nilfs2: get rid of private page allocator

Previously, nilfs was cloning pages for mmapped region to freeze their
data and ensure consistency of checksum during writeback cycles.  A
private page allocator was used for this page cloning.  But, we no
longer need to do that since clear_page_dirty_for_io function sets up
pte so that vm_ops->page_mkwrite function is called right before the
mmapped pages are modified and nilfs_page_mkwrite function can safely
wait for the pages to be written back to disk.

So, this stops making a copy of mmapped pages during writeback, and
eliminates the private page allocation and deallocation functions from
nilfs.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>

1 files changed, 17 insertions, 136 deletions

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index 5deeadda908..abbfab97470 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1556,83 +1556,24 @@ static int nilfs_segctor_assign(struct nilfs_sc_info *sci, int mode)
         return 0;
 }
 
-static int
-nilfs_copy_replace_page_buffers(struct page *page, struct list_head *out)
-{
-        struct page *clone_page;
-        struct buffer_head *bh, *head, *bh2;
-        void *kaddr;
-
-        bh = head = page_buffers(page);
-
-        clone_page = nilfs_alloc_private_page(bh->b_bdev, bh->b_size, 0);
-        if (unlikely(!clone_page))
-                return -ENOMEM;
-
-        bh2 = page_buffers(clone_page);
-        kaddr = kmap_atomic(page, KM_USER0);
-        do {
-                if (list_empty(&bh->b_assoc_buffers))
-                        continue;
-                get_bh(bh2);
-                page_cache_get(clone_page); /* for each bh */
-                memcpy(bh2->b_data, kaddr + bh_offset(bh), bh2->b_size);
-                bh2->b_blocknr = bh->b_blocknr;
-                list_replace(&bh->b_assoc_buffers, &bh2->b_assoc_buffers);
-                list_add_tail(&bh->b_assoc_buffers, out);
-        } while (bh = bh->b_this_page, bh2 = bh2->b_this_page, bh != head);
-        kunmap_atomic(kaddr, KM_USER0);
-
-        if (!TestSetPageWriteback(clone_page))
-                account_page_writeback(clone_page);
-        unlock_page(clone_page);
-
-        return 0;
-}
-
-static int nilfs_test_page_to_be_frozen(struct page *page)
-{
-        struct address_space *mapping = page->mapping;
-
-        if (!mapping || !mapping->host || S_ISDIR(mapping->host->i_mode))
-                return 0;
-
-        if (page_mapped(page)) {
-                ClearPageChecked(page);
-                return 1;
-        }
-        return PageChecked(page);
-}
-
-static int nilfs_begin_page_io(struct page *page, struct list_head *out)
+static void nilfs_begin_page_io(struct page *page)
 {
         if (!page || PageWriteback(page))
                 /* For split b-tree node pages, this function may be called
                    twice.  We ignore the 2nd or later calls by this check. */
-                return 0;
+                return;
 
         lock_page(page);
         clear_page_dirty_for_io(page);
         set_page_writeback(page);
         unlock_page(page);
-
-        if (nilfs_test_page_to_be_frozen(page)) {
-                int err = nilfs_copy_replace_page_buffers(page, out);
-                if (unlikely(err))
-                        return err;
-        }
-        return 0;
 }
 
-static int nilfs_segctor_prepare_write(struct nilfs_sc_info *sci,
-                                       struct page **failed_page)
+static void nilfs_segctor_prepare_write(struct nilfs_sc_info *sci)
 {
         struct nilfs_segment_buffer *segbuf;
         struct page *bd_page = NULL, *fs_page = NULL;
-        struct list_head *list = &sci->sc_copied_buffers;
-        int err;
 
-        *failed_page = NULL;
         list_for_each_entry(segbuf, &sci->sc_segbufs, sb_list) {
                 struct buffer_head *bh;
 
@@ -1662,11 +1603,7 @@ static int nilfs_segctor_prepare_write(struct nilfs_sc_info *sci,
                                 break;
                         }
                         if (bh->b_page != fs_page) {
-                                err = nilfs_begin_page_io(fs_page, list);
-                                if (unlikely(err)) {
-                                        *failed_page = fs_page;
-                                        goto out;
-                                }
+                                nilfs_begin_page_io(fs_page);
                                 fs_page = bh->b_page;
                         }
                 }
@@ -1677,11 +1614,7 @@ static int nilfs_segctor_prepare_write(struct nilfs_sc_info *sci,
                 set_page_writeback(bd_page);
                 unlock_page(bd_page);
         }
-        err = nilfs_begin_page_io(fs_page, list);
-        if (unlikely(err))
-                *failed_page = fs_page;
- out:
-        return err;
+        nilfs_begin_page_io(fs_page);
 }
 
 static int nilfs_segctor_write(struct nilfs_sc_info *sci,
@@ -1694,24 +1627,6 @@ static int nilfs_segctor_write(struct nilfs_sc_info *sci,
         return ret;
 }
 
-static void __nilfs_end_page_io(struct page *page, int err)
-{
-        if (!err) {
-                if (!nilfs_page_buffers_clean(page))
-                        __set_page_dirty_nobuffers(page);
-                ClearPageError(page);
-        } else {
-                __set_page_dirty_nobuffers(page);
-                SetPageError(page);
-        }
-
-        if (buffer_nilfs_allocated(page_buffers(page))) {
-                if (TestClearPageWriteback(page))
-                        dec_zone_page_state(page, NR_WRITEBACK);
-        } else
-                end_page_writeback(page);
-}
-
 static void nilfs_end_page_io(struct page *page, int err)
 {
         if (!page)
@@ -1738,40 +1653,19 @@ static void nilfs_end_page_io(struct page *page, int err)
                 return;
         }
 
