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Date: Thu, 15 Dec 2022 09:48:41 +0800
From: Chao Yu <chao@...nel.org>
To: "Vishal Moola (Oracle)" <vishal.moola@...il.com>
Cc: linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net, linux-mm@...ck.org,
fengnanchang@...il.com, linux-fsdevel@...r.kernel.org
Subject: Re: [RFC PATCH] f2fs: Convert f2fs_write_cache_pages() to use
filemap_get_folios_tag()
On 2022/12/13 3:13, Vishal Moola (Oracle) wrote:
> Converted the function to use a folio_batch instead of pagevec. This is in
> preparation for the removal of find_get_pages_range_tag().
>
> Also modified f2fs_all_cluster_page_ready to take in a folio_batch instead
> of pagevec. This does NOT support large folios. The function currently
> only utilizes folios of size 1 so this shouldn't cause any issues right
> now.
>
> This version of the patch limits the number of pages fetched to
> F2FS_ONSTACK_PAGES. If that ever happens, update the start index here
> since filemap_get_folios_tag() updates the index to be after the last
> found folio, not necessarily the last used page.
>
> Signed-off-by: Vishal Moola (Oracle) <vishal.moola@...il.com>
> ---
>
> Let me know if you prefer this version and I'll include it in v5
> of the patch series when I rebase it after the merge window.
>
> ---
> fs/f2fs/data.c | 86 ++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 59 insertions(+), 27 deletions(-)
>
> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> index a71e818cd67b..1703e353f0e0 100644
> --- a/fs/f2fs/data.c
> +++ b/fs/f2fs/data.c
> @@ -2939,6 +2939,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> int ret = 0;
> int done = 0, retry = 0;
> struct page *pages[F2FS_ONSTACK_PAGES];
> + struct folio_batch fbatch;
> struct f2fs_sb_info *sbi = F2FS_M_SB(mapping);
> struct bio *bio = NULL;
> sector_t last_block;
> @@ -2959,6 +2960,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> .private = NULL,
> };
> #endif
> + int nr_folios, p, idx;
> int nr_pages;
> pgoff_t index;
> pgoff_t end; /* Inclusive */
> @@ -2969,6 +2971,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> int submitted = 0;
> int i;
>
> + folio_batch_init(&fbatch);
> +
> if (get_dirty_pages(mapping->host) <=
> SM_I(F2FS_M_SB(mapping))->min_hot_blocks)
> set_inode_flag(mapping->host, FI_HOT_DATA);
> @@ -2994,13 +2998,38 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> tag_pages_for_writeback(mapping, index, end);
> done_index = index;
> while (!done && !retry && (index <= end)) {
> - nr_pages = find_get_pages_range_tag(mapping, &index, end,
> - tag, F2FS_ONSTACK_PAGES, pages);
> - if (nr_pages == 0)
> + nr_pages = 0;
> +again:
> + nr_folios = filemap_get_folios_tag(mapping, &index, end,
> + tag, &fbatch);
> + if (nr_folios == 0) {
> + if (nr_pages)
> + goto write;
> break;
> + }
>
> + for (i = 0; i < nr_folios; i++) {
> + struct folio* folio = fbatch.folios[i];
> +
> + idx = 0;
> + p = folio_nr_pages(folio);
> +add_more:
> + pages[nr_pages] = folio_page(folio,idx);
> + folio_ref_inc(folio);
It looks if CONFIG_LRU_GEN is not set, folio_ref_inc() does nothing. For those
folios recorded in pages array, we need to call folio_get() here to add one more
reference on each of them?
> + if (++nr_pages == F2FS_ONSTACK_PAGES) {
> + index = folio->index + idx + 1;
> + folio_batch_release(&fbatch);
Otherwise after folio_batch_release(), it may cause use-after-free issue
when accessing pages array? Or am I missing something?
