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Wong" Date: Sat, 24 Jul 2021 21:34:42 +0200 Message-Id: <20210724193449.361667-2-agruenba@redhat.com> In-Reply-To: <20210724193449.361667-1-agruenba@redhat.com> References: <20210724193449.361667-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 ip4:103.23.64.2 ip4:103.23.65.2 ip4:103.23.66.26 ip4:103.23.67.26 ip4:107.21.15.141 ip4:108.177.8.0/21 ip4:128.17.0.0/20 ip4:128.17.128.0/20 ip4:128.17.192.0/20 ip4:128.17.64.0/20 ip4:128.245.0.0/20 ip4:128.245.64.0/20 ip4:13.110.208.0/21 ip4:13.111.0.0/16 ip4:136.147.128.0/20 ip4:136.147.176.0/20 ip4:148.105.8.0/21 ip4:148.139.0.2 include:spf1.redhat.com -all X-Proofpoint-SPF-VenPass: Allowed X-Source-IP: 170.10.133.124 X-ServerName: us-smtp-delivery-124.mimecast.com X-Proofpoint-SPF-Result: pass X-Proofpoint-SPF-Record: v=spf1 ip4:103.23.64.2 ip4:103.23.65.2 ip4:103.23.66.26 ip4:103.23.67.26 ip4:107.21.15.141 ip4:108.177.8.0/21 ip4:128.17.0.0/20 ip4:128.17.128.0/20 ip4:128.17.192.0/20 ip4:128.17.64.0/20 ip4:128.245.0.0/20 ip4:128.245.64.0/20 ip4:13.110.208.0/21 ip4:13.111.0.0/16 ip4:136.147.128.0/20 ip4:136.147.176.0/20 ip4:148.105.8.0/21 ip4:148.139.0.2 include:spf1.redhat.com -all X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Reason: safe X-Spam: OrgSafeList X-SpamRule: orgsafelist X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxlogscore=999 phishscore=0 suspectscore=0 adultscore=0 mlxscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240117 Cc: Jan Kara , Andreas Gruenbacher , linux-kernel@vger.kernel.org, cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org, ocfs2-devel@oss.oracle.com Subject: [Ocfs2-devel] [PATCH v4 1/8] iov_iter: Introduce iov_iter_fault_in_writeable helper X-BeenThere: ocfs2-devel@oss.oracle.com X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: ocfs2-devel-bounces@oss.oracle.com Errors-To: ocfs2-devel-bounces@oss.oracle.com X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10055 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 bulkscore=0 phishscore=0 malwarescore=0 spamscore=0 mlxlogscore=999 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107240117 X-Proofpoint-GUID: ERp47Xt53DKiqVpkMT-sLFHttxgVPo4C X-Proofpoint-ORIG-GUID: ERp47Xt53DKiqVpkMT-sLFHttxgVPo4C Introduce a new iov_iter_fault_in_writeable helper for faulting in an iterator for writing. The pages are faulted in manually, without writing to them, so this function is non-destructive. We'll use iov_iter_fault_in_writeable in gfs2 once we've determined that part of the iterator isn't in memory. Signed-off-by: Andreas Gruenbacher --- include/linux/mm.h | 3 +++ include/linux/uio.h | 1 + lib/iov_iter.c | 40 +++++++++++++++++++++++++++++++ mm/gup.c | 57 +++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 101 insertions(+) diff --git a/include/linux/mm.h b/include/linux/mm.h index 7ca22e6e694a..14b1353995e2 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1840,6 +1840,9 @@ int get_user_pages_fast(unsigned long start, int nr_pages, int pin_user_pages_fast(unsigned long start, int nr_pages, unsigned int gup_flags, struct page **pages); +unsigned long fault_in_user_pages(unsigned long start, unsigned long len, + bool write); + int account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc); int __account_locked_vm(struct mm_struct *mm, unsigned long pages, bool inc, struct task_struct *task, bool bypass_rlim); diff --git a/include/linux/uio.h b/include/linux/uio.h index 82c3c3e819e0..8e469b8b862f 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -120,6 +120,7 @@ size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, void iov_iter_advance(struct iov_iter *i, size_t bytes); void iov_iter_revert(struct iov_iter *i, size_t bytes); int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes); +int iov_iter_fault_in_writeable(const