diff for duplicates of <20150327093046.53c2769a.akpm@linux-foundation.org> diff --git a/a/1.txt b/N1/1.txt index f6320be..7f6c200 100644 --- a/a/1.txt +++ b/N1/1.txt @@ -35,7 +35,7 @@ On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@pu > ret < size_wanted means only part of the file > is in cache. ->From my reading of the code, pread2() will return -EAGAIN only when it +From my reading of the code, pread2() will return -EAGAIN only when it copied zero bytes to userspace. ie, the very first page wasn't in cache. If pread2() does copy some data to userspace then it will return the amount of data copied. This is traditional read() diff --git a/a/content_digest b/N1/content_digest index fbe2aaa..f5b5754 100644 --- a/a/content_digest +++ b/N1/content_digest @@ -63,7 +63,7 @@ "> ret < size_wanted means only part of the file\n" "> is in cache.\n" "\n" - ">From my reading of the code, pread2() will return -EAGAIN only when it\n" + "From my reading of the code, pread2() will return -EAGAIN only when it\n" "copied zero bytes to userspace. ie, the very first page wasn't in\n" "cache. If pread2() does copy some data to userspace then it will\n" "return the amount of data copied. This is traditional read()\n" @@ -101,4 +101,4 @@ "EWOULDBLOCK? They have the same numerical value, but EWOULDBLOCK is a\n" "better name - EAGAIN says \"run it again\", but that won't work." -04ba29791b937ab3e500f2a923aaf350a53a7adf6f28324f794981c448a6a54c +5c09367918f4fae1a7536dfc98f5a5a580745eccf533faa857e326bdb8e1c287
diff --git a/a/1.txt b/N2/1.txt index f6320be..6da43c6 100644 --- a/a/1.txt +++ b/N2/1.txt @@ -1,7 +1,7 @@ -On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote: +On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra@samba.org> wrote: > On Fri, Mar 27, 2015 at 02:01:59AM -0700, Andrew Morton wrote: -> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote: +> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch@infradead.org> wrote: > > > > > On Fri, Mar 27, 2015 at 01:35:16AM -0700, Andrew Morton wrote: > > > > fincore() doesn't have to be ugly. Please address the design issues I @@ -34,41 +34,3 @@ On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@pu > The thing I want to avoid is the case where > ret < size_wanted means only part of the file > is in cache. - ->From my reading of the code, pread2() will return -EAGAIN only when it -copied zero bytes to userspace. ie, the very first page wasn't in -cache. If pread2() does copy some data to userspace then it will -return the amount of data copied. This is traditional read() -behaviour. - -Maybe there's some other code somewhere in the patch which converts -that short read into -EAGAIN, dunno - the changelogs don't appear to -mention it and the manpage update is ambiguous about this. - -But from an interface perspective the behaviour you're asking for is -insane, frankly - if the kernel copied out 8k of data then pread2() -should return 8k. Otherwise there's no way for userspace to know that -the 8k copy actually happened and we have just wasted a great pile of -CPU doing a pointless memcpy. - -I expect that this situation (first part in cache, latter part not in -cache) is rare - for reasonably small requests the common cases will be -"all cached" and "nothing cached". So perhaps the best approach here -is for samba to add special handling for the short read, to work out -the reason for its occurrence. - -Alternatively we could add another flag to pread2() to select this -"throw away my data and return -EAGAIN" behaviour. Presumably -implemented with an i_size check, but it's gonna be racy. - - - -I take it from your comments that nobody has actually wired up pread2() -into samba yet? That's a bit disturbing, because if we later want to -go and change something like this short-read behaviour, we're screwed - -it's a non back-compat userspace-visible change. - - -And a note on cosmetics: why are we using EAGAIN here rather than -EWOULDBLOCK? They have the same numerical value, but EWOULDBLOCK is a -better name - EAGAIN says "run it again", but that won't work. diff --git a/a/content_digest