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Date: Thu, 9 Jun 2022 19:33:33 +0200
From: Jan Kara <jack@...e.cz>
To: Christoph Hellwig <hch@....de>
Cc: Matthew Wilcox <willy@...radead.org>, Jan Kara <jack@...e.com>,
Dave Kleikamp <shaggy@...nel.org>, linux-ext4@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
jfs-discussion@...ts.sourceforge.net
Subject: Re: [PATCH 3/5] fs: remove the nobh helpers
On Wed 08-06-22 17:04:49, Christoph Hellwig wrote:
> All callers are gone, so remove the now dead code.
>
> Signed-off-by: Christoph Hellwig <hch@....de>
Looks good to me. Feel free to add:
Reviewed-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/buffer.c | 324 ------------------------------------
> fs/mpage.c | 25 +--
> include/linux/buffer_head.h | 8 -
> include/linux/mpage.h | 2 -
> 4 files changed, 1 insertion(+), 358 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index ce9844d7c10fa..5717d1881d2fa 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2537,330 +2537,6 @@ int block_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf,
> }
> EXPORT_SYMBOL(block_page_mkwrite);
>
> -/*
> - * nobh_write_begin()'s prereads are special: the buffer_heads are freed
> - * immediately, while under the page lock. So it needs a special end_io
> - * handler which does not touch the bh after unlocking it.
> - */
> -static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
> -{
> - __end_buffer_read_notouch(bh, uptodate);
> -}
> -
> -/*
> - * Attach the singly-linked list of buffers created by nobh_write_begin, to
> - * the page (converting it to circular linked list and taking care of page
> - * dirty races).
> - */
> -static void attach_nobh_buffers(struct page *page, struct buffer_head *head)
> -{
> - struct buffer_head *bh;
> -
> - BUG_ON(!PageLocked(page));
> -
> - spin_lock(&page->mapping->private_lock);
> - bh = head;
> - do {
> - if (PageDirty(page))
> - set_buffer_dirty(bh);
> - if (!bh->b_this_page)
> - bh->b_this_page = head;
> - bh = bh->b_this_page;
> - } while (bh != head);
> - attach_page_private(page, head);
> - spin_unlock(&page->mapping->private_lock);
> -}
> -
> -/*
> - * On entry, the page is fully not uptodate.
> - * On exit the page is fully uptodate in the areas outside (from,to)
> - * The filesystem needs to handle block truncation upon failure.
> - */
> -int nobh_write_begin(struct address_space *mapping, loff_t pos, unsigned len,
> - struct page **pagep, void **fsdata,
> - get_block_t *get_block)
> -{
> - struct inode *inode = mapping->host;
> - const unsigned blkbits = inode->i_blkbits;
> - const unsigned blocksize = 1 << blkbits;
> - struct buffer_head *head, *bh;
> - struct page *page;
> - pgoff_t index;
> - unsigned from, to;
> - unsigned block_in_page;
> - unsigned block_start, block_end;
> - sector_t block_in_file;
> - int nr_reads = 0;
> - int ret = 0;
> - int is_mapped_to_disk = 1;
> -
> - index = pos >> PAGE_SHIFT;
> - from = pos & (PAGE_SIZE - 1);
> - to = from + len;
> -
> - page = grab_cache_page_write_begin(mapping, index);
> - if (!page)
> - return -ENOMEM;
> - *pagep = page;
> - *fsdata = NULL;
> -
> - if (page_has_buffers(page)) {
> - ret = __block_write_begin(page, pos, len, get_block);
> - if (unlikely(ret))
> - goto out_release;
> - return ret;
> - }
> -
> - if (PageMappedToDisk(page))
> - return 0;
> -
> - /*
> - * Allocate buffers so that we can keep track of state, and potentially
> - * attach them to the page if an error occurs. In the common case of
> - * no error, they will just be freed again without ever being attached
> - * to the page (which is all OK, because we're under the page lock).
