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Wong" To: "Pankaj Raghav (Samsung)" Cc: david@fromorbit.com, willy@infradead.org, chandan.babu@oracle.com, brauner@kernel.org, akpm@linux-foundation.org, yang@os.amperecomputing.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, john.g.garry@oracle.com, linux-fsdevel@vger.kernel.org, hare@suse.de, p.raghav@samsung.com, mcgrof@kernel.org, gost.dev@samsung.com, cl@os.amperecomputing.com, linux-xfs@vger.kernel.org, hch@lst.de, Zi Yan Subject: Re: [PATCH v9 06/10] iomap: fix iomap_dio_zero() for fs bs > system page size Message-ID: <20240708175632.GN612460@frogsfrogsfrogs> References: <20240704112320.82104-1-kernel@pankajraghav.com> <20240704112320.82104-7-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240704112320.82104-7-kernel@pankajraghav.com> X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 6E8ADA001D X-Stat-Signature: ipu6q3ef6b9nmc4z364cptcpeupwguxs X-Rspam-User: X-HE-Tag: 1720461394-894982 X-HE-Meta: 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 QYPD2FzA wBVnzIF3NcwmmsTcxglsGc+l8VY63zAaOXtJfNi6m1zjpCxO6RCbwYfPJ7zTMb7e/XM3EmHdPImSXRffYARAzs4FYKjo8QSSJxln6M5w0oyv25PWKcLj+F49Dt/eCpVW0LW+OHGvRv5yxgi2K3Zd0rg/Ov7HyFYJvqj4pDm10LSuuWVKnWi0Qdn6jKmBbx/r5c/r12Fdf4mquTe8N04Hsdm3cs6O96zK9dMz8vvjJ641n10eFA6Z5lVphdZ4O7v0zIvKFiKwRd5XO+SvDwK+r8DfdFkJ8lu73HFS2yJ++8KdileaLK7pq5qWQ284vxAqQiesy7puuHWF06nw+a9i+Vo8+0PTo2aJEGHfk X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Jul 04, 2024 at 11:23:16AM +0000, Pankaj Raghav (Samsung) wrote: > From: Pankaj Raghav > > iomap_dio_zero() will pad a fs block with zeroes if the direct IO size > < fs block size. iomap_dio_zero() has an implicit assumption that fs block > size < page_size. This is true for most filesystems at the moment. > > If the block size > page size, this will send the contents of the page > next to zero page(as len > PAGE_SIZE) to the underlying block device, > causing FS corruption. > > iomap is a generic infrastructure and it should not make any assumptions > about the fs block size and the page size of the system. > > Signed-off-by: Pankaj Raghav > --- > fs/iomap/buffered-io.c | 4 ++-- > fs/iomap/direct-io.c | 45 ++++++++++++++++++++++++++++++++++++------ > 2 files changed, 41 insertions(+), 8 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index f420c53d86acc..d745f718bcde8 100644 > --- a/fs/iomap/buffered-io.c > +++ b/fs/iomap/buffered-io.c > @@ -2007,10 +2007,10 @@ iomap_writepages(struct address_space *mapping, struct writeback_control *wbc, > } > EXPORT_SYMBOL_GPL(iomap_writepages); > > -static int __init iomap_init(void) > +static int __init iomap_buffered_init(void) > { > return bioset_init(&iomap_ioend_bioset, 4 * (PAGE_SIZE / SECTOR_SIZE), > offsetof(struct iomap_ioend, io_bio), > BIOSET_NEED_BVECS); > } > -fs_initcall(iomap_init); > +fs_initcall(iomap_buffered_init); > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index f3b43d223a46e..c02b266bba525 100644 > --- a/fs/iomap/direct-io.c > +++ b/fs/iomap/direct-io.c > @@ -11,6 +11,7 @@ > #include > #include > #include > +#include > #include > #include "trace.h" > > @@ -27,6 +28,13 @@ > #define IOMAP_DIO_WRITE (1U << 30) > #define IOMAP_DIO_DIRTY (1U << 31) > > +/* > + * Used for sub block zeroing in iomap_dio_zero() > + */ > +#define IOMAP_ZERO_PAGE_SIZE (SZ_64K) > +#define IOMAP_ZERO_PAGE_ORDER (get_order(IOMAP_ZERO_PAGE_SIZE)) > +static struct page *zero_page; > + > struct iomap_dio { > struct kiocb *iocb; > const struct iomap_dio_ops *dops; > @@ -232,13 +240,20 @@ void iomap_dio_bio_end_io(struct bio *bio) > } > EXPORT_SYMBOL_GPL(iomap_dio_bio_end_io); > > -static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, > +static int iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, > loff_t pos, unsigned len) > { > struct inode *inode = file_inode(dio->iocb->ki_filp); > - struct page *page = ZERO_PAGE(0); > struct bio *bio; > > + if (!len) > + return 0; > + /* > + * Max block size supported is 64k > + */ > + if (WARN_ON_ONCE(len > IOMAP_ZERO_PAGE_SIZE)) > + return -EINVAL; > + > bio = iomap_dio_alloc_bio(iter, dio, 1, REQ_OP_WRITE | REQ_SYNC | REQ_IDLE); > fscrypt_set_bio_crypt_ctx(bio, inode, pos >> inode->i_blkbits, > GFP_KERNEL); > @@ -246,8 +261,9 @@ static void iomap_dio_zero(const struct iomap_iter *iter, struct iomap_dio *dio, > bio->bi_private = dio; > bio->bi_end_io = iomap_dio_bio_end_io; > > - __bio_add_page(bio, page, len, 0); > + __bio_add_page(bio, zero_page, len, 0); > iomap_dio_submit_bio(iter, dio, bio, pos); > + return 0; > } > > /* > @@ -356,8 +372,10 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, > if (need_zeroout) { > /* zero out from the start of the block to the write offset */ > pad = pos & (fs_block_size - 1); > - if (pad) > - iomap_dio_zero(iter, dio, pos - pad, pad); > + > + ret = iomap_dio_zero(iter, dio, pos - pad, pad); > + if (ret) > + goto out; > } > > /* > @@ -431,7 +449,8 @@ static loff_t iomap_dio_bio_iter(const struct iomap_iter *iter, > /* zero out from the end of the write to the end of the block */ > pad = pos & (fs_block_size - 1); > if (pad) > - iomap_dio_zero(iter, dio, pos, fs_block_size - pad); > + ret = iomap_dio_zero(iter, dio, pos, > + fs_block_size - pad); > } > out: > /* Undo iter limitation to current extent */ > @@ -753,3 +772,17 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, > return iomap_dio_complete(dio); > } > EXPORT_SYMBOL_GPL(iomap_dio_rw); > + > +static int __init iomap_dio_init(void) > +{ > + zero_page = alloc_pages(GFP_KERNEL | __GFP_ZERO, > + IOMAP_ZERO_PAGE_ORDER); > + > + if (!zero_page) > + return -ENOMEM; > + > + set_memory_ro((unsigned long)page_address(zero_page), > + 1U << IOMAP_ZERO_PAGE_ORDER); > + return 0; > +} > +fs_initcall(iomap_dio_init); This ^^^ could be refactored into a zeropage.ko module some day as a separate patch to amortize the cost of the 64k buffer that never goes away. This patch looks ok though, so: Reviewed-by: Darrick J. Wong --D > -- > 2.44.1 > >