Merge remote-tracking branch 'dhowells/netfs-lib'

Pick up David Howells' netfs helper library and the new fscache API.

Signed-off-by: Ilya Dryomov <idryomov@gmail.com>

3 files changed, 154 insertions, 19 deletions

diff --git a/mm/filemap.c b/mm/filemap.c
index 6ce832dc59e7..151090fdcf29 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1433,6 +1433,67 @@ void unlock_page(struct page *page)
 EXPORT_SYMBOL(unlock_page);
 
 /**
+ * end_page_private_2 - Clear PG_private_2 and release any waiters
+ * @page: The page
+ *
+ * Clear the PG_private_2 bit on a page and wake up any sleepers waiting for
+ * this.  The page ref held for PG_private_2 being set is released.
+ *
+ * This is, for example, used when a netfs page is being written to a local
+ * disk cache, thereby allowing writes to the cache for the same page to be
+ * serialised.
+ */
+void end_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	VM_BUG_ON_PAGE(!PagePrivate2(page), page);
+	clear_bit_unlock(PG_private_2, &page->flags);
+	wake_up_page_bit(page, PG_private_2);
+	put_page(page);
+}
+EXPORT_SYMBOL(end_page_private_2);
+
+/**
+ * wait_on_page_private_2 - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page.
+ */
+void wait_on_page_private_2(struct page *page)
+{
+	page = compound_head(page);
+	while (PagePrivate2(page))
+		wait_on_page_bit(page, PG_private_2);
+}
+EXPORT_SYMBOL(wait_on_page_private_2);
+
+/**
+ * wait_on_page_private_2_killable - Wait for PG_private_2 to be cleared on a page
+ * @page: The page to wait on
+ *
+ * Wait for PG_private_2 (aka PG_fscache) to be cleared on a page or until a
+ * fatal signal is received by the calling task.
+ *
+ * Return:
+ * - 0 if successful.
+ * - -EINTR if a fatal signal was encountered.
+ */
+int wait_on_page_private_2_killable(struct page *page)
+{
+	int ret = 0;
+
+	page = compound_head(page);
+	while (PagePrivate2(page)) {
+		ret = wait_on_page_bit_killable(page, PG_private_2);
+		if (ret < 0)
+			break;
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(wait_on_page_private_2_killable);
+
+/**
  * end_page_writeback - end writeback against a page
  * @page: the page
  */
@@ -2778,7 +2839,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 	struct file *file = vmf->vma->vm_file;
 	struct file_ra_state *ra = &file->f_ra;
 	struct address_space *mapping = file->f_mapping;
-	DEFINE_READAHEAD(ractl, file, mapping, vmf->pgoff);
+	DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff);
 	struct file *fpin = NULL;
 	unsigned int mmap_miss;
 
@@ -2790,7 +2851,7 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf)
 
 	if (vmf->vma->vm_flags & VM_SEQ_READ) {
 		fpin = maybe_unlock_mmap_for_io(vmf, fpin);
-		page_cache_sync_ra(&ractl, ra, ra->ra_pages);
+		page_cache_sync_ra(&ractl, ra->ra_pages);
 		return fpin;
 	}
 
diff --git a/mm/internal.h b/mm/internal.h
index cb3c5e0a7799..bbe900f9f095 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -51,13 +51,12 @@ void unmap_page_range(struct mmu_gather *tlb,
 
 void do_page_cache_ra(struct readahead_control *, unsigned long nr_to_read,
 		unsigned long lookahead_size);
-void force_page_cache_ra(struct readahead_control *, struct file_ra_state *,
-		unsigned long nr);
+void force_page_cache_ra(struct readahead_control *, unsigned long nr);
 static inline void force_page_cache_readahead(struct address_space *mapping,
 		struct file *file, pgoff_t index, unsigned long nr_to_read)
 {
-	DEFINE_READAHEAD(ractl, file, mapping, index);
-	force_page_cache_ra(&ractl, &file->f_ra, nr_to_read);
+	DEFINE_READAHEAD(ractl, file, &file->f_ra, mapping, index);
+	force_page_cache_ra(&ractl, nr_to_read);
 }
 
 unsigned find_lock_entries(struct address_space *mapping, pgoff_t start,
diff --git a/mm/readahead.c b/mm/readahead.c
index c5b0457415be..d589f147f4c2 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -198,8 +198,6 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 	for (i = 0; i < nr_to_read; i++) {
 		struct page *page = xa_load(&mapping->i_pages, index + i);
 
-		BUG_ON(index + i != ractl->_index + ractl->_nr_pages);
-
 		if (page && !xa_is_value(page)) {
 			/*
 			 * Page already present?  Kick off the current batch
@@ -210,6 +208,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 			 * not worth getting one just for that.
 			 */
 			read_pages(ractl, &page_pool, true);
+			i = ractl->_index + ractl->_nr_pages - index - 1;
 			continue;
 		}
 