> - *
> - * Be careful: the buffer linked list is a NULL terminated one, rather
> - * than the circular one we're used to.
> - */
> - head = alloc_page_buffers(page, blocksize, false);
> - if (!head) {
> - ret = -ENOMEM;
> - goto out_release;
> - }
> -
> - block_in_file = (sector_t)page->index << (PAGE_SHIFT - blkbits);
> -
> - /*
> - * We loop across all blocks in the page, whether or not they are
> - * part of the affected region. This is so we can discover if the
> - * page is fully mapped-to-disk.
> - */
> - for (block_start = 0, block_in_page = 0, bh = head;
> - block_start < PAGE_SIZE;
> - block_in_page++, block_start += blocksize, bh = bh->b_this_page) {
> - int create;
> -
> - block_end = block_start + blocksize;
> - bh->b_state = 0;
> - create = 1;
> - if (block_start >= to)
> - create = 0;
> - ret = get_block(inode, block_in_file + block_in_page,
> - bh, create);
> - if (ret)
> - goto failed;
> - if (!buffer_mapped(bh))
> - is_mapped_to_disk = 0;
> - if (buffer_new(bh))
> - clean_bdev_bh_alias(bh);
> - if (PageUptodate(page)) {
> - set_buffer_uptodate(bh);
> - continue;
> - }
> - if (buffer_new(bh) || !buffer_mapped(bh)) {
> - zero_user_segments(page, block_start, from,
> - to, block_end);
> - continue;
> - }
> - if (buffer_uptodate(bh))
> - continue; /* reiserfs does this */
> - if (block_start < from || block_end > to) {
> - lock_buffer(bh);
> - bh->b_end_io = end_buffer_read_nobh;
> - submit_bh(REQ_OP_READ, 0, bh);
> - nr_reads++;
> - }
> - }
> -
> - if (nr_reads) {
> - /*
> - * The page is locked, so these buffers are protected from
> - * any VM or truncate activity. Hence we don't need to care
> - * for the buffer_head refcounts.
> - */
> - for (bh = head; bh; bh = bh->b_this_page) {
> - wait_on_buffer(bh);
> - if (!buffer_uptodate(bh))
> - ret = -EIO;
> - }
> - if (ret)
> - goto failed;
> - }
> -
> - if (is_mapped_to_disk)
> - SetPageMappedToDisk(page);
> -
> - *fsdata = head; /* to be released by nobh_write_end */
> -
> - return 0;
> -
> -failed:
> - BUG_ON(!ret);
> - /*
> - * Error recovery is a bit difficult. We need to zero out blocks that
> - * were newly allocated, and dirty them to ensure they get written out.
> - * Buffers need to be attached to the page at this point, otherwise
> - * the handling of potential IO errors during writeout would be hard
> - * (could try doing synchronous writeout, but what if that fails too?)
> - */
> - attach_nobh_buffers(page, head);
> - page_zero_new_buffers(page, from, to);
> -
> -out_release:
> - unlock_page(page);
> - put_page(page);
> - *pagep = NULL;
> -
> - return ret;
> -}
> -EXPORT_SYMBOL(nobh_write_begin);
> -
> -int nobh_write_end(struct file *file, struct address_space *mapping,
> - loff_t pos, unsigned len, unsigned copied,
> - struct page *page, void *fsdata)
> -{
> - struct inode *inode = page->mapping->host;
> - struct buffer_head *head = fsdata;
> - struct buffer_head *bh;
> - BUG_ON(fsdata != NULL && page_has_buffers(page));
> -
> - if (unlikely(copied < len) && head)
> - attach_nobh_buffers(page, head);
> - if (page_has_buffers(page))
> - return generic_write_end(file, mapping, pos, len,
> - copied, page, fsdata);
> -
> - SetPageUptodate(page);
> - set_page_dirty(page);
> - if (pos+copied > inode->i_size) {
> - i_size_write(inode, pos+copied);
> - mark_inode_dirty(inode);
> - }
> -
> - unlock_page(page);
> - put_page(page);
> -
> - while (head) {
> - bh = head;
> - head = head->b_this_page;
> - free_buffer_head(bh);
> - }
> -
> - return copied;
> -}
> -EXPORT_SYMBOL(nobh_write_end);
> -
> -/*
> - * nobh_writepage() - based on block_full_write_page() except
> - * that it tries to operate without attaching bufferheads to
> - * the page.
