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[83.9.1.117]) by smtp.gmail.com with ESMTPSA id h2-20020a056402094200b004acb42134c4sm7001477edz.70.2023.02.15.04.00.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 15 Feb 2023 04:00:44 -0800 (PST) From: Konrad Dybcio Date: Wed, 15 Feb 2023 13:00:39 +0100 Subject: [PATCH 2/2] Revert "splice: Do splice read from a buffered file without using ITER_PIPE" MIME-Version: 1.0 Message-Id: <20230215-topic-next-20230214-revert-v1-2-c58cd87b9086@linaro.org> References: <20230215-topic-next-20230214-revert-v1-0-c58cd87b9086@linaro.org> In-Reply-To: <20230215-topic-next-20230214-revert-v1-0-c58cd87b9086@linaro.org> To: Alexander Viro , Steve French , Paulo Alcantara , Ronnie Sahlberg , Shyam Prasad N , Tom Talpey , "Matthew Wilcox (Oracle)" , Andrew Morton Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-cifs@vger.kernel.org, samba-technical@lists.samba.org, linux-mm@kvack.org, Konrad Dybcio X-Mailer: b4 0.12.1 X-Developer-Signature: v=1; a=ed25519-sha256; t=1676462440; l=5678; i=konrad.dybcio@linaro.org; s=20230215; h=from:subject:message-id; bh=GhZqoVotGOrdGVVTlpDSlth0cBTnSieaqw2vZSOgwMg=; b=kNOAlZxm146sX4RVEP1agu2t6Duxj4iwCjq2UwEUESRutNpNxNhcL8oQbqfeiw57PyJEeXzT37Oe coVqbCJODCzECjLMISdgy6cJo3Khk2+tqwAcR/SUcXvaAedyrvLB X-Developer-Key: i=konrad.dybcio@linaro.org; a=ed25519; pk=iclgkYvtl2w05SSXO5EjjSYlhFKsJ+5OSZBjOkQuEms= X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org next-20230213 introduced commit d9722a475711 ("splice: Do splice read from a buffered file without using ITER_PIPE") which broke booting on any Qualcomm ARM64 device I grabbed, dereferencing a null pointer in generic_filesplice_read+0xf8/x598. Revert it to make the devices bootable again. This reverts commit d9722a47571104f7fa1eeb5ec59044d3607c6070. Signed-off-by: Konrad Dybcio --- fs/splice.c | 159 +++++++++--------------------------------------------------- 1 file changed, 24 insertions(+), 135 deletions(-) diff --git a/fs/splice.c b/fs/splice.c index fa82dfee1ed0..10b258250868 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -22,7 +22,6 @@ #include #include #include -#include #include #include #include @@ -378,135 +377,6 @@ static ssize_t generic_file_direct_splice_read(struct file *in, loff_t *ppos, return ret; } -/* - * Splice subpages from a folio into a pipe. - */ -static size_t splice_folio_into_pipe(struct pipe_inode_info *pipe, - struct folio *folio, - loff_t fpos, size_t size) -{ - struct page *page; - size_t spliced = 0, offset = offset_in_folio(folio, fpos); - - page = folio_page(folio, offset / PAGE_SIZE); - size = min(size, folio_size(folio) - offset); - offset %= PAGE_SIZE; - - while (spliced < size && - !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) { - struct pipe_buffer *buf = &pipe->bufs[pipe->head & (pipe->ring_size - 1)]; - size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced); - - *buf = (struct pipe_buffer) { - .ops = &page_cache_pipe_buf_ops, - .page = page, - .offset = offset, - .len = part, - }; - folio_get(folio); - pipe->head++; - page++; - spliced += part; - offset = 0; - } - - return spliced; -} - -/* - * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into - * a pipe. - */ -static ssize_t generic_file_buffered_splice_read(struct file *in, loff_t *ppos, - struct pipe_inode_info *pipe, - size_t len, - unsigned int flags) -{ - struct folio_batch fbatch; - size_t total_spliced = 0, used, npages; - loff_t isize, end_offset; - bool writably_mapped; - int i, error = 0; - - struct kiocb iocb = { - .ki_filp = in, - .ki_pos = *ppos, - }; - - /* Work out how much data we can actually add into the pipe */ - used = pipe_occupancy(pipe->head, pipe->tail); - npages = max_t(ssize_t, pipe->max_usage - used, 0); - len = min_t(size_t, len, npages * PAGE_SIZE); - - folio_batch_init(&fbatch); - - do { - cond_resched(); - - if (*ppos >= i_size_read(file_inode(in))) - break; - - iocb.ki_pos = *ppos; - error = filemap_get_pages(&iocb, len, &fbatch, true); - if (error < 0) - break; - - /* - * i_size must be checked after we know the pages are Uptodate. - * - * Checking i_size after the check allows us to calculate - * the correct value for "nr", which means the zero-filled - * part of the page is not copied back to userspace (unless - * another truncate extends the file - this is desired though). - */ - isize = i_size_read(file_inode(in)); - if (unlikely(*ppos >= isize)) - break; - end_offset = min_t(loff_t, isize, *ppos + len); - - /* - * Once we start copying data, we don't want to be touching any - * cachelines that might be contended: - */ - writably_mapped = mapping_writably_mapped(in->f_mapping); - - for (i = 0; i < folio_batch_count(&fbatch); i++) { - struct folio *folio = fbatch.folios[i]; - size_t n; - - if (folio_pos(folio) >= end_offset) - goto out; - folio_mark_accessed(folio); - - /* - * If users can be writing to this folio using arbitrary - * virtual addresses, take care of potential aliasing - * before reading the folio on the kernel side. - */ - if (writably_mapped) - flush_dcache_folio(folio); - - n = splice_folio_into_pipe(pipe, folio, *ppos, len); - if (!n) - goto out; - len -= n; - total_spliced += n; - *ppos += n; - in->f_ra.prev_pos = *ppos; - if (pipe_full(pipe->head, pipe->tail, pipe->max_usage)) - goto out; - } - - folio_batch_release(&fbatch); - } while (len); - -out: - folio_batch_release(&fbatch); - file_accessed(in); - - return total_spliced ? total_spliced : error; -} - /** * generic_file_splice_read - splice data from file to a pipe * @in: file to splice from @@ -524,13 +394,32 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, struct pipe_inode_info *pipe, size_t len, unsigned int flags) { - if (unlikely(*ppos >= file_inode(in)->i_sb->s_maxbytes)) - return 0; - if (unlikely(!len)) - return 0; + struct iov_iter to; + struct kiocb kiocb; + int ret; + if (in->f_flags & O_DIRECT) return generic_file_direct_splice_read(in, ppos, pipe, len, flags); - return generic_file_buffered_splice_read(in, ppos, pipe, len, flags); + + iov_iter_pipe(&to, ITER_DEST, pipe, len); + init_sync_kiocb(&kiocb, in); + kiocb.ki_pos = *ppos; + ret = call_read_iter(in, &kiocb, &to); + if (ret > 0) { + *ppos = kiocb.ki_pos; + file_accessed(in); + } else if (ret < 0) { + /* free what was emitted */ + pipe_discard_from(pipe, to.start_head); + /* + * callers of ->splice_read() expect -EAGAIN on + * "can't put anything in there", rather than -EFAULT. + */ + if (ret == -EFAULT) + ret = -EAGAIN; + } + + return ret; } EXPORT_SYMBOL(generic_file_splice_read);