b/N2/content_digest index fbe2aaa..d7cd129 100644 --- a/a/content_digest +++ b/N2/content_digest @@ -5,31 +5,31 @@ "ref\020150327084833.GA7689@infradead.org\0" "ref\020150327020159.eadd0ce1.akpm@linux-foundation.org\0" "ref\020150327155854.GA5548@samba2\0" - "From\0Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>\0" + "From\0Andrew Morton <akpm@linux-foundation.org>\0" "Subject\0Re: [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only)\0" "Date\0Fri, 27 Mar 2015 09:30:46 -0700\0" - "To\0Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>\0" - "Cc\0Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>" - Milosz Tanski <milosz-B5zB6C1i6pkAvxtiuMwx3w@public.gmane.org> - linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - linux-aio-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org - Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org> - Volker Lendecke <Volker.Lendecke-3ekOc4rQMZmzQB+pC5nmwQ@public.gmane.org> - Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> - Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> - Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org> - Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org> - linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> - linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - " Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>\0" + "To\0Jeremy Allison <jra@samba.org>\0" + "Cc\0Christoph Hellwig <hch@infradead.org>" + Milosz Tanski <milosz@adfin.com> + linux-kernel@vger.kernel.org + linux-fsdevel@vger.kernel.org + linux-aio@kvack.org + Mel Gorman <mgorman@suse.de> + Volker Lendecke <Volker.Lendecke@sernet.de> + Tejun Heo <tj@kernel.org> + Jeff Moyer <jmoyer@redhat.com> + Theodore Ts'o <tytso@mit.edu> + Al Viro <viro@zeniv.linux.org.uk> + linux-api@vger.kernel.org + Michael Kerrisk <mtk.manpages@gmail.com> + linux-arch@vger.kernel.org + " Dave Chinner <david@fromorbit.com>\0" "\00:1\0" "b\0" - "On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote:\n" + "On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra@samba.org> wrote:\n" "\n" "> On Fri, Mar 27, 2015 at 02:01:59AM -0700, Andrew Morton wrote:\n" - "> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote:\n" + "> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch@infradead.org> wrote:\n" "> > \n" "> > > On Fri, Mar 27, 2015 at 01:35:16AM -0700, Andrew Morton wrote:\n" "> > > > fincore() doesn't have to be ugly. Please address the design issues I\n" @@ -61,44 +61,6 @@ "> \n" "> The thing I want to avoid is the case where\n" "> ret < size_wanted means only part of the file\n" - "> is in cache.\n" - "\n" - ">From my reading of the code, pread2() will return -EAGAIN only when it\n" - "copied zero bytes to userspace. ie, the very first page wasn't in\n" - "cache. If pread2() does copy some data to userspace then it will\n" - "return the amount of data copied. This is traditional read()\n" - "behaviour.\n" - "\n" - "Maybe there's some other code somewhere in the patch which converts\n" - "that short read into -EAGAIN, dunno - the changelogs don't appear to\n" - "mention it and the manpage update is ambiguous about this.\n" - "\n" - "But from an interface perspective the behaviour you're asking for is\n" - "insane, frankly - if the kernel copied out 8k of data then pread2()\n" - "should return 8k. Otherwise there's no way for userspace to know that\n" - "the 8k copy actually happened and we have just wasted a great pile of\n" - "CPU doing a pointless memcpy.\n" - "\n" - "I expect that this situation (first part in cache, latter part not in\n" - "cache) is rare - for reasonably small requests the common cases will be\n" - "\"all cached\" and \"nothing cached\". So perhaps the best approach here\n" - "is for samba to add special handling for the short read, to work out\n" - "the reason for its occurrence.\n" - "\n" - "Alternatively we could add another flag to pread2() to select this\n" - "\"throw away my data and return -EAGAIN\" behaviour. Presumably\n" - "implemented with an i_size check, but it's gonna be racy.