> - */
> -int nobh_writepage(struct page *page, get_block_t *get_block,
> - struct writeback_control *wbc)
> -{
> - struct inode * const inode = page->mapping->host;
> - loff_t i_size = i_size_read(inode);
> - const pgoff_t end_index = i_size >> PAGE_SHIFT;
> - unsigned offset;
> - int ret;
> -
> - /* Is the page fully inside i_size? */
> - if (page->index < end_index)
> - goto out;
> -
> - /* Is the page fully outside i_size? (truncate in progress) */
> - offset = i_size & (PAGE_SIZE-1);
> - if (page->index >= end_index+1 || !offset) {
> - unlock_page(page);
> - return 0; /* don't care */
> - }
> -
> - /*
> - * The page straddles i_size. It must be zeroed out on each and every
> - * writepage invocation because it may be mmapped. "A file is mapped
> - * in multiples of the page size. For a file that is not a multiple of
> - * the page size, the remaining memory is zeroed when mapped, and
> - * writes to that region are not written out to the file."
> - */
> - zero_user_segment(page, offset, PAGE_SIZE);
> -out:
> - ret = mpage_writepage(page, get_block, wbc);
> - if (ret == -EAGAIN)
> - ret = __block_write_full_page(inode, page, get_block, wbc,
> - end_buffer_async_write);
> - return ret;
> -}
> -EXPORT_SYMBOL(nobh_writepage);
> -
> -int nobh_truncate_page(struct address_space *mapping,
> - loff_t from, get_block_t *get_block)
> -{
> - pgoff_t index = from >> PAGE_SHIFT;
> - struct inode *inode = mapping->host;
> - unsigned blocksize = i_blocksize(inode);
> - struct folio *folio;
> - struct buffer_head map_bh;
> - size_t offset;
> - sector_t iblock;
> - int err;
> -
> - /* Block boundary? Nothing to do */
> - if (!(from & (blocksize - 1)))
> - return 0;
> -
> - folio = __filemap_get_folio(mapping, index, FGP_LOCK | FGP_CREAT,
> - mapping_gfp_mask(mapping));
> - err = -ENOMEM;
> - if (!folio)
> - goto out;
> -
> - if (folio_buffers(folio))
> - goto has_buffers;
> -
> - iblock = from >> inode->i_blkbits;
> - map_bh.b_size = blocksize;
> - map_bh.b_state = 0;
> - err = get_block(inode, iblock, &map_bh, 0);
> - if (err)
> - goto unlock;
> - /* unmapped? It's a hole - nothing to do */
> - if (!buffer_mapped(&map_bh))
> - goto unlock;
> -
> - /* Ok, it's mapped. Make sure it's up-to-date */
> - if (!folio_test_uptodate(folio)) {
> - err = mapping->a_ops->read_folio(NULL, folio);
> - if (err) {
> - folio_put(folio);
> - goto out;
> - }
> - folio_lock(folio);
> - if (!folio_test_uptodate(folio)) {
> - err = -EIO;
> - goto unlock;
> - }
> - if (folio_buffers(folio))
> - goto has_buffers;
> - }
> - offset = offset_in_folio(folio, from);
> - folio_zero_segment(folio, offset, round_up(offset, blocksize));
> - folio_mark_dirty(folio);
> - err = 0;
> -
> -unlock:
> - folio_unlock(folio);
> - folio_put(folio);
> -out:
> - return err;
> -
> -has_buffers:
> - folio_unlock(folio);
> - folio_put(folio);
> - return block_truncate_page(mapping, from, get_block);
> -}
> -EXPORT_SYMBOL(nobh_truncate_page);
> -
> int block_truncate_page(struct address_space *mapping,
> loff_t from, get_block_t *get_block)
> {
