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authorHugh Dickins <hughd@google.com>2011-07-25 17:12:25 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2011-07-25 20:57:10 -0700
commitb85e0effd3dcbf9118b896232f59526ab1a39a74 (patch)
tree32200b2e4052d50d4eb1771e555eaf66d7c4cfc8 /mm/truncate.c
parent8a549bea51138be2126a2cc6aabe8f17ef66b79b (diff)
mm: consistent truncate and invalidate loops
Make the pagevec_lookup loops in truncate_inode_pages_range(), invalidate_mapping_pages() and invalidate_inode_pages2_range() more consistent with each other. They were relying upon page->index of an unlocked page, but apologizing for it: accept it, embrace it, add comments and WARN_ONs, and simplify the index handling. invalidate_inode_pages2_range() had special handling for a wrapped page->index + 1 = 0 case; but MAX_LFS_FILESIZE doesn't let us anywhere near there, and a corrupt page->index in the radix_tree could cause more trouble than that would catch. Remove that wrapped handling. invalidate_inode_pages2_range() uses min() to limit the pagevec_lookup when near the end of the range: copy that into the other two, although it's less useful than you might think (it limits the use of the buffer, rather than the indices looked up). Signed-off-by: Hugh Dickins <hughd@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/truncate.c')
-rw-r--r--mm/truncate.c110
1 files changed, 47 insertions, 63 deletions
diff --git a/mm/truncate.c b/mm/truncate.c
index c924764e2ce5..dc459014f777 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -199,9 +199,6 @@ int invalidate_inode_page(struct page *page)
* The first pass will remove most pages, so the search cost of the second pass
* is low.
*
- * When looking at page->index outside the page lock we need to be careful to
- * copy it into a local to avoid races (it could change at any time).
- *
* We pass down the cache-hot hint to the page freeing code. Even if the
* mapping is large, it is probably the case that the final pages are the most
* recently touched, and freeing happens in ascending file offset order.
@@ -210,10 +207,10 @@ void truncate_inode_pages_range(struct address_space *mapping,
loff_t lstart, loff_t lend)
{
const pgoff_t start = (lstart + PAGE_CACHE_SIZE-1) >> PAGE_CACHE_SHIFT;
- pgoff_t end;
const unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
struct pagevec pvec;
- pgoff_t next;
+ pgoff_t index;
+ pgoff_t end;
int i;
cleancache_flush_inode(mapping);
@@ -224,24 +221,21 @@ void truncate_inode_pages_range(struct address_space *mapping,
end = (lend >> PAGE_CACHE_SHIFT);
pagevec_init(&pvec, 0);
- next = start;
- while (next <= end &&
- pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
+ index = start;
+ while (index <= end && pagevec_lookup(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- pgoff_t page_index = page->index;
- if (page_index > end) {
- next = page_index;
+ /* We rely upon deletion not changing page->index */
+ index = page->index;
+ if (index > end)
break;
- }
- if (page_index > next)
- next = page_index;
- next++;
if (!trylock_page(page))
continue;
+ WARN_ON(page->index != index);
if (PageWriteback(page)) {
unlock_page(page);
continue;
@@ -252,6 +246,7 @@ void truncate_inode_pages_range(struct address_space *mapping,
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
+ index++;
}
if (partial) {
@@ -264,13 +259,14 @@ void truncate_inode_pages_range(struct address_space *mapping,
}
}
- next = start;
+ index = start;
for ( ; ; ) {
cond_resched();
- if (!pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
- if (next == start)
+ if (!pagevec_lookup(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+ if (index == start)
break;
- next = start;
+ index = start;
continue;
}
if (pvec.pages[0]->index > end) {
@@ -281,18 +277,20 @@ void truncate_inode_pages_range(struct address_space *mapping,
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- if (page->index > end)
+ /* We rely upon deletion not changing page->index */
+ index = page->index;
+ if (index > end)
break;
+
lock_page(page);
+ WARN_ON(page->index != index);
wait_on_page_writeback(page);
truncate_inode_page(mapping, page);
- if (page->index > next)
- next = page->index;
- next++;
unlock_page(page);
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
+ index++;
}
cleancache_flush_inode(mapping);
}
@@ -333,35 +331,26 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
struct pagevec pvec;
- pgoff_t next = start;
+ pgoff_t index = start;
unsigned long ret;
unsigned long count = 0;
int i;
pagevec_init(&pvec, 0);
- while (next <= end &&
- pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) {
+ while (index <= end && pagevec_lookup(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- pgoff_t index;
- int lock_failed;
-
- lock_failed = !trylock_page(page);
- /*
- * We really shouldn't be looking at the ->index of an
- * unlocked page. But we're not allowed to lock these
- * pages. So we rely upon nobody altering the ->index
- * of this (pinned-by-us) page.
- */
+ /* We rely upon deletion not changing page->index */
index = page->index;
- if (index > next)
- next = index;
- next++;
- if (lock_failed)
- continue;
+ if (index > end)
+ break;
+ if (!trylock_page(page))
+ continue;
+ WARN_ON(page->index != index);
ret = invalidate_inode_page(page);
unlock_page(page);
/*
@@ -371,12 +360,11 @@ unsigned long invalidate_mapping_pages(struct address_space *mapping,
if (!ret)
deactivate_page(page);
count += ret;
- if (next > end)
- break;
}
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
+ index++;
}
return count;
}
@@ -442,37 +430,32 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
struct pagevec pvec;
- pgoff_t next;
+ pgoff_t index;
int i;
int ret = 0;
int ret2 = 0;
int did_range_unmap = 0;
- int wrapped = 0;
cleancache_flush_inode(mapping);
pagevec_init(&pvec, 0);
- next = start;
- while (next <= end && !wrapped &&
- pagevec_lookup(&pvec, mapping, next,
- min(end - next, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+ index = start;
+ while (index <= end && pagevec_lookup(&pvec, mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- pgoff_t page_index;
+
+ /* We rely upon deletion not changing page->index */
+ index = page->index;
+ if (index > end)
+ break;
lock_page(page);
+ WARN_ON(page->index != index);
if (page->mapping != mapping) {
unlock_page(page);
continue;
}
- page_index = page->index;
- next = page_index + 1;
- if (next == 0)
- wrapped = 1;
- if (page_index > end) {
- unlock_page(page);
- break;
- }
wait_on_page_writeback(page);
if (page_mapped(page)) {
if (!did_range_unmap) {
@@ -480,9 +463,9 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
* Zap the rest of the file in one hit.
*/
unmap_mapping_range(mapping,
- (loff_t)page_index<<PAGE_CACHE_SHIFT,
- (loff_t)(end - page_index + 1)
- << PAGE_CACHE_SHIFT,
+ (loff_t)index << PAGE_CACHE_SHIFT,
+ (loff_t)(1 + end - index)
+ << PAGE_CACHE_SHIFT,
0);
did_range_unmap = 1;
} else {
@@ -490,8 +473,8 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
* Just zap this page
*/
unmap_mapping_range(mapping,
- (loff_t)page_index<<PAGE_CACHE_SHIFT,
- PAGE_CACHE_SIZE, 0);
+ (loff_t)index << PAGE_CACHE_SHIFT,
+ PAGE_CACHE_SIZE, 0);
}
}
BUG_ON(page_mapped(page));
@@ -507,6 +490,7 @@ int invalidate_inode_pages2_range(struct address_space *mapping,
pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
+ index++;
}
cleancache_flush_inode(mapping);
return ret;

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