struct iov_iter *i, size_t bytes); size_t iov_iter_single_seg_count(const struct iov_iter *i); size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i); diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 20dc3d800573..ccf1ee8d4edf 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -460,6 +460,46 @@ int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes) } EXPORT_SYMBOL(iov_iter_fault_in_readable); +/** + * iov_iter_fault_in_writeable - fault in an iov iterator for writing + * @i: iterator + * @bytes: maximum length + * + * Faults in part or all of the iterator. This is primarily useful when we + * already know that some or all of the pages in @i aren't in memory. + * + * This function uses fault_in_user_pages() to fault in the pages, which + * internally uses get_user_pages(), so it doesn't trigger hardware page + * faults. Unlike fault_in_pages_writeable() which writes to the memory to + * fault it in, this function is non-destructive. + * + * Returns 0 on success, and a non-zero error code if the memory could not be + * accessed (i.e. because it is an invalid address). + */ +int iov_iter_fault_in_writeable(const struct iov_iter *i, size_t bytes) +{ + if (iter_is_iovec(i)) { + const struct iovec *p; + size_t skip; + + if (bytes > i->count) + bytes = i->count; + for (p = i->iov, skip = i->iov_offset; bytes; p++, skip = 0) { + unsigned long len = min(bytes, p->iov_len - skip); + unsigned long start; + + if (unlikely(!len)) + continue; + start = (unsigned long)p->iov_base + skip; + if (fault_in_user_pages(start, len, true) != len) + return -EFAULT; + bytes -= len; + } + } + return 0; +} +EXPORT_SYMBOL(iov_iter_fault_in_writeable); + void iov_iter_init(struct iov_iter *i, unsigned int direction, const struct iovec *iov, unsigned long nr_segs, size_t count) diff --git a/mm/gup.c b/mm/gup.c index 42b8b1fa6521..784809c232f1 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1669,6 +1669,63 @@ static long __get_user_pages_locked(struct mm_struct *mm, unsigned long start, } #endif /* !CONFIG_MMU */ +/** + * fault_in_user_pages - fault in an address range for reading / writing + * @start: start of address range + * @len: length of address range + * @write: fault in for writing + * + * Note that we don't pin or otherwise hold the pages referenced that we fault + * in. There's no guarantee that they'll stay in memory for any duration of + * time. + * + * Returns the number of bytes faulted in from @start. + */ +unsigned long fault_in_user_pages(unsigned long start, unsigned long len, + bool write) +{ + struct mm_struct *mm = current->mm; + struct vm_area_struct *vma = NULL; + unsigned long end, nstart, nend; + int locked = 0; + int gup_flags; + + gup_flags = FOLL_TOUCH | FOLL_POPULATE; + if (write) + gup_flags |= FOLL_WRITE; + + end = PAGE_ALIGN(start + len); + for (nstart = start & PAGE_MASK; nstart < end; nstart = nend) { + unsigned long nr_pages; + long ret; + + if (!locked) { + locked = 1; + mmap_read_lock(mm); + vma = find_vma(mm, nstart); + } else if (nstart >= vma->vm_end) + vma = vma->vm_next; + if (!vma || vma->vm_start >= end) + break; + nend = min(end, vma->vm_end); + if (vma->vm_flags & (VM_IO | VM_PFNMAP)) + continue; + if (nstart < vma->vm_start) + nstart = vma->vm_start; + nr_pages = (nend - nstart) / PAGE_SIZE; + ret = __get_user_pages_locked(mm, nstart, nr_pages, + NULL, NULL, &locked, gup_flags); + if (ret <= 0) + break; + nend = nstart + ret * PAGE_SIZE; + } + if (locked) + mmap_read_unlock(mm); + if (nstart > start) + return min(nstart - start, len); + return 0; +} + /** * get_dump_page() - pin user page in memory while writing it to core dump * @addr: user address -- 2.26.3 _______________________________________________ Ocfs2-devel mailing list Ocfs2-devel@oss.oracle.com https://oss.oracle.com/mailman/listinfo/ocfs2-devel