From patchwork Wed Sep 15 10:44:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Shiyang Ruan X-Patchwork-Id: 12495979 Received: from heian.cn.fujitsu.com (mail.cn.fujitsu.com [183.91.158.132]) by smtp.subspace.kernel.org (Postfix) with ESMTP id F059D3FC9 for ; Wed, 15 Sep 2021 10:46:35 +0000 (UTC) IronPort-Data: A9a23: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 IronPort-HdrOrdr: A9a23:KZJ+W6FYENxYQmFbpLqEjceALOsnbusQ8zAXPiFKKSC9Hfb0qynDpp4mPHzP6Qr5OktOpTnoAsDpKk80naQFgrX5Vo3PYOCJggWVEL0= X-IronPort-AV: E=Sophos;i="5.85,295,1624291200"; d="scan'208";a="114519033" Received: from unknown (HELO cn.fujitsu.com) ([10.167.33.5]) by heian.cn.fujitsu.com with ESMTP; 15 Sep 2021 18:45:33 +0800 Received: from G08CNEXMBPEKD04.g08.fujitsu.local (unknown [10.167.33.201]) by cn.fujitsu.com (Postfix) with ESMTP id 9D9274D0D9D2; Wed, 15 Sep 2021 18:45:27 +0800 (CST) Received: from G08CNEXCHPEKD09.g08.fujitsu.local (10.167.33.85) by G08CNEXMBPEKD04.g08.fujitsu.local (10.167.33.201) with Microsoft SMTP Server (TLS) id 15.0.1497.23; Wed, 15 Sep 2021 18:45:17 +0800 Received: from irides.mr.mr.mr (10.167.225.141) by G08CNEXCHPEKD09.g08.fujitsu.local (10.167.33.209) with Microsoft SMTP Server id 15.0.1497.23 via Frontend Transport; Wed, 15 Sep 2021 18:45:15 +0800 From: Shiyang Ruan To: , , CC: , , , , , , , , Subject: [PATCH v9 2/8] fsdax: Introduce dax_iomap_cow_copy() Date: Wed, 15 Sep 2021 18:44:55 +0800 Message-ID: <20210915104501.4146910-3-ruansy.fnst@fujitsu.com> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20210915104501.4146910-1-ruansy.fnst@fujitsu.com> References: <20210915104501.4146910-1-ruansy.fnst@fujitsu.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-yoursite-MailScanner-ID: 9D9274D0D9D2.A1A0E X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: ruansy.fnst@fujitsu.com X-Spam-Status: No In the case where the iomap is a write operation and iomap is not equal to srcmap after iomap_begin, we consider it is a CoW operation. In this case, the destination (iomap->addr) points to a newly allocated extent. It is needed to copy the data from srcmap to the extent. In theory, it is better to copy the head and tail ranges which is outside of the non-aligned area instead of copying the whole aligned range. But in dax page fault, it will always be an aligned range. So copy the whole range in this case. Signed-off-by: Shiyang Ruan Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong --- fs/dax.c | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++---- 1 file changed, 83 insertions(+), 5 deletions(-) diff --git a/fs/dax.c b/fs/dax.c index 8b482a58acae..dded08be54dc 100644 --- a/fs/dax.c +++ b/fs/dax.c @@ -1050,6 +1050,60 @@ static int dax_iomap_direct_access(const struct iomap *iomap, loff_t pos, return rc; } +/** + * dax_iomap_cow_copy - Copy the data from source to destination before write + * @pos: address to do copy from. + * @length: size of copy operation. + * @align_size: aligned w.r.t align_size (either PMD_SIZE or PAGE_SIZE) + * @srcmap: iomap srcmap + * @daddr: destination address to copy to. + * + * This can be called from two places. Either during DAX write fault (page + * aligned), to copy the length size data to daddr. Or, while doing normal DAX + * write operation, dax_iomap_actor() might call this to do the copy of either + * start or end unaligned address. In the latter case the rest of the copy of + * aligned ranges is taken care by dax_iomap_actor() itself. + */ +static int dax_iomap_cow_copy(loff_t pos, uint64_t length, size_t align_size, + const struct iomap *srcmap, void *daddr) +{ + loff_t head_off = pos & (align_size - 1); + size_t size = ALIGN(head_off + length, align_size); + loff_t end = pos + length; + loff_t pg_end = round_up(end, align_size); + bool copy_all = head_off == 0 && end == pg_end; + void *saddr = 0; + int