diff options
| -rw-r--r-- | Documentation/filesystems/caching/fscache.txt | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/caching/netfs-api.txt | 21 | ||||
| -rw-r--r-- | fs/9p/cache.c | 14 | ||||
| -rw-r--r-- | fs/afs/file.c | 15 | ||||
| -rw-r--r-- | fs/fscache/internal.h | 5 | ||||
| -rw-r--r-- | fs/fscache/page.c | 79 | ||||
| -rw-r--r-- | fs/fscache/stats.c | 11 | ||||
| -rw-r--r-- | fs/nfs/fscache.c | 10 | ||||
| -rw-r--r-- | include/linux/fscache-cache.h | 1 | ||||
| -rw-r--r-- | include/linux/fscache.h | 27 |
10 files changed, 152 insertions, 35 deletions
diff --git a/Documentation/filesystems/caching/fscache.txt b/Documentation/filesystems/caching/fscache.txt index 057a3c7..7097fd2 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 2666b1e..1902c57 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 51c94e2..bcc5357 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 681c2a7..39b3016 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 a076987..e504651 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 022a5da..fc76798 100644 --- a/fs/fscache/page.c +++ b/fs/fscache/page.c @@ -43,6 +43,75 @@ 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 */ static void fscache_end_page_write(struct fscache_object *object, @@ -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 045ba39..cda6999 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 70fad69..fa58800 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 f3aa4bd..4750d5f 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 6d8ee46..595ce49 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 */ |