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author | Konstantin Khlebnikov <khlebnikov@openvz.org> | 2012-03-29 01:42:54 +0400 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2012-03-29 04:14:37 +0400 |
commit | 0fc9d1040313047edf6a39fd4d7c7defdca97c62 (patch) | |
tree | 4503c084da1097e1cf66d8bac1ec548bc69ce69a /mm/filemap.c | |
parent | cebbd29e1c2f7a969919f19f74583070840163d7 (diff) | |
download | linux-0fc9d1040313047edf6a39fd4d7c7defdca97c62.tar.xz |
radix-tree: use iterators in find_get_pages* functions
Replace radix_tree_gang_lookup_slot() and
radix_tree_gang_lookup_tag_slot() in page-cache lookup functions with
brand-new radix-tree direct iterating. This avoids the double-scanning
and pointer copying.
Iterator don't stop after nr_pages page-get fails in a row, it continue
lookup till the radix-tree end. Thus we can safely remove these restart
conditions.
Unfortunately, old implementation didn't forbid nr_pages == 0, this corner
case does not fit into new code, so the patch adds an extra check at the
beginning.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.c')
-rw-r--r-- | mm/filemap.c | 86 |
1 files changed, 38 insertions, 48 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index c3811bc6b9e3..79c4b2b0b14e 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -813,20 +813,19 @@ EXPORT_SYMBOL(find_or_create_page); unsigned find_get_pages(struct address_space *mapping, pgoff_t start, unsigned int nr_pages, struct page **pages) { - unsigned int i; - unsigned int ret; - unsigned int nr_found, nr_skip; + struct radix_tree_iter iter; + void **slot; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; rcu_read_lock(); restart: - nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, - (void ***)pages, NULL, start, nr_pages); - ret = 0; - nr_skip = 0; - for (i = 0; i < nr_found; i++) { + radix_tree_for_each_slot(slot, &mapping->page_tree, &iter, start) { struct page *page; repeat: - page = radix_tree_deref_slot((void **)pages[i]); + page = radix_tree_deref_slot(slot); if (unlikely(!page)) continue; @@ -837,7 +836,7 @@ repeat: * when entry at index 0 moves out of or back * to root: none yet gotten, safe to restart. */ - WARN_ON(start | i); + WARN_ON(iter.index); goto restart; } /* @@ -845,7 +844,6 @@ repeat: * here as an exceptional entry: so skip over it - * we only reach this from invalidate_mapping_pages(). */ - nr_skip++; continue; } @@ -853,21 +851,16 @@ repeat: goto repeat; /* Has the page moved? */ - if (unlikely(page != *((void **)pages[i]))) { + if (unlikely(page != *slot)) { page_cache_release(page); goto repeat; } pages[ret] = page; - ret++; + if (++ret == nr_pages) + break; } - /* - * If all entries were removed before we could secure them, - * try again, because callers stop trying once 0 is returned. - */ - if (unlikely(!ret && nr_found > nr_skip)) - goto restart; rcu_read_unlock(); return ret; } @@ -887,21 +880,22 @@ repeat: unsigned find_get_pages_contig(struct address_space *mapping, pgoff_t index, unsigned int nr_pages, struct page **pages) { - unsigned int i; - unsigned int ret; - unsigned int nr_found; + struct radix_tree_iter iter; + void **slot; + unsigned int ret = 0; + + if (unlikely(!nr_pages)) + return 0; rcu_read_lock(); restart: - nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree, - (void ***)pages, NULL, index, nr_pages); - ret = 0; - for (i = 0; i < nr_found; i++) { + radix_tree_for_each_contig(slot, &mapping->page_tree, &iter, index) { struct page *page; repeat: - page = radix_tree_deref_slot((void **)pages[i]); + page = radix_tree_deref_slot(slot); + /* The hole, there no reason to continue */ if (unlikely(!page)) - continue; + break; if (radix_tree_exception(page)) { if (radix_tree_deref_retry(page)) { @@ -924,7 +918,7 @@ repeat: goto repeat; /* Has the page moved? */ - if (unlikely(page != *((void **)pages[i]))) { + if (unlikely(page != *slot)) { page_cache_release(page); goto repeat; } @@ -934,14 +928,14 @@ repeat: * otherwise we can get both false positives and false * negatives, which is just confusing to the caller. */ - if (page->mapping == NULL || page->index != index) { + if (page->mapping == NULL || page->index != iter.index) { page_cache_release(page); break; } pages[ret] = page; - ret++; - index++; + if (++ret == nr_pages) + break; } rcu_read_unlock(); return ret; @@ -962,19 +956,20 @@ EXPORT_SYMBOL(find_get_pages_contig); unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index, int tag, unsigned int nr_pages, struct page **pages) { - unsigned int i; - unsigned int ret; - unsigned int nr_found; + struct radix_tree_iter iter; + void **slot; + unsigned ret = 0; + + if (unlikely(!nr_pages)) + return 0; rcu_read_lock(); restart: - nr_found = radix_tree_gang_lookup_tag_slot(&mapping->page_tree, - (void ***)pages, *index, nr_pages, tag); - ret = 0; - for (i = 0; i < nr_found; i++) { + radix_tree_for_each_tagged(slot, &mapping->page_tree, + &iter, *index, tag) { struct page *page; repeat: - page = radix_tree_deref_slot((void **)pages[i]); + page = radix_tree_deref_slot(slot); if (unlikely(!page)) continue; @@ -998,21 +993,16 @@ repeat: goto repeat; /* Has the page moved? */ - if (unlikely(page != *((void **)pages[i]))) { + if (unlikely(page != *slot)) { page_cache_release(page); goto repeat; } pages[ret] = page; - ret++; + if (++ret == nr_pages) + break; } - /* - * If all entries were removed before we could secure them, - * try again, because callers stop trying once 0 is returned. - */ - if (unlikely(!ret && nr_found)) - goto restart; rcu_read_unlock(); if (ret) |