@@ -223,6 +222,7 @@ void page_cache_ra_unbounded(struct readahead_control *ractl,
 					gfp_mask) < 0) {
 			put_page(page);
 			read_pages(ractl, &page_pool, true);
+			i = ractl->_index + ractl->_nr_pages - index - 1;
 			continue;
 		}
 		if (i == nr_to_read - lookahead_size)
@@ -272,9 +272,10 @@ void do_page_cache_ra(struct readahead_control *ractl,
  * memory at once.
  */
 void force_page_cache_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, unsigned long nr_to_read)
+		unsigned long nr_to_read)
 {
 	struct address_space *mapping = ractl->mapping;
+	struct file_ra_state *ra = ractl->ra;
 	struct backing_dev_info *bdi = inode_to_bdi(mapping->host);
 	unsigned long max_pages, index;
 
@@ -433,10 +434,10 @@ static int try_context_readahead(struct address_space *mapping,
  * A minimal readahead algorithm for trivial sequential/random reads.
  */
 static void ondemand_readahead(struct readahead_control *ractl,
-		struct file_ra_state *ra, bool hit_readahead_marker,
-		unsigned long req_size)
+		bool hit_readahead_marker, unsigned long req_size)
 {
 	struct backing_dev_info *bdi = inode_to_bdi(ractl->mapping->host);
+	struct file_ra_state *ra = ractl->ra;
 	unsigned long max_pages = ra->ra_pages;
 	unsigned long add_pages;
 	unsigned long index = readahead_index(ractl);
@@ -550,7 +551,7 @@ readit:
 }
 
 void page_cache_sync_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, unsigned long req_count)
+		unsigned long req_count)
 {
 	bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
 
@@ -560,7 +561,7 @@ void page_cache_sync_ra(struct readahead_control *ractl,
 	 * read-ahead will do the right thing and limit the read to just the
 	 * requested range, which we'll set to 1 page for this case.
 	 */
-	if (!ra->ra_pages || blk_cgroup_congested()) {
+	if (!ractl->ra->ra_pages || blk_cgroup_congested()) {
 		if (!ractl->file)
 			return;
 		req_count = 1;
@@ -569,21 +570,20 @@ void page_cache_sync_ra(struct readahead_control *ractl,
 
 	/* be dumb */
 	if (do_forced_ra) {
-		force_page_cache_ra(ractl, ra, req_count);
+		force_page_cache_ra(ractl, req_count);
 		return;
 	}
 
 	/* do read-ahead */
-	ondemand_readahead(ractl, ra, false, req_count);
+	ondemand_readahead(ractl, false, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_sync_ra);
 
 void page_cache_async_ra(struct readahead_control *ractl,
-		struct file_ra_state *ra, struct page *page,
-		unsigned long req_count)
+		struct page *page, unsigned long req_count)
 {
 	/* no read-ahead */
-	if (!ra->ra_pages)
+	if (!ractl->ra->ra_pages)
 		return;
 
 	/*
@@ -604,7 +604,7 @@ void page_cache_async_ra(struct readahead_control *ractl,
 		return;
 
 	/* do read-ahead */
-	ondemand_readahead(ractl, ra, true, req_count);
+	ondemand_readahead(ractl, true, req_count);
 }
 EXPORT_SYMBOL_GPL(page_cache_async_ra);
 
@@ -638,3 +638,78 @@ SYSCALL_DEFINE3(readahead, int, fd, loff_t, offset, size_t, count)
 {
 	return ksys_readahead(fd, offset, count);
 }
+
+/**
+ * readahead_expand - Expand a readahead request
+ * @ractl: The request to be expanded
+ * @new_start: The revised start
+ * @new_len: The revised size of the request
+ *
+ * Attempt to expand a readahead request outwards from the current size to the
+ * specified size by inserting locked pages before and after the current window
+ * to increase the size to the new window.  This may involve the insertion of
+ * THPs, in which case the window may get expanded even beyond what was
+ * requested.
+ *
+ * The algorithm will stop if it encounters a conflicting page already in the
+ * pagecache and leave a smaller expansion than requested.
+ *
+ * The caller must check for this by examining the revised @ractl object for a
+ * different expansion than was requested.
+ */
+void readahead_expand(struct readahead_control *ractl,
+		      loff_t new_start, size_t new_len)
+{
+	struct address_space *mapping = ractl->mapping;
+	struct file_ra_state *ra = ractl->ra;
+	pgoff_t new_index, new_nr_pages;
+	gfp_t gfp_mask = readahead_gfp_mask(mapping);
+
+	new_index = new_start / PAGE_SIZE;
+
+	/* Expand the leading edge downwards */
+	while (ractl->_index > new_index) {
+		unsigned long index = ractl->_index - 1;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+
+		ractl->_nr_pages++;
+		ractl->_index = page->index;
+	}
+
+	new_len += new_start - readahead_pos(ractl);
+	new_nr_pages = DIV_ROUND_UP(new_len, PAGE_SIZE);
+
+	/* Expand the trailing edge upwards */
+	while (ractl->_nr_pages < new_nr_pages) {
+		unsigned long index = ractl->_index + ractl->_nr_pages;
+		struct page *page = xa_load(&mapping->i_pages, index);
+
+		if (page && !xa_is_value(page))
+			return; /* Page apparently present */
+
+		page = __page_cache_alloc(gfp_mask);
+		if (!page)
+			return;
+		if (add_to_page_cache_lru(page, mapping, index, gfp_mask) < 0) {
+			put_page(page);
+			return;
+		}
+		ractl->_nr_pages++;
+		if (ra) {
+			ra->size++;
+			ra->async_size++;
+		}
+	}
+}
+EXPORT_SYMBOL(readahead_expand);