Darrick J. Wong
2020-Feb-26 17:04 UTC
[Ocfs2-devel] [PATCH v8 25/25] iomap: Convert from readpages to readahead
On Tue, Feb 25, 2020 at 01:48:38PM -0800, Matthew Wilcox wrote:> From: "Matthew Wilcox (Oracle)" <willy at infradead.org> > > Use the new readahead operation in iomap. Convert XFS and ZoneFS to > use it. > > Signed-off-by: Matthew Wilcox (Oracle) <willy at infradead.org> > --- > fs/iomap/buffered-io.c | 90 +++++++++++++++--------------------------- > fs/iomap/trace.h | 2 +- > fs/xfs/xfs_aops.c | 13 +++--- > fs/zonefs/super.c | 7 ++-- > include/linux/iomap.h | 3 +- > 5 files changed, 41 insertions(+), 74 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index cb3511eb152a..83438b3257de 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -214,9 +214,8 @@ iomap_read_end_io(struct bio *bio) > struct iomap_readpage_ctx { > struct page *cur_page; > bool cur_page_in_bio; > - bool is_readahead; > struct bio *bio; > - struct list_head *pages; > + struct readahead_control *rac; > }; > > static void > @@ -307,11 +306,11 @@ iomap_readpage_actor(struct inode *inode, loff_t pos, loff_t length, void *data, > if (ctx->bio) > submit_bio(ctx->bio); > > - if (ctx->is_readahead) /* same as readahead_gfp_mask */ > + if (ctx->rac) /* same as readahead_gfp_mask */ > gfp |= __GFP_NORETRY | __GFP_NOWARN; > ctx->bio = bio_alloc(gfp, min(BIO_MAX_PAGES, nr_vecs)); > ctx->bio->bi_opf = REQ_OP_READ; > - if (ctx->is_readahead) > + if (ctx->rac) > ctx->bio->bi_opf |= REQ_RAHEAD; > ctx->bio->bi_iter.bi_sector = sector; > bio_set_dev(ctx->bio, iomap->bdev); > @@ -367,36 +366,8 @@ iomap_readpage(struct page *page, const struct iomap_ops *ops) > } > EXPORT_SYMBOL_GPL(iomap_readpage); > > -static struct page * > -iomap_next_page(struct inode *inode, struct list_head *pages, loff_t pos, > - loff_t length, loff_t *done) > -{ > - while (!list_empty(pages)) { > - struct page *page = lru_to_page(pages); > - > - if (page_offset(page) >= (u64)pos + length) > - break; > - > - list_del(&page->lru); > - if (!add_to_page_cache_lru(page, inode->i_mapping, page->index, > - GFP_NOFS)) > - return page; > - > - /* > - * If we already have a page in the page cache at index we are > - * done. Upper layers don't care if it is uptodate after the > - * readpages call itself as every page gets checked again once > - * actually needed. > - */ > - *done += PAGE_SIZE; > - put_page(page); > - } > - > - return NULL; > -} > - > static loff_t > -iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length, > +iomap_readahead_actor(struct inode *inode, loff_t pos, loff_t length, > void *data, struct iomap *iomap, struct iomap *srcmap) > { > struct iomap_readpage_ctx *ctx = data; > @@ -410,10 +381,7 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length, > ctx->cur_page = NULL; > } > if (!ctx->cur_page) { > - ctx->cur_page = iomap_next_page(inode, ctx->pages, > - pos, length, &done); > - if (!ctx->cur_page) > - break; > + ctx->cur_page = readahead_page(ctx->rac); > ctx->cur_page_in_bio = false; > } > ret = iomap_readpage_actor(inode, pos + done, length - done, > @@ -423,32 +391,43 @@ iomap_readpages_actor(struct inode *inode, loff_t pos, loff_t length, > return done; > } > > -int > -iomap_readpages(struct address_space *mapping, struct list_head *pages, > - unsigned nr_pages, const struct iomap_ops *ops) > +/** > + * iomap_readahead - Attempt to read pages from a file. > + * @rac: Describes the pages to be read. > + * @ops: The operations vector for the filesystem. > + * > + * This function is for filesystems to call to implement their readahead > + * address_space operation. > + * > + * Context: The @ops callbacks may submit I/O (eg to read the addresses of > + * blocks from disc), and may wait for it. The caller may be trying to > + * access a different page, and so sleeping excessively should be avoided. > + * It may allocate memory, but should avoid costly allocations. This > + * function is called with memalloc_nofs set, so allocations will not cause > + * the filesystem to be reentered. > + */ > +void iomap_readahead(struct readahead_control *rac, const struct iomap_ops *ops) > { > + struct inode *inode = rac->mapping->host; > + loff_t pos = readahead_pos(rac); > + loff_t length = readahead_length(rac); > struct iomap_readpage_ctx ctx = { > - .pages = pages, > - .is_readahead = true, > + .rac = rac, > }; > - loff_t pos = page_offset(list_entry(pages->prev, struct page, lru)); > - loff_t last = page_offset(list_entry(pages->next, struct page, lru)); > - loff_t length = last - pos + PAGE_SIZE, ret = 0; > > - trace_iomap_readpages(mapping->host, nr_pages); > + trace_iomap_readahead(inode, readahead_count(rac)); > > while (length > 0) { > - ret = iomap_apply(mapping->host, pos, length, 0, ops, > - &ctx, iomap_readpages_actor); > + loff_t ret = iomap_apply(inode, pos, length, 0, ops, > + &ctx, iomap_readahead_actor); > if (ret <= 0) { > WARN_ON_ONCE(ret == 0); > - goto done; > + break; > } > pos += ret; > length -= ret; > } > - ret = 0; > -done: > + > if (ctx.bio) > submit_bio(ctx.bio); > if (ctx.cur_page) { > @@ -456,15 +435,8 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages, > unlock_page(ctx.cur_page); > put_page(ctx.cur_page); > } > - > - /* > - * Check that we didn't lose a page due to the arcance calling > - * conventions.. > - */ > - WARN_ON_ONCE(!ret && !list_empty(ctx.pages)); > - return ret;After all the discussion about "if we still have ctx.cur_page we should just stop" in v7, I'm surprised that this patch now doesn't say much of anything, not even a WARN_ON()? Other than that, it looks fine. --D> } > -EXPORT_SYMBOL_GPL(iomap_readpages); > +EXPORT_SYMBOL_GPL(iomap_readahead); > > /* > * iomap_is_partially_uptodate checks whether blocks within a page are > diff --git a/fs/iomap/trace.h b/fs/iomap/trace.h > index 6dc227b8c47e..d6ba705f938a 100644 > --- a/fs/iomap/trace.h > +++ b/fs/iomap/trace.h > @@ -39,7 +39,7 @@ DEFINE_EVENT(iomap_readpage_class, name, \ > TP_PROTO(struct inode *inode, int nr_pages), \ > TP_ARGS(inode, nr_pages)) > DEFINE_READPAGE_EVENT(iomap_readpage); > -DEFINE_READPAGE_EVENT(iomap_readpages); > +DEFINE_READPAGE_EVENT(iomap_readahead); > > DECLARE_EVENT_CLASS(iomap_page_class, > TP_PROTO(struct inode *inode, struct page *page, unsigned long off, > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index 58e937be24ce..6e68eeb50b07 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c > @@ -621,14 +621,11 @@ xfs_vm_readpage( > return iomap_readpage(page, &xfs_read_iomap_ops); > } > > -STATIC int > -xfs_vm_readpages( > - struct file *unused, > - struct address_space *mapping, > - struct list_head *pages, > - unsigned nr_pages) > +STATIC void > +xfs_vm_readahead( > + struct readahead_control *rac) > { > - return iomap_readpages(mapping, pages, nr_pages, &xfs_read_iomap_ops); > + iomap_readahead(rac, &xfs_read_iomap_ops); > } > > static int > @@ -644,7 +641,7 @@ xfs_iomap_swapfile_activate( > > const struct address_space_operations xfs_address_space_operations = { > .readpage = xfs_vm_readpage, > - .readpages = xfs_vm_readpages, > + .readahead = xfs_vm_readahead, > .writepage = xfs_vm_writepage, > .writepages = xfs_vm_writepages, > .set_page_dirty = iomap_set_page_dirty, > diff --git a/fs/zonefs/super.c b/fs/zonefs/super.c > index 8bc6ef82d693..8327a01d3bac 100644 > --- a/fs/zonefs/super.c > +++ b/fs/zonefs/super.c > @@ -78,10 +78,9 @@ static int zonefs_readpage(struct file *unused, struct page *page) > return iomap_readpage(page, &zonefs_iomap_ops); > } > > -static int zonefs_readpages(struct file *unused, struct address_space *mapping, > - struct list_head *pages, unsigned int nr_pages) > +static void zonefs_readahead(struct readahead_control *rac) > { > - return iomap_readpages(mapping, pages, nr_pages, &zonefs_iomap_ops); > + iomap_readahead(rac, &zonefs_iomap_ops); > } > > /* > @@ -128,7 +127,7 @@ static int zonefs_writepages(struct address_space *mapping, > > static const struct address_space_operations zonefs_file_aops = { > .readpage = zonefs_readpage, > - .readpages = zonefs_readpages, > + .readahead = zonefs_readahead, > .writepage = zonefs_writepage, > .writepages = zonefs_writepages, > .set_page_dirty = iomap_set_page_dirty, > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index 8b09463dae0d..bc20bd04c2a2 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -155,8 +155,7 @@ loff_t iomap_apply(struct inode *inode, loff_t pos, loff_t length, > ssize_t iomap_file_buffered_write(struct kiocb *iocb, struct iov_iter *from, > const struct iomap_ops *ops); > int iomap_readpage(struct page *page, const struct iomap_ops *ops); > -int iomap_readpages(struct address_space *mapping, struct list_head *pages, > - unsigned nr_pages, const struct iomap_ops *ops); > +void iomap_readahead(struct readahead_control *, const struct iomap_ops *ops); > int iomap_set_page_dirty(struct page *page); > int iomap_is_partially_uptodate(struct page *page, unsigned long from, > unsigned long count); > -- > 2.25.0 >
Christoph Hellwig
2020-Feb-26 17:07 UTC
[Ocfs2-devel] [PATCH v8 25/25] iomap: Convert from readpages to readahead
On Wed, Feb 26, 2020 at 09:04:25AM -0800, Darrick J. Wong wrote:> > @@ -456,15 +435,8 @@ iomap_readpages(struct address_space *mapping, struct list_head *pages, > > unlock_page(ctx.cur_page); > > put_page(ctx.cur_page); > > } > > - > > - /* > > - * Check that we didn't lose a page due to the arcance calling > > - * conventions.. > > - */ > > - WARN_ON_ONCE(!ret && !list_empty(ctx.pages)); > > - return ret; > > After all the discussion about "if we still have ctx.cur_page we should > just stop" in v7, I'm surprised that this patch now doesn't say much of > anything, not even a WARN_ON()?The code quoted above puts the cur_page reference. By dropping the odd refactoring patch there is no need to check for cur_page being left as a special condition as that still is the normal loop exit state and properly handled, just as in the original iomap code.