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[70.29.85.38]) by smtp.gmail.com with ESMTPSA id z26sm9830251ioi.85.2019.07.05.07.38.49 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 05 Jul 2019 07:38:50 -0700 (PDT) Sender: Mark Johnston Date: Fri, 5 Jul 2019 10:38:45 -0400 From: Mark Johnston To: Rick Macklem Cc: "freebsd-current@FreeBSD.org" , "kib@freebsd.org" , Alan Somers Subject: Re: should a copy_file_range(2) syscall be interrupted via a signal Message-ID: <20190705143845.GA50901@raichu> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.0 (2019-05-25) X-Rspamd-Queue-Id: AA2A971F97 X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=Spqx/A+G; spf=pass (mx1.freebsd.org: domain of markjdb@gmail.com designates 2607:f8b0:4864:20::d43 as permitted sender) smtp.mailfrom=markjdb@gmail.com X-Spamd-Result: default: False [-3.06 / 15.00]; TO_DN_EQ_ADDR_SOME(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; TO_DN_SOME(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36]; RCVD_COUNT_THREE(0.00)[3]; DKIM_TRACE(0.00)[gmail.com:+]; MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com]; NEURAL_HAM_SHORT(-0.54)[-0.542,0]; FORGED_SENDER(0.30)[markj@freebsd.org,markjdb@gmail.com]; MIME_TRACE(0.00)[0:+]; RCVD_TLS_LAST(0.00)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; FROM_NEQ_ENVFROM(0.00)[markj@freebsd.org,markjdb@gmail.com]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-0.999,0]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; MIME_GOOD(-0.10)[text/plain]; DMARC_NA(0.00)[freebsd.org]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RCVD_IN_DNSWL_NONE(0.00)[3.4.d.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.4.6.8.4.0.b.8.f.7.0.6.2.list.dnswl.org : 127.0.5.0]; IP_SCORE(-0.81)[ip: (1.57), ipnet: 2607:f8b0::/32(-3.16), asn: 15169(-2.40), country: US(-0.06)]; MID_RHS_NOT_FQDN(0.50)[] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 05 Jul 2019 14:38:52 -0000 On Fri, Jul 05, 2019 at 12:28:51AM +0000, Rick Macklem wrote: > Hi, > > I have been working on a Linux compatible copy_file_range(2) syscall > (the current code can be found at https://reviews.freebsd.org/D20584). > > One outstanding issue is how it should deal with signals. > Right now, I have vn_start_write() without PCATCH, so that it won't be > interrupted by a signal, but I notice that vn_write() {ie. write syscall } does > have PCATCH on vn_start_write() and so does vn_rdwr() when it is called > without IO_NODELOCKED. > > I am thinking that copy_file_range(2) should do this also. > However, if it returns an error, it is impossible for the caller to know how much > of the data range got copied. Couldn't copy_file_range() return the number of bytes copied in this case? (The Linux man page notes that short writes are possible.) I would expect to see the same error handling that we have in dofilewrite(), where certain errnos are squashed. > What do you think the copy_file_range(2) code should do? I'd find it surprising if copy_file_range() isn't interruptible.