On 2018/8/13 19:04, Dan Carpenter wrote: > On Sun, Aug 12, 2018 at 10:01:44PM +0800, Chao Yu wrote: >> --- a/drivers/staging/erofs/data.c >> +++ b/drivers/staging/erofs/data.c >> @@ -39,31 +39,44 @@ static inline void read_endio(struct bio *bio) >> } >> >> /* prio -- true is used for dir */ >> -struct page *erofs_get_meta_page(struct super_block *sb, >> - erofs_blk_t blkaddr, bool prio) >> +struct page *__erofs_get_meta_page(struct super_block *sb, >> + erofs_blk_t blkaddr, bool prio, bool nofail) >> { >> - struct inode *bd_inode = sb->s_bdev->bd_inode; >> - struct address_space *mapping = bd_inode->i_mapping; >> + struct inode *const bd_inode = sb->s_bdev->bd_inode; >> + struct address_space *const mapping = bd_inode->i_mapping; >> + /* prefer retrying in the allocator to blindly looping below */ >> + const gfp_t gfp = mapping_gfp_constraint(mapping, ~__GFP_FS) | >> + (nofail ? __GFP_NOFAIL : 0); >> + unsigned int io_retries = nofail ? EROFS_IO_MAX_RETRIES_NOFAIL : 0; >> struct page *page; >> >> repeat: >> - page = find_or_create_page(mapping, blkaddr, >> - /* >> - * Prefer looping in the allocator rather than here, >> - * at least that code knows what it's doing. >> - */ >> - mapping_gfp_constraint(mapping, ~__GFP_FS) | __GFP_NOFAIL); >> - >> - BUG_ON(!page || !PageLocked(page)); >> + page = find_or_create_page(mapping, blkaddr, gfp); >> + if (unlikely(page == NULL)) { >> + DBG_BUGON(nofail); >> + return ERR_PTR(-ENOMEM); >> + } >> + DBG_BUGON(!PageLocked(page)); >> >> if (!PageUptodate(page)) { >> struct bio *bio; >> int err; >> >> - bio = erofs_grab_bio(sb, blkaddr, 1, read_endio, true); >> + bio = erofs_grab_bio(sb, blkaddr, 1, read_endio, nofail); >> + if (unlikely(bio == NULL)) { >> + DBG_BUGON(nofail); >> + err = -ENOMEM; >> +err_out: >> + unlock_page(page); >> + put_page(page); >> + return ERR_PTR(err); > > > Put this err_out stuff at the bottom of the function so that we don't > have to do backward hops to get to it.
Agreed, we can move error path at the bottom of this function. > >> + } >> >> err = bio_add_page(bio, page, PAGE_SIZE, 0); >> - BUG_ON(err != PAGE_SIZE); >> + if (unlikely(err != PAGE_SIZE)) { >> + err = -EFAULT; >> + goto err_out; > ^^^^^^^^^^^^ > Like this. Generally avoid backwards hops if you can. > >> + } >> >> __submit_bio(bio, REQ_OP_READ, >> REQ_META | (prio ? REQ_PRIO : 0)); >> @@ -72,6 +85,7 @@ struct page *erofs_get_meta_page(struct super_block *sb, >> >> /* the page has been truncated by others? */ >> if (unlikely(page->mapping != mapping)) { >> +unlock_repeat: > > The question mark in the "truncated by others?" is a little concerning. Yup, we can remove the question mark. > It's slightly weird that we don't check "io_retries" on this path. We don't need to cover this path since io_retries is used for accounting retry time only when IO occurs. Thanks, > >> unlock_page(page); >> put_page(page); >> goto repeat; >> @@ -79,10 +93,12 @@ struct page *erofs_get_meta_page(struct super_block *sb, >> >> /* more likely a read error */ >> if (unlikely(!PageUptodate(page))) { >> - unlock_page(page); >> - put_page(page); >> - >> - page = ERR_PTR(-EIO); >> + if (io_retries) { >> + --io_retries; >> + goto unlock_repeat; >> + } >> + err = -EIO; >> + goto err_out; > > regards, > dan carpenter >