Date: Mon, 4 May 2015 12:11:37 +0300 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: alc@FreeBSD.org, arch@FreeBSD.org Subject: Re: more strict KPI for vm_pager_get_pages() Message-ID: <20150504091137.GH34544@glebius.int.ru> In-Reply-To: <20150504082426.GC2390@kib.kiev.ua> References: <20150430142408.GS546@nginx.com> <20150504082426.GC2390@kib.kiev.ua>
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On Mon, May 04, 2015 at 11:24:26AM +0300, Konstantin Belousov wrote: K> Below is the summary of my part of the internal discussion about the changes. Quite short. Is it truncated? K> Traditionally, Unix allows the filesystems to perform the short reads. K> Most fundamental change in the patch removes this freedom from the K> filesystem implementation, and I think that only local filesystems could K> be compliant with the proposed strictness. K> K> IMO, the response from vm_pager_haspages() is only advisory, since K> filesystem might not control the external entities which are the source K> of the required data. That's why remote filesystems use vop_stdbmap() (or similar), which always return zeroes for "after" and "before" hints. -- Totus tuus, Glebius.
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