From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 9 May 2018 17:20:02 +0200 From: Jan Kara To: "Darrick J. Wong" Cc: xfs , linux-fsdevel , linux-mm@kvack.org, hch@infradead.org, cyberax@amazon.com, jack@suse.cz, osandov@osandov.com, Eryu Guan Subject: Re: [PATCH v3 1/2] iomap: add a swapfile activation function Message-ID: <20180509152002.kuqjfpyzlxdc7izg@quack2.suse.cz> References: <20180503174659.GD4127@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180503174659.GD4127@magnolia> Sender: owner-linux-mm@kvack.org List-ID: On Thu 03-05-18 10:46:59, Darrick J. Wong wrote: > From: Darrick J. Wong > > Add a new iomap_swapfile_activate function so that filesystems can > activate swap files without having to use the obsolete and slow bmap > function. This enables XFS to support fallocate'd swap files and > swap files on realtime devices. > > Signed-off-by: Darrick J. Wong > --- > v3: catch null iomap addr, fix too-short extent detection > v2: document the swap file layout requirements, combine adjacent > real/unwritten extents, align reported swap extents to physical page > size boundaries, fix compiler errors when swap disabled > --- > fs/iomap.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++ > fs/xfs/xfs_aops.c | 12 ++++ > include/linux/iomap.h | 11 +++ > 3 files changed, 185 insertions(+) > > diff --git a/fs/iomap.c b/fs/iomap.c > index afd163586aa0..ac7115492366 100644 > --- a/fs/iomap.c > +++ b/fs/iomap.c > @@ -27,6 +27,7 @@ > #include > #include > #include > +#include > > #include "internal.h" > > @@ -1089,3 +1090,164 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > return ret; > } > EXPORT_SYMBOL_GPL(iomap_dio_rw); > + > +/* Swapfile activation */ > + > +#ifdef CONFIG_SWAP > +struct iomap_swapfile_info { > + struct iomap iomap; /* accumulated iomap */ > + struct swap_info_struct *sis; > + uint64_t lowest_ppage; /* lowest physical addr seen (pages) */ > + uint64_t highest_ppage; /* highest physical addr seen (pages) */ > + unsigned long nr_pages; /* number of pages collected */ > + int nr_extents; /* extent count */ > +}; > + > +/* > + * Collect physical extents for this swap file. Physical extents reported to > + * the swap code must be trimmed to align to a page boundary. The logical > + * offset within the file is irrelevant since the swapfile code maps logical > + * page numbers of the swap device to the physical page-aligned extents. > + */ > +static int iomap_swapfile_add_extent(struct iomap_swapfile_info *isi) > +{ > + struct iomap *iomap = &isi->iomap; > + unsigned long nr_pages; > + uint64_t first_ppage; > + uint64_t first_ppage_reported; > + uint64_t last_ppage; > + int error; > + > + /* > + * Round the start up and the end down so that the physical > + * extent aligns to a page boundary. > + */ > + first_ppage = ALIGN(iomap->addr, PAGE_SIZE) >> PAGE_SHIFT; > + last_ppage = (ALIGN_DOWN(iomap->addr + iomap->length, PAGE_SIZE) >> > + PAGE_SHIFT) - 1; But this can still end up underflowing last_ppage to (unsigned long)-1 and the following test won't trigger? > + > + /* Skip too-short physical extents. */ > + if (first_ppage > last_ppage) > + return 0; Honza -- Jan Kara SUSE Labs, CR