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ircd::fs: Abstract the posix_fadvise wrapping.

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This commit is contained in:
Jason Volk 2019-05-03 03:33:45 -07:00
parent 9cca4c6a5d
commit d544c37d3d
2 changed files with 16 additions and 2 deletions
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2
include/ircd/fs/read.h
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@ -30,7 +30,7 @@ namespace ircd::fs
// Test whether bytes in the specified range are cached and should not block
bool fincore(const fd &, const size_t &, const read_opts & = read_opts_default);
// Prefetch bytes for subsequent read(); offset is given in opts.
// Prefetch data for subsequent read(); offset given in opts (WILLNEED).
size_t prefetch(const fd &, const size_t &, const read_opts & = read_opts_default);
}

16
ircd/fs.cc
View file

@ -476,6 +476,11 @@ ircd::fs::flush(const fd &fd,
// fs/read.h
//
namespace ircd::fs
{
static size_t advise(const fd &, const size_t &, const read_opts &, const int &advice);
}
ircd::fs::read_opts
const ircd::fs::read_opts_default
{};
@ -484,6 +489,15 @@ size_t
ircd::fs::prefetch(const fd &fd,
const size_t &count,
const read_opts &opts)
{
return advise(fd, count, opts, POSIX_FADV_WILLNEED);
}
size_t
ircd::fs::advise(const fd &fd,
const size_t &count,
const read_opts &opts,
const int &advice)
{
static const size_t max_count
{
@ -494,7 +508,7 @@ ircd::fs::prefetch(const fd &fd,
{
off = opts.offset + max_count * i++;
cnt = std::min(opts.offset + count - off, max_count);
switch(const auto r(::posix_fadvise(fd, off, cnt, POSIX_FADV_WILLNEED)); r)
switch(const auto r(::posix_fadvise(fd, off, cnt, advice)); r)
{
case 0: break;
default: throw_system_error(r);