From 0058f9658c94037173f7603fc8bae2007cc10253 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Thu, 11 Apr 2013 23:48:32 -0400 Subject: [PATCH] ext4: make ext4_bio_write_page() use BH_Async_Write flags So far ext4_bio_write_page() attached all the pages to ext4_io_end structure. This makes that structure pretty heavy (1 KB for pointers + 16 bytes per page attached to the bio). Also later we would like to share ext4_io_end structure among several bios in case IO to a single extent needs to be split among several bios and pointing to pages from ext4_io_end makes this complex. We remove page pointers from ext4_io_end and use pointers from bio itself instead. This isn't as easy when blocksize < pagesize because then we can have several bios in flight for a single page and we have to be careful when to call end_page_writeback(). However this is a known problem already solved by block_write_full_page() / end_buffer_async_write() so we mimic its behavior here. We mark buffers going to disk with BH_Async_Write flag and in ext4_bio_end_io() we check whether there are any buffers with BH_Async_Write flag left. If there are not, we can call end_page_writeback(). Signed-off-by: Jan Kara Signed-off-by: "Theodore Ts'o" Reviewed-by: Dmitry Monakhov Reviewed-by: Zheng Liu --- fs/ext4/ext4.h | 14 ---- fs/ext4/page-io.c | 163 ++++++++++++++++++++++------------------------ 2 files changed, 77 insertions(+), 100 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 75b2326b04c..3b41d4ae6f9 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -198,19 +198,8 @@ struct mpage_da_data { #define EXT4_IO_END_ERROR 0x0002 #define EXT4_IO_END_DIRECT 0x0004 -struct ext4_io_page { - struct page *p_page; - atomic_t p_count; -}; - -#define MAX_IO_PAGES 128 - /* * For converting uninitialized extents on a work queue. - * - * 'page' is only used from the writepage() path; 'pages' is only used for - * buffered writes; they are used to keep page references until conversion - * takes place. For AIO/DIO, neither field is filled in. */ typedef struct ext4_io_end { struct list_head list; /* per-file finished IO list */ @@ -220,15 +209,12 @@ typedef struct ext4_io_end { ssize_t size; /* size of the extent */ struct kiocb *iocb; /* iocb struct for AIO */ int result; /* error value for AIO */ - int num_io_pages; /* for writepages() */ - struct ext4_io_page *pages[MAX_IO_PAGES]; /* for writepages() */ } ext4_io_end_t; struct ext4_io_submit { int io_op; struct bio *io_bio; ext4_io_end_t *io_end; - struct ext4_io_page *io_page; sector_t io_next_block; }; diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c index 047a6de04a0..1d98fcfc2ff 100644 --- a/fs/ext4/page-io.c +++ b/fs/ext4/page-io.c @@ -29,25 +29,19 @@ #include "xattr.h" #include "acl.h" -static struct kmem_cache *io_page_cachep, *io_end_cachep; +static struct kmem_cache *io_end_cachep; int __init ext4_init_pageio(void) { - io_page_cachep = KMEM_CACHE(ext4_io_page, SLAB_RECLAIM_ACCOUNT); - if (io_page_cachep == NULL) - return -ENOMEM; io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT); - if (io_end_cachep == NULL) { - kmem_cache_destroy(io_page_cachep); + if (io_end_cachep == NULL) return -ENOMEM; - } return 0; } void ext4_exit_pageio(void) { kmem_cache_destroy(io_end_cachep); - kmem_cache_destroy(io_page_cachep); } /* @@ -67,15 +61,6 @@ void ext4_ioend_shutdown(struct inode *inode) cancel_work_sync(&EXT4_I(inode)->i_unwritten_work); } -static void put_io_page(struct ext4_io_page *io_page) -{ - if (atomic_dec_and_test(&io_page->p_count)) { - end_page_writeback(io_page->p_page); - put_page(io_page->p_page); - kmem_cache_free(io_page_cachep, io_page); - } -} - void ext4_free_io_end(ext4_io_end_t *io) { int i; @@ -84,9 +69,6 @@ void ext4_free_io_end(ext4_io_end_t *io) BUG_ON(!list_empty(&io->list)); BUG_ON(io->flag & EXT4_IO_END_UNWRITTEN); - for (i = 0; i < io->num_io_pages; i++) - put_io_page(io->pages[i]); - io->num_io_pages = 0; if (atomic_dec_and_test(&EXT4_I(io->inode)->i_ioend_count)) wake_up_all(ext4_ioend_wq(io->inode)); kmem_cache_free(io_end_cachep, io); @@ -243,45 +225,56 @@ static void ext4_end_bio(struct bio *bio, int error) ext4_io_end_t *io_end = bio->bi_private; struct inode *inode; int i; + int blocksize; sector_t bi_sector = bio->bi_sector; BUG_ON(!io_end); + inode = io_end->inode; + blocksize = 1 << inode->i_blkbits; bio->bi_private = NULL; bio->bi_end_io = NULL; if (test_bit(BIO_UPTODATE, &bio->bi_flags)) error = 0; - bio_put(bio); - - for (i = 0; i < io_end->num_io_pages; i++) { - struct page *page = io_end->pages[i]->p_page; + for (i = 0; i < bio->bi_vcnt; i++) { + struct bio_vec *bvec = &bio->bi_io_vec[i]; + struct page *page = bvec->bv_page; struct buffer_head *bh, *head; - loff_t offset; - loff_t io_end_offset; + unsigned bio_start = bvec->bv_offset; + unsigned bio_end = bio_start + bvec->bv_len; + unsigned under_io = 0; + unsigned long flags; + + if (!page) + continue; if (error) { SetPageError(page); set_bit(AS_EIO, &page->mapping->flags); - head = page_buffers(page); - BUG_ON(!head); - - io_end_offset = io_end->offset + io_end->size; - - offset = (sector_t) page->index << PAGE_CACHE_SHIFT; - bh = head; - do { - if ((offset >= io_end->offset) && - (offset+bh->b_size <= io_end_offset)) - buffer_io_error(bh); - - offset += bh->b_size; - bh = bh->b_this_page; - } while (bh != head); } - - put_io_page(io_end->pages[i]); + bh = head = page_buffers(page); + /* + * We check all buffers in the page under BH_Uptodate_Lock + * to avoid races with other end io clearing async_write flags + */ + local_irq_save(flags); + bit_spin_lock(BH_Uptodate_Lock, &head->b_state); + do { + if (bh_offset(bh) < bio_start || + bh_offset(bh) + blocksize > bio_end) { + if (buffer_async_write(bh)) + under_io++; + continue; + } + clear_buffer_async_write(bh); + if (error) + buffer_io_error(bh); + } while ((bh = bh->b_this_page) != head); + bit_spin_unlock(BH_Uptodate_Lock, &head->b_state); + local_irq_restore(flags); + if (!under_io) + end_page_writeback(page); } - io_end->num_io_pages = 0; - inode = io_end->inode; + bio_put(bio); if (error) { io_end->flag |= EXT4_IO_END_ERROR; @@ -345,7 +338,6 @@ static int io_submit_init(struct ext4_io_submit *io, } static int io_submit_add_bh(struct ext4_io_submit *io, - struct ext4_io_page *io_page, struct inode *inode, struct writeback_control *wbc, struct buffer_head *bh) @@ -353,11 +345,6 @@ static int io_submit_add_bh(struct ext4_io_submit *io, ext4_io_end_t *io_end; int ret; - if (buffer_new(bh)) { - clear_buffer_new(bh); - unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); - } - if (io->io_bio && bh->b_blocknr != io->io_next_block) { submit_and_retry: ext4_io_submit(io); @@ -368,9 +355,6 @@ submit_and_retry: return ret; } io_end = io->io_end; - if ((io_end->num_io_pages >= MAX_IO_PAGES) && - (io_end->pages[io_end->num_io_pages-1] != io_page)) - goto submit_and_retry; if (buffer_uninit(bh)) ext4_set_io_unwritten_flag(inode, io_end); io->io_end->size += bh->b_size; @@ -378,11 +362,6 @@ submit_and_retry: ret = bio_add_page(io->io_bio, bh->b_page, bh->b_size, bh_offset(bh)); if (ret != bh->b_size) goto submit_and_retry; - if ((io_end->num_io_pages == 0) || - (io_end->pages[io_end->num_io_pages-1] != io_page)) { - io_end->pages[io_end->num_io_pages++] = io_page; - atomic_inc(&io_page->p_count); - } return 0; } @@ -392,33 +371,29 @@ int ext4_bio_write_page(struct ext4_io_submit *io, struct writeback_control *wbc) { struct inode *inode = page->mapping->host; - unsigned block_start, block_end, blocksize; - struct ext4_io_page *io_page; + unsigned block_start, blocksize; struct buffer_head *bh, *head; int ret = 0; + int nr_submitted = 0; blocksize = 1 << inode->i_blkbits; BUG_ON(!PageLocked(page)); BUG_ON(PageWriteback(page)); - io_page = kmem_cache_alloc(io_page_cachep, GFP_NOFS); - if (!io_page) { - redirty_page_for_writepage(wbc, page); - unlock_page(page); - return -ENOMEM; - } - io_page->p_page = page; - atomic_set(&io_page->p_count, 1); - get_page(page); set_page_writeback(page); ClearPageError(page); - for (bh = head = page_buffers(page), block_start = 0; - bh != head || !block_start; - block_start = block_end, bh = bh->b_this_page) { - - block_end = block_start + blocksize; + /* + * In the first loop we prepare and mark buffers to submit. We have to + * mark all buffers in the page before submitting so that + * end_page_writeback() cannot be called from ext4_bio_end_io() when IO + * on the first buffer finishes and we are still working on submitting + * the second buffer. + */ + bh = head = page_buffers(page); + do { + block_start = bh_offset(bh); if (block_start >= len) { /* * Comments copied from block_write_full_page_endio: @@ -431,7 +406,8 @@ int ext4_bio_write_page(struct ext4_io_submit *io, * mapped, and writes to that region are not written * out to the file." */ - zero_user_segment(page, block_start, block_end); + zero_user_segment(page, block_start, + block_start + blocksize); clear_buffer_dirty(bh); set_buffer_uptodate(bh); continue; @@ -445,7 +421,19 @@ int ext4_bio_write_page(struct ext4_io_submit *io, ext4_io_submit(io); continue; } - ret = io_submit_add_bh(io, io_page, inode, wbc, bh); + if (buffer_new(bh)) { + clear_buffer_new(bh); + unmap_underlying_metadata(bh->b_bdev, bh->b_blocknr); + } + set_buffer_async_write(bh); + } while ((bh = bh->b_this_page) != head); + + /* Now submit buffers to write */ + bh = head = page_buffers(page); + do { + if (!buffer_async_write(bh)) + continue; + ret = io_submit_add_bh(io, inode, wbc, bh); if (ret) { /* * We only get here on ENOMEM. Not much else @@ -455,17 +443,20 @@ int ext4_bio_write_page(struct ext4_io_submit *io, redirty_page_for_writepage(wbc, page); break; } + nr_submitted++; clear_buffer_dirty(bh); + } while ((bh = bh->b_this_page) != head); + + /* Error stopped previous loop? Clean up buffers... */ + if (ret) { + do { + clear_buffer_async_write(bh); + bh = bh->b_this_page; + } while (bh != head); } unlock_page(page); - /* - * If the page was truncated before we could do the writeback, - * or we had a memory allocation error while trying to write - * the first buffer head, we won't have submitted any pages for - * I/O. In that case we need to make sure we've cleared the - * PageWriteback bit from the page to prevent the system from - * wedging later on. - */ - put_io_page(io_page); + /* Nothing submitted - we have to end page writeback */ + if (!nr_submitted) + end_page_writeback(page); return ret; } -- 2.43.2