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-rw-r--r--mm/shmem.c192
1 files changed, 146 insertions, 46 deletions
diff --git a/mm/shmem.c b/mm/shmem.c
index e101c211ed1f..4439b7d55819 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -238,6 +238,111 @@ static swp_entry_t shmem_get_swap(struct shmem_inode_info *info, pgoff_t index)
info->i_direct[index] : (swp_entry_t){0};
}
+/*
+ * Replace item expected in radix tree by a new item, while holding tree lock.
+ */
+static int shmem_radix_tree_replace(struct address_space *mapping,
+ pgoff_t index, void *expected, void *replacement)
+{
+ void **pslot;
+ void *item = NULL;
+
+ VM_BUG_ON(!expected);
+ pslot = radix_tree_lookup_slot(&mapping->page_tree, index);
+ if (pslot)
+ item = radix_tree_deref_slot_protected(pslot,
+ &mapping->tree_lock);
+ if (item != expected)
+ return -ENOENT;
+ if (replacement)
+ radix_tree_replace_slot(pslot, replacement);
+ else
+ radix_tree_delete(&mapping->page_tree, index);
+ return 0;
+}
+
+/*
+ * Like find_get_pages, but collecting swap entries as well as pages.
+ */
+static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
+ pgoff_t start, unsigned int nr_pages,
+ struct page **pages, pgoff_t *indices)
+{
+ unsigned int i;
+ unsigned int ret;
+ unsigned int nr_found;
+
+ rcu_read_lock();
+restart:
+ nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
+ (void ***)pages, indices, start, nr_pages);
+ ret = 0;
+ for (i = 0; i < nr_found; i++) {
+ struct page *page;
+repeat:
+ page = radix_tree_deref_slot((void **)pages[i]);
+ if (unlikely(!page))
+ continue;
+ if (radix_tree_exception(page)) {
+ if (radix_tree_exceptional_entry(page))
+ goto export;
+ /* radix_tree_deref_retry(page) */
+ goto restart;
+ }
+ if (!page_cache_get_speculative(page))
+ goto repeat;
+
+ /* Has the page moved? */
+ if (unlikely(page != *((void **)pages[i]))) {
+ page_cache_release(page);
+ goto repeat;
+ }
+export:
+ indices[ret] = indices[i];
+ pages[ret] = page;
+ ret++;
+ }
+ if (unlikely(!ret && nr_found))
+ goto restart;
+ rcu_read_unlock();
+ return ret;
+}
+
+/*
+ * Remove swap entry from radix tree, free the swap and its page cache.
+ */
+static int shmem_free_swap(struct address_space *mapping,
+ pgoff_t index, void *radswap)
+{
+ int error;
+
+ spin_lock_irq(&mapping->tree_lock);
+ error = shmem_radix_tree_replace(mapping, index, radswap, NULL);
+ spin_unlock_irq(&mapping->tree_lock);
+ if (!error)
+ free_swap_and_cache(radix_to_swp_entry(radswap));
+ return error;
+}
+
+/*
+ * Pagevec may contain swap entries, so shuffle up pages before releasing.
+ */
+static void shmem_pagevec_release(struct pagevec *pvec)
+{
+ int i, j;
+
+ for (i = 0, j = 0; i < pagevec_count(pvec); i++) {
+ struct page *page = pvec->pages[i];
+ if (!radix_tree_exceptional_entry(page))
+ pvec->pages[j++] = page;
+ }
+ pvec->nr = j;
+ pagevec_release(pvec);
+}
+
+/*
+ * Remove range of pages and swap entries from radix tree, and free them.
