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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, linux-kernel@vger.kernel.org, yang@os.amperecomputing.com, 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 v8 06/10] iomap: fix iomap_dio_zero() for fs bs > system page size Message-ID: <20240701234000.GH612460@frogsfrogsfrogs> References: <20240625114420.719014-1-kernel@pankajraghav.com> <20240625114420.719014-7-kernel@pankajraghav.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240625114420.719014-7-kernel@pankajraghav.com> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: F2F1480012 X-Stat-Signature: pgd8r3awc68m6mj9gsiyyk7ztey4sx1p X-Rspam-User: X-HE-Tag: 1719877205-717079 X-HE-Meta: U2FsdGVkX18RhvcqvQdIvwSLG8Fm/GaE1FzrWnorABdnnTHfiQnfhpwlm+eq/bfX7Rihioa2MgTy2cZb1y2nrdFxPyB17XdGuF+kErnKHSNeoFDJAVEoiWNDnfykae7w+WazUlpFoR5YNqR9X6xMVd7NFFYM2UCNwuFvJYTOqZxSZKTfVHTNcNj1cwh9MPszv0D6qDi6y9AY4fbURA8/wtZAfSS07u9hRNMqsw7lcJFhOcbHd+IEI5v8DobT+ggfyDV9dMn7hIf6M7rKSQp0N3XYf9BshYR3S5IFoSOUdOgKo/Zp+ixYptUUXuQT6lY6fm9miqf0VWX5tfuhGYZ7K5bZmJr5GC5PgNrgOKfK96IpdbwNUfTW/ldKBYNavU84B1ZaY0sDLlmjvA07dLbnDddAQ4kI5A9+xtWAYZDYcCrfX0PnslLmjk2U7zT5BZJ33NIZpzw+0DGy3T+W3EN+JeTA0AcPlQWFK0vwLC7UnezzYx/9J+ulcPVW+cocc1AjEEPvU/AEsWEhGZzMnFu5mV9HKg7htWR1HxwV4ES4LxPg3WjZq1U8FtezBAGsvOh65DfasI/uTR4Hk4+SUG3bWBEeNaDME7S61YeVxu7DWG0BCJk0CBZpej4MMuqkOH+lqm6YK2v6KrjdIVZ2s/+8qP90IHFSwwi0jvh+OO+fcmnp9r9MCopEuzck4WXZY40DJiKCyG4eaKYKbMmRMEpxKuFROsx6mMrUti2Xo5uESPa8DGiQVleVO9MWv/ausc5cCVsgxCXkfkfjUWAaOAygoUxFrTgqejEda3I+8qziHFs2TMtktPRpphRr2I4EdOR9PtrfLH6VQBHPY/WyS0u0hY7nXGG+dVZuAiwEVuoXAiYOD+YmrtqmXsDVUibckAkNzfon33XEXls3T8IH5nI9TfmralN83WPRQ6p8QsMW0hwsPqUHyxORBH4e1eWasGjfUcgRq1dI2yEbIcFCDXe iw4O7KZE nTqlzoUdjF6+aGjCELAI0CGi60YPQscvvlNCBfMDF2QXwbiGLJrsRiBQjwtS5zcBTDJNbmc628Z5SKBt0IrWk6lP6nDjcMsU3EG/E/nkuA83biLVN0SxaE3m+6xC9PcOAYBfL+u5FiTVyThyFUmnMm9r1RZRJM5DVFuddk0lKFSyeVd+PszY7wkW75xNM4llBUbkiKdTOf2xVEMyFPHTVyA9QlsuACQHPq88isnasXRJPiRbxddLIyDEEQzsSkQSGV2lBmaeMbNmR4IDLMJUxQA2QSYYUrkiqozw1g9Vzl8QgT1Uqqp7aZ/GYQ1wyR9Tr+r96IuBJ4AVLf6SvVYHxZJDCgAKIu4i/OshK 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 Tue, Jun 25, 2024 at 11:44:16AM +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 > Reviewed-by: Hannes Reinecke Looks good to me, Reviewed-by: Darrick J. Wong --D > --- > fs/iomap/buffered-io.c | 4 ++-- > fs/iomap/direct-io.c | 30 ++++++++++++++++++++++++++++-- > 2 files changed, 30 insertions(+), 4 deletions(-) > > diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c > index f420c53d86ac..9a9e94c7ed1d 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_pagecache_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_pagecache_init); > diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c > index f3b43d223a46..61d09d2364f7 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 ZERO_PAGE_64K_SIZE (65536) > +#define ZERO_PAGE_64K_ORDER (get_order(ZERO_PAGE_64K_SIZE)) > +static struct page *zero_page_64k; > + > struct iomap_dio { > struct kiocb *iocb; > const struct iomap_dio_ops *dops; > @@ -236,9 +244,13 @@ static void 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; > > + /* > + * Max block size supported is 64k > + */ > + WARN_ON_ONCE(len > ZERO_PAGE_64K_SIZE); > + > 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); > @@ -246,7 +258,7 @@ 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_64k, len, 0); > iomap_dio_submit_bio(iter, dio, bio, pos); > } > > @@ -753,3 +765,17 @@ 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_64k = alloc_pages(GFP_KERNEL | __GFP_ZERO, > + ZERO_PAGE_64K_ORDER); > + > + if (!zero_page_64k) > + return -ENOMEM; > + > + set_memory_ro((unsigned long)page_address(zero_page_64k), > + 1U << ZERO_PAGE_64K_ORDER); > + return 0; > +} > +fs_initcall(iomap_dio_init); > -- > 2.44.1 > >