From: =?UTF-8?Q?Andreas_Gr=C3=BCnbacher?= Subject: Re: [PATCH 4/6] vfs: Add iomap_seek_hole and iomap_seek_data helpers Date: Wed, 28 Jun 2017 00:14:57 +0200 Message-ID: References: <20170627214828.1029-1-hch@lst.de> <20170627214828.1029-5-hch@lst.de> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Cc: Andreas Gruenbacher , Jan Kara , Linux FS-devel Mailing List , linux-xfs@vger.kernel.org, linux-ext4@vger.kernel.org To: Christoph Hellwig Return-path: Received: from mail-yb0-f196.google.com ([209.85.213.196]:35738 "EHLO mail-yb0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753883AbdF0WO6 (ORCPT ); Tue, 27 Jun 2017 18:14:58 -0400 In-Reply-To: <20170627214828.1029-5-hch@lst.de> Sender: linux-ext4-owner@vger.kernel.org List-ID: 2017-06-27 23:48 GMT+02:00 Christoph Hellwig : > From: Andreas Gruenbacher > > Filesystems can use this for implementing lseek SEEK_HOLE / SEEK_DATA > support via iomap. > > Signed-off-by: Andreas Gruenbacher > [hch: split functions, coding style cleanups] > Signed-off-by: Christoph Hellwig > --- > fs/iomap.c | 98 +++++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/iomap.h | 4 +++ > 2 files changed, 102 insertions(+) > > diff --git a/fs/iomap.c b/fs/iomap.c > index 4b10892967a5..c90cda33994b 100644 > --- a/fs/iomap.c > +++ b/fs/iomap.c > @@ -584,6 +584,104 @@ int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fi, > } > EXPORT_SYMBOL_GPL(iomap_fiemap); > > +static loff_t > +iomap_seek_hole_actor(struct inode *inode, loff_t offset, loff_t length, > + void *data, struct iomap *iomap) > +{ > + switch (iomap->type) { > + case IOMAP_UNWRITTEN: > + offset = page_cache_seek_hole_data(inode, offset, length, > + SEEK_HOLE); > + if (offset < 0) > + return length; > + /* fall through */ > + case IOMAP_HOLE: > + *(loff_t *)data = offset; > + return 0; > + default: > + return length; > + } > +} > + > +loff_t > +iomap_seek_hole(struct inode *inode, loff_t offset, const struct iomap_ops *ops) > +{ > + loff_t size = i_size_read(inode); > + loff_t length = size - offset; > + loff_t ret; > + > + /* Nothing to be found beyond the end of the file. */ > + if (offset >= size) > + return -ENXIO; > + > + while (length > 0) { > + ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, > + &offset, iomap_seek_hole_actor); > + if (ret < 0) > + return ret; > + if (ret == 0) > + break; > + > + offset += ret; > + length -= ret; > + } > + > + /* The last segment can extend beyond the end of the file. */ > + if (length <= 0) > + return min(offset, size); This shouldn't be true anymore now that the actors don't recompute the length; the above three lines should be obsolete. > + return offset; > +} > +EXPORT_SYMBOL_GPL(iomap_seek_hole); > + > +static loff_t > +iomap_seek_data_actor(struct inode *inode, loff_t offset, loff_t length, > + void *data, struct iomap *iomap) > +{ > + switch (iomap->type) { > + case IOMAP_HOLE: > + return length; > + case IOMAP_UNWRITTEN: > + offset = page_cache_seek_hole_data(inode, offset, length, > + SEEK_DATA); > + if (offset < 0) > + return length; > + /*FALLTHRU*/ > + default: > + *(loff_t *)data = offset; > + return 0; > + } > +} > + > +loff_t > +iomap_seek_data(struct inode *inode, loff_t offset, const struct iomap_ops *ops) > +{ > + loff_t size = i_size_read(inode); > + loff_t length = size - offset; > + loff_t ret; > + > + /* Nothing to be found beyond the end of the file. */ > + if (offset >= size) > + return -ENXIO; > + > + while (length > 0) { > + ret = iomap_apply(inode, offset, length, IOMAP_REPORT, ops, > + &offset, iomap_seek_data_actor); > + if (ret < 0) > + return ret; > + if (ret == 0) > + break; > + > + offset += ret; > + length -= ret; > + } > + > + /* There is an implicit hole at the end of the file. */ This comment makes more sense in iomap_seek_hole now. > + if (length <= 0) > + return -ENXIO; > + return offset; > +} > +EXPORT_SYMBOL_GPL(iomap_seek_data); > + > /* > * Private flags for iomap_dio, must not overlap with the public ones in > * iomap.h: > diff --git a/include/linux/iomap.h b/include/linux/iomap.h > index f753e788da31..8a03f5dcd89b 100644 > --- a/include/linux/iomap.h > +++ b/include/linux/iomap.h > @@ -83,6 +83,10 @@ int iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero, > int iomap_page_mkwrite(struct vm_fault *vmf, const struct iomap_ops *ops); > int iomap_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, > loff_t start, loff_t len, const struct iomap_ops *ops); > +loff_t iomap_seek_hole(struct inode *inode, loff_t offset, > + const struct iomap_ops *ops); > +loff_t iomap_seek_data(struct inode *inode, loff_t offset, > + const struct iomap_ops *ops); > > /* > * Flags for direct I/O ->end_io: > -- > 2.11.0 Thanks, Andreas