Date: Fri, 20 Aug 2021 23:33:24 +0800 From: Ka Ho Ng <khng@FreeBSD.org> To: freebsd-fs@FreeBSD.org Subject: Re: fspacectl(2): result of rmsr.r_offset for a success and non-partial operation Message-ID: <29087ddc-9b46-15fa-4041-c3a50dcf99db@FreeBSD.org> In-Reply-To: <87d4a87d-2ee3-74dd-3689-94dc0daf3983@FreeBSD.org> References: <87d4a87d-2ee3-74dd-3689-94dc0daf3983@FreeBSD.org>
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On 2021/8/20 11:23 PM, Ka Ho Ng wrote: > There were some recent discussion in https://reviews.freebsd.org/D31604 > around the returned value of rmsr.r_offset. For a complete and > successful operation, rmsr.r_len is set to 0. Regarding rmsr.r_offset, > the bottom line is to have rmsr.r_offset being no greater than current > file size in case rmsr.r_offset is greater than file size, while leaving > rmsr.r_offset to be within EOF in case rqsr.r_offset is not beyond EOF. > > With the current approach, rmsr.r_offset is loosely defined as file > system is free to set it to some value as long as it is neither smaller > than rqsr.r_offset (in case rqsr.r_offset is within EOF), or beyond EOF > (in case rqsr.r_offset is beyond EOF). Do you think it is a good idea to > make it stricter in case the call succeeds and rmsr.r_len == 0 (i.e. a > complete operation)? If that is the case, what if we set rmsr.r_offset > to be rqsr.r_offset + rqsr.r_len? > > Ka Ho > My another approach is to explicitly document that for a complete and successful operation (i.e. rmsr.r_len == 0) callers need not to consider the exact value of rmsr.r_offset, except if the operation range is not complete outside of EOF, rmsr.r_offset is not going to be outside of EOF either. Ka Ho
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