> + goto write;
> + }
> + if (++idx < p)
> + goto add_more;
> + }
> + folio_batch_release(&fbatch);
> + goto again;
> +write:
> for (i = 0; i < nr_pages; i++) {
> struct page *page = pages[i];
> + struct folio *folio = page_folio(page);
> bool need_readd;
> readd:
> need_readd = false;
> @@ -3017,7 +3046,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> }
>
> if (!f2fs_cluster_can_merge_page(&cc,
> - page->index)) {
> + folio->index)) {
> ret = f2fs_write_multi_pages(&cc,
> &submitted, wbc, io_type);
> if (!ret)
> @@ -3026,27 +3055,28 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> }
>
> if (unlikely(f2fs_cp_error(sbi)))
> - goto lock_page;
> + goto lock_folio;
>
> if (!f2fs_cluster_is_empty(&cc))
> - goto lock_page;
> + goto lock_folio;
>
> if (f2fs_all_cluster_page_ready(&cc,
> pages, i, nr_pages, true))
> - goto lock_page;
> + goto lock_folio;
>
> ret2 = f2fs_prepare_compress_overwrite(
> inode, &pagep,
> - page->index, &fsdata);
> + folio->index, &fsdata);
> if (ret2 < 0) {
> ret = ret2;
> done = 1;
> break;
> } else if (ret2 &&
> (!f2fs_compress_write_end(inode,
> - fsdata, page->index, 1) ||
> + fsdata, folio->index, 1) ||
> !f2fs_all_cluster_page_ready(&cc,
> - pages, i, nr_pages, false))) {
> + pages, i, nr_pages,
> + false))) {
> retry = 1;
> break;
> }
> @@ -3059,46 +3089,47 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> break;
> }
> #ifdef CONFIG_F2FS_FS_COMPRESSION
> -lock_page:
> +lock_folio:
> #endif
> - done_index = page->index;
> + done_index = folio->index;
> retry_write:
> - lock_page(page);
> + folio_lock(folio);
>
> - if (unlikely(page->mapping != mapping)) {
> + if (unlikely(folio->mapping != mapping)) {
> continue_unlock:
> - unlock_page(page);
> + folio_unlock(folio);
> continue;
> }
>
> - if (!PageDirty(page)) {
> + if (!folio_test_dirty(folio)) {
> /* someone wrote it for us */
> goto continue_unlock;
> }
>
> - if (PageWriteback(page)) {
> + if (folio_test_writeback(folio)) {
> if (wbc->sync_mode != WB_SYNC_NONE)
> - f2fs_wait_on_page_writeback(page,
> + f2fs_wait_on_page_writeback(
> + &folio->page,
> DATA, true, true);
> else
> goto continue_unlock;
> }
>
> - if (!clear_page_dirty_for_io(page))
> + if (!folio_clear_dirty_for_io(folio))
> goto continue_unlock;
>
> #ifdef CONFIG_F2FS_FS_COMPRESSION
> if (f2fs_compressed_file(inode)) {
> - get_page(page);
> - f2fs_compress_ctx_add_page(&cc, page);
> + folio_get(folio);
> + f2fs_compress_ctx_add_page(&cc, &folio->page);
> continue;
> }
> #endif
> - ret = f2fs_write_single_data_page(page, &submitted,
> - &bio, &last_block, wbc, io_type,
> - 0, true);
> + ret = f2fs_write_single_data_page(&folio->page,
> + &submitted, &bio, &last_block,
> + wbc, io_type, 0, true);
> if (ret == AOP_WRITEPAGE_ACTIVATE)
> - unlock_page(page);
> + folio_unlock(folio);
> #ifdef CONFIG_F2FS_FS_COMPRESSION
> result:
> #endif
> @@ -3122,7 +3153,8 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> }
> goto next;
> }
> - done_index = page->index + 1;
> + done_index = folio->index +
> + folio_nr_pages(folio);
> done = 1;
> break;
> }
> @@ -3136,7 +3168,7 @@ static int f2fs_write_cache_pages(struct address_space *mapping,
> if (need_readd)
> goto readd;
> }
> - release_pages(pages, nr_pages);
> + release_pages(pages,nr_pages);
No need to change?
Thanks,
> cond_resched();
> }
> #ifdef CONFIG_F2FS_FS_COMPRESSION
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