\n" - "\n" - "\n" - "\n" - "I take it from your comments that nobody has actually wired up pread2()\n" - "into samba yet? That's a bit disturbing, because if we later want to\n" - "go and change something like this short-read behaviour, we're screwed -\n" - "it's a non back-compat userspace-visible change.\n" - "\n" - "\n" - "And a note on cosmetics: why are we using EAGAIN here rather than\n" - "EWOULDBLOCK? They have the same numerical value, but EWOULDBLOCK is a\n" - "better name - EAGAIN says \"run it again\", but that won't work." + > is in cache. -04ba29791b937ab3e500f2a923aaf350a53a7adf6f28324f794981c448a6a54c +c042126978e9e254a7741222e660904ca0bfa9ab521b70f1c4f0f88f7eaa102d
diff --git a/a/1.txt b/N3/1.txt index f6320be..55a322d 100644 --- a/a/1.txt +++ b/N3/1.txt @@ -1,7 +1,7 @@ -On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote: +On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra@samba.org> wrote: > On Fri, Mar 27, 2015 at 02:01:59AM -0700, Andrew Morton wrote: -> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote: +> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch@infradead.org> wrote: > > > > > On Fri, Mar 27, 2015 at 01:35:16AM -0700, Andrew Morton wrote: > > > > fincore() doesn't have to be ugly. Please address the design issues I diff --git a/a/content_digest b/N3/content_digest index fbe2aaa..9c2bd0d 100644 --- a/a/content_digest +++ b/N3/content_digest @@ -5,31 +5,31 @@ "ref\020150327084833.GA7689@infradead.org\0" "ref\020150327020159.eadd0ce1.akpm@linux-foundation.org\0" "ref\020150327155854.GA5548@samba2\0" - "From\0Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>\0" + "From\0Andrew Morton <akpm@linux-foundation.org>\0" "Subject\0Re: [PATCH v7 0/5] vfs: Non-blockling buffered fs read (page cache only)\0" "Date\0Fri, 27 Mar 2015 09:30:46 -0700\0" - "To\0Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>\0" - "Cc\0Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>" - Milosz Tanski <milosz-B5zB6C1i6pkAvxtiuMwx3w@public.gmane.org> - linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - linux-aio-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org - Mel Gorman <mgorman-l3A5Bk7waGM@public.gmane.org> - Volker Lendecke <Volker.Lendecke-3ekOc4rQMZmzQB+pC5nmwQ@public.gmane.org> - Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> - Jeff Moyer <jmoyer-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org> - Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org> - Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org> - linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> - linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org - " Dave Chinner <david-FqsqvQoI3Ljby3iVrkZq2A@public.gmane.org>\0" + "To\0Jeremy Allison <jra@samba.org>\0" + "Cc\0Christoph Hellwig <hch@infradead.org>" + Milosz Tanski <milosz@adfin.com> + linux-kernel@vger.kernel.org + linux-fsdevel@vger.kernel.org + linux-aio@kvack.org + Mel Gorman <mgorman@suse.de> + Volker Lendecke <Volker.Lendecke@sernet.de> + Tejun Heo <tj@kernel.org> + Jeff Moyer <jmoyer@redhat.com> + Theodore Ts'o <tytso@mit.edu> + Al Viro <viro@zeniv.linux.org.uk> + linux-api@vger.kernel.org + Michael Kerrisk <mtk.manpages@gmail.com> + linux-arch@vger.kernel.org + " Dave Chinner <david@fromorbit.com>\0" "\00:1\0" "b\0" - "On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org> wrote:\n" + "On Fri, 27 Mar 2015 08:58:54 -0700 Jeremy Allison <jra@samba.org> wrote:\n" "\n" "> On Fri, Mar 27, 2015 at 02:01:59AM -0700, Andrew Morton wrote:\n" - "> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org> wrote:\n" + "> > On Fri, 27 Mar 2015 01:48:33 -0700 Christoph Hellwig <hch@infradead.org> wrote:\n" "> > \n" "> > > On Fri, Mar 27, 2015 at 01:35:16AM -0700, Andrew Morton wrote:\n" "> > > > fincore() doesn't have to be ugly. Please address the design issues I\n" @@ -101,4 +101,4 @@ "EWOULDBLOCK? They have the same numerical value, but EWOULDBLOCK is a\n" "better name - EAGAIN says \"run it again\", but that won't work." -04ba29791b937ab3e500f2a923aaf350a53a7adf6f28324f794981c448a6a54c +7d2cdbe69cd87e744b10f48255813cf8451822b37ee3e5a78961f53aa6db2a93
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