char value[0];
};
+/*
+ * shmem_fallocate and shmem_writepage communicate via inode->i_private
+ * (with i_mutex making sure that it has only one user at a time):
+ * we would prefer not to enlarge the shmem inode just for that.
+ */
+struct shmem_falloc {
+ pgoff_t start; /* start of range currently being fallocated */
+ pgoff_t next; /* the next page offset to be fallocated */
+ pgoff_t nr_falloced; /* how many new pages have been fallocated */
+ pgoff_t nr_unswapped; /* how often writepage refused to swap out */
+};
+
/* Flag allocation requirements to shmem_getpage */
enum sgp_type {
SGP_READ, /* don't exceed i_size, don't allocate page */
mutex_lock(&shmem_swaplist_mutex);
/*
* We needed to drop mutex to make that restrictive page
- * allocation; but the inode might already be freed by now,
- * and we cannot refer to inode or mapping or info to check.
- * However, we do hold page lock on the PageSwapCache page,
- * so can check if that still has our reference remaining.
+ * allocation, but the inode might have been freed while we
+ * dropped it: although a racing shmem_evict_inode() cannot
+ * complete without emptying the radix_tree, our page lock
+ * on this swapcache page is not enough to prevent that -
+ * free_swap_and_cache() of our swap entry will only
+ * trylock_page(), removing swap from radix_tree whatever.
+ *
+ * We must not proceed to shmem_add_to_page_cache() if the
+ * inode has been freed, but of course we cannot rely on
+ * inode or mapping or info to check that. However, we can
+ * safely check if our swap entry is still in use (and here
+ * it can't have got reused for another page): if it's still
+ * in use, then the inode cannot have been freed yet, and we
+ * can safely proceed (if it's no longer in use, that tells
+ * nothing about the inode, but we don't need to unuse swap).
*/
if (!page_swapcount(*pagep))
error = -ENOENT;
/*
* There's a faint possibility that swap page was replaced before
- * caller locked it: it will come back later with the right page.
+ * caller locked it: caller will come back later with the right page.
*/
- if (unlikely(!PageSwapCache(page)))
+ if (unlikely(!PageSwapCache(page) || page_private(page) != swap.val))
goto out;
/*
* This is somewhat ridiculous, but without plumbing a SWAP_MAP_FALLOC
* value into swapfile.c, the only way we can correctly account for a
* fallocated page arriving here is now to initialize it and write it.
+ *
+ * That's okay for a page already fallocated earlier, but if we have
+ * not yet completed the fallocation, then (a) we want to keep track
+ * of this page in case we have to undo it, and (b) it may not be a
+ * good idea to continue anyway, once we're pushing into swap. So
+ * reactivate the page, and let shmem_fallocate() quit when too many.
*/
if (!PageUptodate(page)) {
+ if (inode->i_private) {
+ struct shmem_falloc *shmem_falloc;
+ spin_lock(&inode->i_lock);
+ shmem_falloc = inode->i_private;
+ if (shmem_falloc &&
+ index >= shmem_falloc->start &&
+ index < shmem_falloc->next)
+ shmem_falloc->nr_unswapped++;
+ else
+ shmem_falloc = NULL;
+ spin_unlock(&inode->i_lock);
+ if (shmem_falloc)
+ goto redirty;
+ }
clear_highpage(page);
flush_dcache_page(page);
SetPageUptodate(page);
newpage = shmem_alloc_page(gfp, info, index);
if (!newpage)
return -ENOMEM;
- VM_BUG_ON(shmem_should_replace_page(newpage, gfp));
- *pagep = newpage;
page_cache_get(newpage);
copy_highpage(newpage, oldpage);
+ flush_dcache_page(newpage);
- VM_BUG_ON(!PageLocked(oldpage));
__set_page_locked(newpage);
- VM_BUG_ON(!PageUptodate(oldpage));
SetPageUptodate(newpage);
- VM_BUG_ON(!PageSwapBacked(oldpage));
SetPageSwapBacked(newpage);
- VM_BUG_ON(!swap_index);
set_page_private(newpage, swap_index);
- VM_BUG_ON(!PageSwapCache(oldpage));
SetPageSwapCache(newpage);
/*
spin_lock_irq(&swap_mapping->tree_lock);
error = shmem_radix_tree_replace(swap_mapping, swap_index, oldpage,
newpage);
- __inc_zone_page_state(newpage, NR_FILE_PAGES);
- __dec_zone_page_state(oldpage, NR_FILE_PAGES);
+ if (!error) {
+ __inc_zone_page_state(newpage, NR_FILE_PAGES);
+ __dec_zone_page_state(oldpage, NR_FILE_PAGES);
+ }
spin_unlock_irq(&swap_mapping->tree_lock);
- BUG_ON(error);
- mem_cgroup_replace_page_cache(oldpage, newpage);
- lru_cache_add_anon(newpage);
+ if (unlikely(error)) {
+ /*
+ * Is this possible? I think not, now that our callers check
+ * both PageSwapCache and page_private after getting page lock;
+ * but be defensive. Reverse old to newpage for clear and free.
+ */
+ oldpage = newpage;
+ } else {
+ mem_cgroup_replace_page_cache(oldpage, newpage);
+ lru_cache_add_anon(newpage);
+ *pagep = newpage;
+ }
ClearPageSwapCache(oldpage);
set_page_private(oldpage, 0);
unlock_page(oldpage);
page_cache_release(oldpage);
page_cache_release(oldpage);
- return 0;
+ return error;
}
/*
/* We have to do this with page locked to prevent races */
lock_page(page);
- if (!PageSwapCache(page) || page->mapping) {
+ if (!PageSwapCache(page) || page_private(page) != swap.val ||
+ page->mapping) {
error = -EEXIST; /* try again */
goto failed;
}
return error;
}
+/*
+ * llseek SEEK_DATA or SEEK_HOLE through the radix_tree.
