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Tue, 21 Mar 2023 21:15:53 -0400 X-MC-Unique: M3QeEbI_OTOy-_W1UUrLAw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 14D2D3806106; Wed, 22 Mar 2023 01:15:53 +0000 (UTC) Received: from localhost (ovpn-13-195.pek2.redhat.com [10.72.13.195]) by smtp.corp.redhat.com (Postfix) with ESMTPS id E41496B590; Wed, 22 Mar 2023 01:15:51 +0000 (UTC) Date: Wed, 22 Mar 2023 09:15:48 +0800 From: Baoquan He To: Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro Subject: Re: [PATCH v4 2/4] fs/proc/kcore: convert read_kcore() to read_kcore_iter() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 9E1B2140015 X-Stat-Signature: rxuezhhi9tyo5cy4hp9r3tr6eusor6ui X-HE-Tag: 1679447758-661413 X-HE-Meta: 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 sef/Km6C U/eWSArm08bMYF0qEfNaVWmtPQKhmEaoDbIFlOP8aviMxmEo/Tu4XdrugIoths8qpTEMujtcEKIKzbUvIfGBwSZDOzj7J7K2gsKfm7V9jxDqHnjbfsZxkZeGJSY7dw85y8xtw3/XI/Y+/rH1uo/agVr0VrxsODeydWVL+5/etv/nTYscTe1cNflz57A6bW0UrhKB6Oh2wIFPwD3gXi73seN2OUElhsrk43X4v9tMmYuYAfwUaW2L0/DMd2eAUTmc0y7Vm5vnw3wZfqWULruYLHF0qAW/mCUBV3xGa 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: Hi Lorenzo, On 03/21/23 at 08:54pm, Lorenzo Stoakes wrote: > Now we have eliminated spinlocks from the vread() case, convert > read_kcore() to read_kcore_iter(). Sorry for late comment. Here I could miss something important, I don't get where we have eliminated spinlocks from the vread() case. Do I misunderstand this sentence? > > For the time being we still use a bounce buffer for vread(), however in the > next patch we will convert this to interact directly with the iterator and > eliminate the bounce buffer altogether. > > Signed-off-by: Lorenzo Stoakes > --- > fs/proc/kcore.c | 58 ++++++++++++++++++++++++------------------------- > 1 file changed, 29 insertions(+), 29 deletions(-) > > diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c > index 556f310d6aa4..25e0eeb8d498 100644 > --- a/fs/proc/kcore.c > +++ b/fs/proc/kcore.c > @@ -24,7 +24,7 @@ > #include > #include > #include > -#include > +#include > #include > #include > #include > @@ -308,9 +308,12 @@ static void append_kcore_note(char *notes, size_t *i, const char *name, > } > > static ssize_t > -read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > +read_kcore_iter(struct kiocb *iocb, struct iov_iter *iter) > { > + struct file *file = iocb->ki_filp; > char *buf = file->private_data; > + loff_t *ppos = &iocb->ki_pos; > + > size_t phdrs_offset, notes_offset, data_offset; > size_t page_offline_frozen = 1; > size_t phdrs_len, notes_len; > @@ -318,6 +321,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > size_t tsz; > int nphdr; > unsigned long start; > + size_t buflen = iov_iter_count(iter); > size_t orig_buflen = buflen; > int ret = 0; > > @@ -333,7 +337,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > notes_offset = phdrs_offset + phdrs_len; > > /* ELF file header. */ > - if (buflen && *fpos < sizeof(struct elfhdr)) { > + if (buflen && *ppos < sizeof(struct elfhdr)) { > struct elfhdr ehdr = { > .e_ident = { > [EI_MAG0] = ELFMAG0, > @@ -355,19 +359,18 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > .e_phnum = nphdr, > }; > > - tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *fpos); > - if (copy_to_user(buffer, (char *)&ehdr + *fpos, tsz)) { > + tsz = min_t(size_t, buflen, sizeof(struct elfhdr) - *ppos); > + if (copy_to_iter((char *)&ehdr + *ppos, tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > > - buffer += tsz; > buflen -= tsz; > - *fpos += tsz; > + *ppos += tsz; > } > > /* ELF program headers. */ > - if (buflen && *fpos < phdrs_offset + phdrs_len) { > + if (buflen && *ppos < phdrs_offset + phdrs_len) { > struct elf_phdr *phdrs, *phdr; > > phdrs = kzalloc(phdrs_len, GFP_KERNEL); > @@ -397,22 +400,21 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > phdr++; > } > > - tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *fpos); > - if (copy_to_user(buffer, (char *)phdrs + *fpos - phdrs_offset, > - tsz)) { > + tsz = min_t(size_t, buflen, phdrs_offset + phdrs_len - *ppos); > + if (copy_to_iter((char *)phdrs + *ppos - phdrs_offset, tsz, > + iter) != tsz) { > kfree(phdrs); > ret = -EFAULT; > goto out; > } > kfree(phdrs); > > - buffer += tsz; > buflen -= tsz; > - *fpos += tsz; > + *ppos += tsz; > } > > /* ELF note segment. */ > - if (buflen && *fpos < notes_offset + notes_len) { > + if (buflen && *ppos < notes_offset + notes_len) { > struct elf_prstatus prstatus = {}; > struct elf_prpsinfo prpsinfo = { > .pr_sname = 'R', > @@ -447,24 +449,23 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > vmcoreinfo_data, > min(vmcoreinfo_size, notes_len - i)); > > - tsz = min_t(size_t, buflen, notes_offset + notes_len - *fpos); > - if (copy_to_user(buffer, notes + *fpos - notes_offset, tsz)) { > + tsz = min_t(size_t, buflen, notes_offset + notes_len - *ppos); > + if (copy_to_iter(notes + *ppos - notes_offset, tsz, iter) != tsz) { > kfree(notes); > ret = -EFAULT; > goto out; > } > kfree(notes); > > - buffer += tsz; > buflen -= tsz; > - *fpos += tsz; > + *ppos += tsz; > } > > /* > * Check to see if our file offset matches with any of > * the addresses in the elf_phdr on our list. > */ > - start = kc_offset_to_vaddr(*fpos - data_offset); > + start = kc_offset_to_vaddr(*ppos - data_offset); > if ((tsz = (PAGE_SIZE - (start & ~PAGE_MASK))) > buflen) > tsz = buflen; > > @@ -497,7 +498,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > } > > if (!m) { > - if (clear_user(buffer, tsz)) { > + if (iov_iter_zero(tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > @@ -508,14 +509,14 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > case KCORE_VMALLOC: > vread(buf, (char *)start, tsz); > /* we have to zero-fill user buffer even if no read */ > - if (copy_to_user(buffer, buf, tsz)) { > + if (copy_to_iter(buf, tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > break; > case KCORE_USER: > /* User page is handled prior to normal kernel page: */ > - if (copy_to_user(buffer, (char *)start, tsz)) { > + if (copy_to_iter((char *)start, tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > @@ -531,7 +532,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > */ > if (!page || PageOffline(page) || > is_page_hwpoison(page) || !pfn_is_ram(pfn)) { > - if (clear_user(buffer, tsz)) { > + if (iov_iter_zero(tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > @@ -541,25 +542,24 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos) > case KCORE_VMEMMAP: > case KCORE_TEXT: > /* > - * We use _copy_to_user() to bypass usermode hardening > + * We use _copy_to_iter() to bypass usermode hardening > * which would otherwise prevent this operation. > */ > - if (_copy_to_user(buffer, (char *)start, tsz)) { > + if (_copy_to_iter((char *)start, tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > break; > default: > pr_warn_once("Unhandled KCORE type: %d\n", m->type); > - if (clear_user(buffer, tsz)) { > + if (iov_iter_zero(tsz, iter) != tsz) { > ret = -EFAULT; > goto out; > } > } > skip: > buflen -= tsz; > - *fpos += tsz; > - buffer += tsz; > + *ppos += tsz; > start += tsz; > tsz = (buflen > PAGE_SIZE ? PAGE_SIZE : buflen); > } > @@ -603,7 +603,7 @@ static int release_kcore(struct inode *inode, struct file *file) > } > > static const struct proc_ops kcore_proc_ops = { > - .proc_read = read_kcore, > + .proc_read_iter = read_kcore_iter, > .proc_open = open_kcore, > .proc_release = release_kcore, > .proc_lseek = default_llseek, > -- > 2.39.2 >