ret = 0; + + ret = dax_iomap_direct_access(srcmap, pos, size, &saddr, NULL); + if (ret) + return ret; + + if (copy_all) { + ret = copy_mc_to_kernel(daddr, saddr, length); + return ret ? -EIO : 0; + } + + /* Copy the head part of the range */ + if (head_off) { + ret = copy_mc_to_kernel(daddr, saddr, head_off); + if (ret) + return -EIO; + } + + /* Copy the tail part of the range */ + if (end < pg_end) { + loff_t tail_off = head_off + length; + loff_t tail_len = pg_end - end; + + ret = copy_mc_to_kernel(daddr + tail_off, saddr + tail_off, + tail_len); + if (ret) + return -EIO; + } + return 0; +} + /* * The user has performed a load from a hole in the file. Allocating a new * page in the file would cause excessive storage usage for workloads with @@ -1175,16 +1229,18 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, struct iov_iter *iter) { const struct iomap *iomap = &iomi->iomap; + const struct iomap *srcmap = &iomi->srcmap; loff_t length = iomap_length(iomi); loff_t pos = iomi->pos; struct block_device *bdev = iomap->bdev; struct dax_device *dax_dev = iomap->dax_dev; loff_t end = pos + length, done = 0; + bool write = iov_iter_rw(iter) == WRITE; ssize_t ret = 0; size_t xfer; int id; - if (iov_iter_rw(iter) == READ) { + if (!write) { end = min(end, i_size_read(iomi->inode)); if (pos >= end) return 0; @@ -1193,7 +1249,12 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, return iov_iter_zero(min(length, end - pos), iter); } - if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED)) + /* + * In DAX mode, enforce either pure overwrites of written extents, or + * writes to unwritten extents as part of a copy-on-write operation. + */ + if (WARN_ON_ONCE(iomap->type != IOMAP_MAPPED && + !(iomap->flags & IOMAP_F_SHARED))) return -EIO; /* @@ -1232,6 +1293,14 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, break; } + if (write && + srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) { + ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap, + kaddr); + if (ret) + break; + } + map_len = PFN_PHYS(map_len); kaddr += offset; map_len -= offset; @@ -1243,7 +1312,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter *iomi, * validated via access_ok() in either vfs_read() or * vfs_write(), depending on which operation we are doing. */ - if (iov_iter_rw(iter) == WRITE) + if (write) xfer = dax_copy_from_iter(dax_dev, pgoff, kaddr, map_len, iter); else @@ -1385,6 +1454,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf, { struct address_space *mapping = vmf->vma->vm_file->f_mapping; const struct iomap *iomap = &iter->iomap; + const struct iomap *srcmap = &iter->srcmap; size_t size = pmd ? PMD_SIZE : PAGE_SIZE; loff_t pos = (loff_t)xas->xa_index << PAGE_SHIFT; bool write = vmf->flags & FAULT_FLAG_WRITE; @@ -1392,6 +1462,7 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf, unsigned long entry_flags = pmd ? DAX_PMD : 0; int err = 0; pfn_t pfn; + void *kaddr; if (!pmd && vmf->cow_page) return dax_fault_cow_page(vmf, iter); @@ -1404,18 +1475,25 @@ static vm_fault_t dax_fault_iter(struct vm_fault *vmf, return dax_pmd_load_hole(xas, vmf, iomap, entry); } - if (iomap->type != IOMAP_MAPPED) { + if (iomap->type != IOMAP_MAPPED && !(iomap->flags & IOMAP_F_SHARED)) { WARN_ON_ONCE(1); return pmd ? VM_FAULT_FALLBACK : VM_FAULT_SIGBUS; } - err = dax_iomap_direct_access(&iter->iomap, pos, size, NULL, &pfn); + err = dax_iomap_direct_access(iomap, pos, size, &kaddr, &pfn); if (err) return pmd ? VM_FAULT_FALLBACK : dax_fault_return(err); *entry = dax_insert_entry(xas, mapping, vmf, *entry, pfn, entry_flags, write && !sync); + if (write && + srcmap->addr != IOMAP_HOLE && srcmap->addr != iomap->addr) { + err = dax_iomap_cow_copy(pos, size, size, srcmap, kaddr); + if (err) + return dax_fault_return(err); + } + if (sync) return dax_fault_synchronous_pfnp(pfnp, pfn);