-        __nilfs_end_page_io(page, err);
-}
-
-static void nilfs_clear_copied_buffers(struct list_head *list, int err)
-{
-        struct buffer_head *bh, *head;
-        struct page *page;
-
-        while (!list_empty(list)) {
-                bh = list_entry(list->next, struct buffer_head,
-                                b_assoc_buffers);
-                page = bh->b_page;
-                page_cache_get(page);
-                head = bh = page_buffers(page);
-                do {
-                        if (!list_empty(&bh->b_assoc_buffers)) {
-                                list_del_init(&bh->b_assoc_buffers);
-                                if (!err) {
-                                        set_buffer_uptodate(bh);
-                                        clear_buffer_dirty(bh);
-                                        clear_buffer_delay(bh);
-                                        clear_buffer_nilfs_volatile(bh);
-                                }
-                                brelse(bh); /* for b_assoc_buffers */
-                        }
-                } while ((bh = bh->b_this_page) != head);
-
-                __nilfs_end_page_io(page, err);
-                page_cache_release(page);
+        if (!err) {
+                if (!nilfs_page_buffers_clean(page))
+                        __set_page_dirty_nobuffers(page);
+                ClearPageError(page);
+        } else {
+                __set_page_dirty_nobuffers(page);
+                SetPageError(page);
         }
+
+        end_page_writeback(page);
 }
 
-static void nilfs_abort_logs(struct list_head *logs, struct page *failed_page,
-                             int err)
+static void nilfs_abort_logs(struct list_head *logs, int err)
 {
         struct nilfs_segment_buffer *segbuf;
         struct page *bd_page = NULL, *fs_page = NULL;
@@ -1801,8 +1695,6 @@ static void nilfs_abort_logs(struct list_head *logs, struct page *failed_page,
                         }
                         if (bh->b_page != fs_page) {
                                 nilfs_end_page_io(fs_page, err);
-                                if (fs_page && fs_page == failed_page)
-                                        return;
                                 fs_page = bh->b_page;
                         }
                 }
@@ -1821,12 +1713,11 @@ static void nilfs_segctor_abort_construction(struct nilfs_sc_info *sci,
 
         list_splice_tail_init(&sci->sc_write_logs, &logs);
         ret = nilfs_wait_on_logs(&logs);
-        nilfs_abort_logs(&logs, NULL, ret ? : err);
+        nilfs_abort_logs(&logs, ret ? : err);
 
         list_splice_tail_init(&sci->sc_segbufs, &logs);
         nilfs_cancel_segusage(&logs, nilfs->ns_sufile);
         nilfs_free_incomplete_logs(&logs, nilfs);
-        nilfs_clear_copied_buffers(&sci->sc_copied_buffers, err);
 
         if (sci->sc_stage.flags & NILFS_CF_SUFREED) {
                 ret = nilfs_sufile_cancel_freev(nilfs->ns_sufile,
@@ -1920,8 +1811,6 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
 
         nilfs_end_page_io(fs_page, 0);
 
-        nilfs_clear_copied_buffers(&sci->sc_copied_buffers, 0);
-
         nilfs_drop_collected_inodes(&sci->sc_dirty_files);
 
         if (nilfs_doing_gc())
@@ -2024,7 +1913,6 @@ static void nilfs_segctor_drop_written_files(struct nilfs_sc_info *sci,
 static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
 {
         struct the_nilfs *nilfs = sci->sc_super->s_fs_info;
-        struct page *failed_page;
         int err;
 
         sci->sc_stage.scnt = NILFS_ST_INIT;
@@ -2079,11 +1967,7 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
                 nilfs_segctor_update_segusage(sci, nilfs->ns_sufile);
 
                 /* Write partial segments */
-                err = nilfs_segctor_prepare_write(sci, &failed_page);
-                if (err) {
-                        nilfs_abort_logs(&sci->sc_segbufs, failed_page, err);
-                        goto failed_to_write;
-                }
+                nilfs_segctor_prepare_write(sci);
 
                 nilfs_add_checksums_on_logs(&sci->sc_segbufs,
                                             nilfs->ns_crc_seed);
@@ -2685,7 +2569,6 @@ static struct nilfs_sc_info *nilfs_segctor_new(struct super_block *sb,
         INIT_LIST_HEAD(&sci->sc_segbufs);
         INIT_LIST_HEAD(&sci->sc_write_logs);
         INIT_LIST_HEAD(&sci->sc_gc_inodes);
-        INIT_LIST_HEAD(&sci->sc_copied_buffers);
         init_timer(&sci->sc_timer);
 
         sci->sc_interval = HZ * NILFS_SC_DEFAULT_TIMEOUT;
@@ -2739,8 +2622,6 @@ static void nilfs_segctor_destroy(struct nilfs_sc_info *sci)
         if (flag || !nilfs_segctor_confirm(sci))
                 nilfs_segctor_write_out(sci);
 
-        WARN_ON(!list_empty(&sci->sc_copied_buffers));
-
         if (!list_empty(&sci->sc_dirty_files)) {
                 nilfs_warning(sci->sc_super, __func__,
                               "dirty file(s) after the final construction\n");