+ */
+static pgoff_t shmem_seek_hole_data(struct address_space *mapping,
+ pgoff_t index, pgoff_t end, int origin)
+{
+ struct page *page;
+ struct pagevec pvec;
+ pgoff_t indices[PAGEVEC_SIZE];
+ bool done = false;
+ int i;
+
+ pagevec_init(&pvec, 0);
+ pvec.nr = 1; /* start small: we may be there already */
+ while (!done) {
+ pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
+ pvec.nr, pvec.pages, indices);
+ if (!pvec.nr) {
+ if (origin == SEEK_DATA)
+ index = end;
+ break;
+ }
+ for (i = 0; i < pvec.nr; i++, index++) {
+ if (index < indices[i]) {
+ if (origin == SEEK_HOLE) {
+ done = true;
+ break;
+ }
+ index = indices[i];
+ }
+ page = pvec.pages[i];
+ if (page && !radix_tree_exceptional_entry(page)) {
+ if (!PageUptodate(page))
+ page = NULL;
+ }
+ if (index >= end ||
+ (page && origin == SEEK_DATA) ||
+ (!page && origin == SEEK_HOLE)) {
+ done = true;
+ break;
+ }
+ }
+ shmem_deswap_pagevec(&pvec);
+ pagevec_release(&pvec);
+ pvec.nr = PAGEVEC_SIZE;
+ cond_resched();
+ }
+ return index;
+}
+
+static loff_t shmem_file_llseek(struct file *file, loff_t offset, int origin)
+{
+ struct address_space *mapping;
+ struct inode *inode;
+ pgoff_t start, end;
+ loff_t new_offset;
+
+ if (origin != SEEK_DATA && origin != SEEK_HOLE)
+ return generic_file_llseek_size(file, offset, origin,
+ MAX_LFS_FILESIZE);
+ mapping = file->f_mapping;
+ inode = mapping->host;
+ mutex_lock(&inode->i_mutex);
+ /* We're holding i_mutex so we can access i_size directly */
+
+ if (offset < 0)
+ offset = -EINVAL;
+ else if (offset >= inode->i_size)
+ offset = -ENXIO;
+ else {
+ start = offset >> PAGE_CACHE_SHIFT;
+ end = (inode->i_size + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
+ new_offset = shmem_seek_hole_data(mapping, start, end, origin);
+ new_offset <<= PAGE_CACHE_SHIFT;
+ if (new_offset > offset) {
+ if (new_offset < inode->i_size)
+ offset = new_offset;
+ else if (origin == SEEK_DATA)
+ offset = -ENXIO;
+ else
+ offset = inode->i_size;
+ }
+ }
+
+ if (offset >= 0 && offset != file->f_pos) {
+ file->f_pos = offset;
+ file->f_version = 0;
+ }
+ mutex_unlock(&inode->i_mutex);
+ return offset;
+}
+
static long shmem_fallocate(struct file *file, int mode, loff_t offset,
loff_t len)
{
struct inode *inode = file->f_path.dentry->d_inode;
struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
+ struct shmem_falloc shmem_falloc;
pgoff_t start, index, end;
int error;
goto out;
}
+ shmem_falloc.start = start;
+ shmem_falloc.next = start;
+ shmem_falloc.nr_falloced = 0;
+ shmem_falloc.nr_unswapped = 0;
+ spin_lock(&inode->i_lock);
+ inode->i_private = &shmem_falloc;
+ spin_unlock(&inode->i_lock);
+
for (index = start; index < end; index++) {
struct page *page;
*/
if (signal_pending(current))
error = -EINTR;
+ else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
+ error = -ENOMEM;
else
error = shmem_getpage(inode, index, &page, SGP_FALLOC,
NULL);
shmem_undo_range(inode,
(loff_t)start << PAGE_CACHE_SHIFT,
(loff_t)index << PAGE_CACHE_SHIFT, true);
- goto ctime;
+ goto undone;
}
+ /*
+ * Inform shmem_writepage() how far we have reached.
+ * No need for lock or barrier: we have the page lock.
+ */
+ shmem_falloc.next++;
+ if (!PageUptodate(page))
+ shmem_falloc.nr_falloced++;
+
/*
* If !PageUptodate, leave it that way so that freeable pages
* can be recognized if we need to rollback on error later.
if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
i_size_write(inode, offset + len);
-ctime:
inode->i_ctime = CURRENT_TIME;
+undone:
+ spin_lock(&inode->i_lock);
+ inode->i_private = NULL;
+ spin_unlock(&inode->i_lock);
out:
mutex_unlock(&inode->i_mutex);
return error;
return dentry;
}
-static int shmem_encode_fh(struct dentry *dentry, __u32 *fh, int *len,
- int connectable)
+static int shmem_encode_fh(struct inode *inode, __u32 *fh, int *len,
+ struct inode *parent)
{
- struct inode *inode = dentry->d_inode;
-
if (*len < 3) {
*len = 3;
return 255;
static const struct file_operations shmem_file_operations = {
.mmap = shmem_mmap,
#ifdef CONFIG_TMPFS
- .llseek = generic_file_llseek,
+ .llseek = shmem_file_llseek,
.read = do_sync_read,
.write = do_sync_write,
.aio_read = shmem_file_aio_read,
projects / mirror_ubuntu-zesty-kernel.git / blobdiff