+ */
void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
{
struct address_space *mapping = inode->i_mapping;
@@ -246,36 +351,44 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
unsigned partial = lstart & (PAGE_CACHE_SIZE - 1);
pgoff_t end = (lend >> PAGE_CACHE_SHIFT);
struct pagevec pvec;
+ pgoff_t indices[PAGEVEC_SIZE];
+ long nr_swaps_freed = 0;
pgoff_t index;
- swp_entry_t swap;
int i;
BUG_ON((lend & (PAGE_CACHE_SIZE - 1)) != (PAGE_CACHE_SIZE - 1));
pagevec_init(&pvec, 0);
index = start;
- while (index <= end && pagevec_lookup(&pvec, mapping, index,
- min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+ while (index <= end) {
+ pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
+ pvec.pages, indices);
+ if (!pvec.nr)
+ break;
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- /* We rely upon deletion not changing page->index */
- index = page->index;
+ index = indices[i];
if (index > end)
break;
- if (!trylock_page(page))
+ if (radix_tree_exceptional_entry(page)) {
+ nr_swaps_freed += !shmem_free_swap(mapping,
+ index, page);
continue;
- WARN_ON(page->index != index);
- if (PageWriteback(page)) {
- unlock_page(page);
+ }
+
+ if (!trylock_page(page))
continue;
+ if (page->mapping == mapping) {
+ VM_BUG_ON(PageWriteback(page));
+ truncate_inode_page(mapping, page);
}
- truncate_inode_page(mapping, page);
unlock_page(page);
}
- pagevec_release(&pvec);
+ shmem_pagevec_release(&pvec);
mem_cgroup_uncharge_end();
cond_resched();
index++;
@@ -295,59 +408,47 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
index = start;
for ( ; ; ) {
cond_resched();
- if (!pagevec_lookup(&pvec, mapping, index,
- min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1)) {
+ pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
+ min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
+ pvec.pages, indices);
+ if (!pvec.nr) {
if (index == start)
break;
index = start;
continue;
}
- if (index == start && pvec.pages[0]->index > end) {
- pagevec_release(&pvec);
+ if (index == start && indices[0] > end) {
+ shmem_pagevec_release(&pvec);
break;
}
mem_cgroup_uncharge_start();
for (i = 0; i < pagevec_count(&pvec); i++) {
struct page *page = pvec.pages[i];
- /* We rely upon deletion not changing page->index */
- index = page->index;
+ index = indices[i];
if (index > end)
break;
+ if (radix_tree_exceptional_entry(page)) {
+ nr_swaps_freed += !shmem_free_swap(mapping,
+ index, page);
+ continue;
+ }
+
lock_page(page);
- WARN_ON(page->index != index);
- wait_on_page_writeback(page);
- truncate_inode_page(mapping, page);
+ if (page->mapping == mapping) {
+ VM_BUG_ON(PageWriteback(page));
+ truncate_inode_page(mapping, page);
+ }
unlock_page(page);
}
- pagevec_release(&pvec);
+ shmem_pagevec_release(&pvec);
mem_cgroup_uncharge_end();
index++;
}
- if (end > SHMEM_NR_DIRECT)
- end = SHMEM_NR_DIRECT;
-
spin_lock(&info->lock);
- for (index = start; index < end; index++) {
- swap = shmem_get_swap(info, index);
- if (swap.val) {
- free_swap_and_cache(swap);
- shmem_put_swap(info, index, (swp_entry_t){0});
- info->swapped--;
- }
- }
-
- if (mapping->nrpages) {
- spin_unlock(&info->lock);
- /*
- * A page may have meanwhile sneaked in from swap.
- */
- truncate_inode_pages_range(mapping, lstart, lend);
- spin_lock(&info->lock);
- }
-
+ info->swapped -= nr_swaps_freed;
shmem_recalc_inode(inode);
spin_unlock(&info->lock);
@@ -552,11 +653,10 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
}
/*
- * Just for this patch, we have a toy implementation,
- * which can swap out only the first SHMEM_NR_DIRECT pages:
- * for simple demonstration of where we need to think about swap.
+ * Disable even the toy swapping implementation, while we convert
+ * functions one by one to having swap entries in the radix tree.
*/
- if (index >= SHMEM_NR_DIRECT)
+ if (index < ULONG_MAX)
goto redirty;
swap = get_swap_page();
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-18 19:43:28 +0000