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Wong" Date: Fri, 23 Jul 2021 22:58:34 +0200 Message-Id: <20210723205840.299280-2-agruenba@redhat.com> In-Reply-To: <20210723205840.299280-1-agruenba@redhat.com> References: <20210723205840.299280-1-agruenba@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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: 216.205.24.124 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=10054 signatures=668682 X-Proofpoint-Spam-Reason: safe X-Spam: OrgSafeList X-SpamRule: orgsafelist X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=10054 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 spamscore=0 mlxscore=0 malwarescore=0 adultscore=0 phishscore=0 suspectscore=0 mlxlogscore=999 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107230126 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 v3 1/7] iov_iter: Introduce fault_in_iov_iter 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=10054 signatures=668682 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 malwarescore=0 mlxscore=0 mlxlogscore=999 adultscore=0 bulkscore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104190000 definitions=main-2107230126 X-Proofpoint-ORIG-GUID: HO9c6D6ypT-zDQNts1W61rLD4KLQqVte X-Proofpoint-GUID: HO9c6D6ypT-zDQNts1W61rLD4KLQqVte Introduce a new fault_in_iov_iter helper for manually faulting in an iterator. Other than fault_in_pages_writeable(), this function is non-destructive. We'll use fault_in_iov_iter in gfs2 once we've determined that the iterator passed to .read_iter or .write_iter isn't in memory. Signed-off-by: Andreas Gruenbacher --- include/linux/mm.h | 3 ++ include/linux/uio.h | 1 + lib/iov_iter.c | 42 ++++++++++++++++++++++++++++ mm/gup.c | 68 +++++++++++++++++++++++++++++++++++++++++++++ 4 files changed, 114 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..152b3605e86c 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); +size_t fault_in_iov_iter(const struct iov_iter *i); 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..7221665f7ac4 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -460,6 +460,48 @@ int iov_iter_fault_in_readable(const struct iov_iter *i, size_t bytes) } EXPORT_SYMBOL(iov_iter_fault_in_readable); +/** + * fault_in_iov_iter - fault in iov iterator for reading / writing + * @i: iterator + * + * Faults in the iterator using get_user_pages, i.e., without triggering + * hardware page faults. + * + * This is primarily useful when we know that some or all of the pages in @i + * aren't in memory. For iterators that are likely to be in memory, + * fault_in_pages_readable() may be more appropriate. + * + * Other than fault_in_pages_writeable(), this function is non-destructive even + * when faulting in pages for writing. + * + * Returns the number of bytes faulted in, or the size of @i if @i doesn't need + * faulting in. + */ +size_t fault_in_iov_iter(const struct iov_iter *i) +{ + size_t count = i->count; + const struct iovec *p; + size_t ret = 0, skip; + + if (iter_is_iovec(i)) { + for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) { + unsigned long len = min(count, p->iov_len - skip); + unsigned long start, l; + + if (unlikely(!len)) + continue; + start = (unsigned long)p->iov_base + skip; + l = fault_in_user_pages(start, len, iov_iter_rw(i) != WRITE); + ret += l; + if (unlikely(l != len)) + break; + count -= l; + } + } + return ret; +} +EXPORT_SYMBOL(fault_in_iov_iter); + 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..033d66586c62 100644 --- a/mm/gup.c +++ b/mm/gup.c @@ -1669,6 +1669,74 @@ 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; + + /* + * FIXME: Make sure this function doesn't succeed for pages that cannot + * be accessed; otherwise we could end up in a loop trying to fault in + * and then access the pages. (It's okay if a page gets evicted and we + * need more than one retry.) + */ + + /* + * FIXME: Are these the right FOLL_* 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