
+ radix_tree_tag_clear(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG);
if (!radix_tree_tag_get(&cookie->stores, page->index,
FSCACHE_COOKIE_PENDING_TAG)) {
fscache_stat(&fscache_n_store_radix_deletes);
@@ -640,8 +711,12 @@ static void fscache_write_op(struct fscache_operation *_op)
goto superseded;
}
- radix_tree_tag_clear(&cookie->stores, page->index,
- FSCACHE_COOKIE_PENDING_TAG);
+ if (page) {
+ radix_tree_tag_set(&cookie->stores, page->index,
+ FSCACHE_COOKIE_STORING_TAG);
+ radix_tree_tag_clear(&cookie->stores, page->index,
+ FSCACHE_COOKIE_PENDING_TAG);
+ }
spin_unlock(&cookie->stores_lock);
spin_unlock(&object->lock);
diff --git a/fs/fscache/stats.c b/fs/fscache/stats.c
index 045ba396dbf23b4da43b797acbb98e2a0c72c330..cda69994e06dbcfb743ce47a98cc103a7441cd9e 100644
--- a/fs/fscache/stats.c
+++ b/fs/fscache/stats.c
@@ -63,6 +63,11 @@ atomic_t fscache_n_store_pages;
atomic_t fscache_n_store_radix_deletes;
atomic_t fscache_n_store_pages_over_limit;
+atomic_t fscache_n_store_vmscan_not_storing;
+atomic_t fscache_n_store_vmscan_gone;
+atomic_t fscache_n_store_vmscan_busy;
+atomic_t fscache_n_store_vmscan_cancelled;
+
atomic_t fscache_n_marks;
atomic_t fscache_n_uncaches;
@@ -211,6 +216,12 @@ static int fscache_stats_show(struct seq_file *m, void *v)
atomic_read(&fscache_n_store_radix_deletes),
atomic_read(&fscache_n_store_pages_over_limit));
+ seq_printf(m, "VmScan : nos=%u gon=%u bsy=%u can=%u\n",
+ atomic_read(&fscache_n_store_vmscan_not_storing),
+ atomic_read(&fscache_n_store_vmscan_gone),
+ atomic_read(&fscache_n_store_vmscan_busy),
+ atomic_read(&fscache_n_store_vmscan_cancelled));
+
seq_printf(m, "Ops : pend=%u run=%u enq=%u can=%u rej=%u\n",
atomic_read(&fscache_n_op_pend),
atomic_read(&fscache_n_op_run),
diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 70fad69eb9593a41894102164e26db60eb13fa56..fa588006588dd3403bb9a883eedc79ddc4588655 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -359,17 +359,13 @@ int nfs_fscache_release_page(struct page *page, gfp_t gfp)
BUG_ON(!cookie);
- if (fscache_check_page_write(cookie, page)) {
- if (!(gfp & __GFP_WAIT))
- return 0;
- fscache_wait_on_page_write(cookie, page);
- }
-
if (PageFsCache(page)) {
dfprintk(FSCACHE, "NFS: fscache releasepage (0x%p/0x%p/0x%p)\n",
cookie, page, nfsi);
- fscache_uncache_page(cookie, page);
+ if (!fscache_maybe_release_page(cookie, page, gfp))
+ return 0;
+
nfs_add_fscache_stats(page->mapping->host,
NFSIOS_FSCACHE_PAGES_UNCACHED, 1);
}
diff --git a/include/linux/fscache-cache.h b/include/linux/fscache-cache.h
index f3aa4bdafef6b946290013c62ab10f563f73c0e5..4750d5fb419fde6f2dd55b566be39759f39caa76 100644
--- a/include/linux/fscache-cache.h
+++ b/include/linux/fscache-cache.h
@@ -317,6 +317,7 @@ struct fscache_cookie {
void *netfs_data; /* back pointer to netfs */
struct radix_tree_root stores; /* pages to be stored on this cookie */
#define FSCACHE_COOKIE_PENDING_TAG 0 /* pages tag: pending write to cache */
+#define FSCACHE_COOKIE_STORING_TAG 1 /* pages tag: writing to cache */
unsigned long flags;
#define FSCACHE_COOKIE_LOOKING_UP 0 /* T if non-index cookie being looked up still */
diff --git a/include/linux/fscache.h b/include/linux/fscache.h
index 6d8ee466e0a00a8b3f4e98927a373869dfee9726..595ce49288b7807f0f42c40a6c2dcde9ed354d36 100644
--- a/include/linux/fscache.h
+++ b/include/linux/fscache.h
@@ -202,6 +202,8 @@ extern int __fscache_write_page(struct fscache_cookie *, struct page *, gfp_t);
extern void __fscache_uncache_page(struct fscache_cookie *, struct page *);
extern bool __fscache_check_page_write(struct fscache_cookie *, struct page *);
extern void __fscache_wait_on_page_write(struct fscache_cookie *, struct page *);
+extern bool __fscache_maybe_release_page(struct fscache_cookie *, struct page *,
+ gfp_t);
/**
* fscache_register_netfs - Register a filesystem as desiring caching services
@@ -615,4 +617,29 @@ void fscache_wait_on_page_write(struct fscache_cookie *cookie,
__fscache_wait_on_page_write(cookie, page);
}
+/**
+ * fscache_maybe_release_page - Consider releasing a page, cancelling a store
+ * @cookie: The cookie representing the cache object
+ * @page: The netfs page that is being cached.
+ * @gfp: The gfp flags passed to releasepage()
+ *
+ * Consider releasing a page for the vmscan algorithm, on behalf of the netfs's
+ * releasepage() call. A storage request on the page may cancelled if it is
+ * not currently being processed.
+ *
+ * The function returns true if the page no longer has a storage request on it,
+ * and false if a storage request is left in place. If true is returned, the
+ * page will have been passed to fscache_uncache_page(). If false is returned
+ * the page cannot be freed yet.
+ */
+static inline
+bool fscache_maybe_release_page(struct fscache_cookie *cookie,
+ struct page *page,
+ gfp_t gfp)
+{
+ if (fscache_cookie_valid(cookie) && PageFsCache(page))
+ return __fscache_maybe_release_page(cookie, page, gfp);
+ return false;
+}
+
#endif /* _LINUX_FSCACHE_H */