> diff --git a/fs/mpage.c b/fs/mpage.c
> index 0d25f44f5707c..31a97a0acf5f5 100644
> --- a/fs/mpage.c
> +++ b/fs/mpage.c
> @@ -402,7 +402,6 @@ struct mpage_data {
> struct bio *bio;
> sector_t last_block_in_bio;
> get_block_t *get_block;
> - unsigned use_writepage;
> };
>
> /*
> @@ -622,15 +621,10 @@ static int __mpage_writepage(struct page *page, struct writeback_control *wbc,
> if (bio)
> bio = mpage_bio_submit(bio);
>
> - if (mpd->use_writepage) {
> - ret = mapping->a_ops->writepage(page, wbc);
> - } else {
> - ret = -EAGAIN;
> - goto out;
> - }
> /*
> * The caller has a ref on the inode, so *mapping is stable
> */
> + ret = mapping->a_ops->writepage(page, wbc);
> mapping_set_error(mapping, ret);
> out:
> mpd->bio = bio;
> @@ -672,7 +666,6 @@ mpage_writepages(struct address_space *mapping,
> .bio = NULL,
> .last_block_in_bio = 0,
> .get_block = get_block,
> - .use_writepage = 1,
> };
>
> ret = write_cache_pages(mapping, wbc, __mpage_writepage, &mpd);
> @@ -683,19 +676,3 @@ mpage_writepages(struct address_space *mapping,
> return ret;
> }
> EXPORT_SYMBOL(mpage_writepages);
> -
> -int mpage_writepage(struct page *page, get_block_t get_block,
> - struct writeback_control *wbc)
> -{
> - struct mpage_data mpd = {
> - .bio = NULL,
> - .last_block_in_bio = 0,
> - .get_block = get_block,
> - .use_writepage = 0,
> - };
> - int ret = __mpage_writepage(page, wbc, &mpd);
> - if (mpd.bio)
> - mpage_bio_submit(mpd.bio);
> - return ret;
> -}
> -EXPORT_SYMBOL(mpage_writepage);
> diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
> index b0366c89d6a4d..61afb81cfdaea 100644
> --- a/include/linux/buffer_head.h
> +++ b/include/linux/buffer_head.h
> @@ -258,14 +258,6 @@ static inline vm_fault_t block_page_mkwrite_return(int err)
> }
> sector_t generic_block_bmap(struct address_space *, sector_t, get_block_t *);
> int block_truncate_page(struct address_space *, loff_t, get_block_t *);
> -int nobh_write_begin(struct address_space *, loff_t, unsigned len,
> - struct page **, void **, get_block_t*);
> -int nobh_write_end(struct file *, struct address_space *,
> - loff_t, unsigned, unsigned,
> - struct page *, void *);
> -int nobh_truncate_page(struct address_space *, loff_t, get_block_t *);
> -int nobh_writepage(struct page *page, get_block_t *get_block,
> - struct writeback_control *wbc);
>
> #ifdef CONFIG_MIGRATION
> extern int buffer_migrate_folio(struct address_space *,
> diff --git a/include/linux/mpage.h b/include/linux/mpage.h
> index 43986f7ec4dd3..1bdc39daac0a3 100644
> --- a/include/linux/mpage.h
> +++ b/include/linux/mpage.h
> @@ -19,7 +19,5 @@ void mpage_readahead(struct readahead_control *, get_block_t get_block);
> int mpage_read_folio(struct folio *folio, get_block_t get_block);
> int mpage_writepages(struct address_space *mapping,
> struct writeback_control *wbc, get_block_t get_block);
> -int mpage_writepage(struct page *page, get_block_t *get_block,
> - struct writeback_control *wbc);
>
> #endif
> --
> 2.30.2
>
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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