istream-mmap.c revision 0dffa25d211be541ee3c953b23566a1a990789df
/* Copyright (c) 2002-2016 Dovecot authors, see the included COPYING file */
#include "lib.h"
#include "ioloop.h"
#include "mmap-util.h"
#include "istream-private.h"
#include <unistd.h>
#include <sys/stat.h>
struct mmap_istream {
struct istream_private istream;
struct timeval fstat_cache_stamp;
void *mmap_base;
off_t mmap_offset;
uoff_t v_size;
bool autoclose_fd:1;
};
static size_t mmap_pagemask = 0;
static void i_stream_mmap_close(struct iostream_private *stream,
bool close_parent ATTR_UNUSED)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
if (mstream->autoclose_fd && mstream->istream.fd != -1) {
if (close(mstream->istream.fd) < 0) {
i_error("mmap_istream.close(%s) failed: %m",
i_stream_get_name(&mstream->istream.istream));
}
}
mstream->istream.fd = -1;
}
static void i_stream_munmap(struct mmap_istream *mstream)
{
struct istream_private *_stream = &mstream->istream;
if (_stream->buffer != NULL) {
if (munmap(mstream->mmap_base, _stream->buffer_size) < 0) {
i_error("mmap_istream.munmap(%s) failed: %m",
i_stream_get_name(&_stream->istream));
}
mstream->mmap_base = NULL;
_stream->buffer = NULL;
_stream->buffer_size = 0;
mstream->mmap_offset = 0;
}
}
static void i_stream_mmap_destroy(struct iostream_private *stream)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
i_stream_munmap(mstream);
}
static size_t mstream_get_mmap_block_size(struct istream_private *stream)
{
return (stream->max_buffer_size + mmap_get_page_size() - 1) & ~
(mmap_get_page_size() - 1);
}
static ssize_t i_stream_mmap_read(struct istream_private *stream)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
size_t aligned_skip;
uoff_t top;
if (stream->pos < stream->buffer_size) {
/* more bytes available without needing to mmap() */
stream->pos = stream->buffer_size;
return stream->pos - stream->skip;
}
if (stream->istream.v_offset >= mstream->v_size) {
stream->istream.eof = TRUE;
return -1;
}
aligned_skip = stream->skip & ~mmap_pagemask;
if (aligned_skip == 0 && mstream->mmap_base != NULL) {
/* didn't skip enough bytes */
return -2;
}
stream->skip -= aligned_skip;
mstream->mmap_offset += aligned_skip;
if (mstream->mmap_base != NULL) {
if (munmap(mstream->mmap_base, stream->buffer_size) < 0) {
i_error("mmap_istream.munmap(%s) failed: %m",
i_stream_get_name(&stream->istream));
}
}
top = mstream->v_size - mstream->mmap_offset;
stream->buffer_size = I_MIN(top, mstream_get_mmap_block_size(stream));
i_assert((uoff_t)mstream->mmap_offset + stream->buffer_size <=
mstream->v_size);
if (stream->buffer_size == 0) {
/* don't bother even trying mmap */
mstream->mmap_base = NULL;
stream->buffer = NULL;
} else {
mstream->mmap_base =
mmap(NULL, stream->buffer_size, PROT_READ, MAP_PRIVATE,
stream->fd, mstream->mmap_offset);
if (mstream->mmap_base == MAP_FAILED) {
i_assert(errno != 0);
stream->istream.stream_errno = errno;
mstream->mmap_base = NULL;
stream->buffer = NULL;
stream->buffer_size = 0;
stream->skip = stream->pos = 0;
io_stream_set_error(&stream->iostream,
"mmap() failed: %m");
i_error("mmap_istream.mmap(%s) failed: %m",
i_stream_get_name(&stream->istream));
return -1;
}
stream->buffer = mstream->mmap_base;
}
if (stream->buffer_size > mmap_get_page_size()) {
if (madvise(mstream->mmap_base, stream->buffer_size,
MADV_SEQUENTIAL) < 0) {
i_error("mmap_istream.madvise(%s): %m",
i_stream_get_name(&stream->istream));
}
}
stream->pos = stream->buffer_size;
i_assert(stream->pos - stream->skip > 0);
return stream->pos - stream->skip;
}
static void i_stream_mmap_seek(struct istream_private *stream, uoff_t v_offset,
bool mark ATTR_UNUSED)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
if (stream->buffer_size != 0 &&
(uoff_t)mstream->mmap_offset <= v_offset &&
(uoff_t)mstream->mmap_offset + stream->buffer_size > v_offset) {
/* already mmaped */
stream->skip = stream->pos = v_offset - mstream->mmap_offset;
} else {
/* force reading next time */
i_stream_munmap(mstream);
stream->skip = stream->pos = v_offset;
}
stream->istream.v_offset = v_offset;
}
static void i_stream_mmap_sync(struct istream_private *stream)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
i_stream_munmap(mstream);
stream->skip = stream->pos = stream->istream.v_offset;
mstream->fstat_cache_stamp.tv_sec = 0;
}
static int fstat_cached(struct mmap_istream *mstream)
{
if (mstream->fstat_cache_stamp.tv_sec == ioloop_timeval.tv_sec &&
mstream->fstat_cache_stamp.tv_usec == ioloop_timeval.tv_usec)
return 0;
if (fstat(mstream->istream.fd, &mstream->istream.statbuf) < 0) {
i_error("mmap_istream.fstat(%s) failed: %m",
i_stream_get_name(&mstream->istream.istream));
return -1;
}
mstream->fstat_cache_stamp = ioloop_timeval;
return 0;
}
static int
i_stream_mmap_stat(struct istream_private *stream, bool exact ATTR_UNUSED)
{
struct mmap_istream *mstream = (struct mmap_istream *) stream;
return fstat_cached(mstream);
}
struct istream *i_stream_create_mmap(int fd, size_t block_size,
uoff_t start_offset, uoff_t v_size,
bool autoclose_fd)
{
struct mmap_istream *mstream;
struct istream *istream;
struct stat st;
if (mmap_pagemask == 0)
mmap_pagemask = mmap_get_page_size()-1;
if (v_size == 0) {
if (fstat(fd, &st) < 0)
i_error("i_stream_create_mmap(): fstat() failed: %m");
else {
v_size = st.st_size;
if (start_offset > v_size)
start_offset = v_size;
v_size -= start_offset;
}
}
mstream = i_new(struct mmap_istream, 1);
mstream->autoclose_fd = autoclose_fd;
mstream->v_size = v_size;
mstream->istream.iostream.close = i_stream_mmap_close;
mstream->istream.iostream.destroy = i_stream_mmap_destroy;
mstream->istream.max_buffer_size = block_size;
mstream->istream.read = i_stream_mmap_read;
mstream->istream.seek = i_stream_mmap_seek;
mstream->istream.sync = i_stream_mmap_sync;
mstream->istream.stat = i_stream_mmap_stat;
mstream->istream.istream.readable_fd = TRUE;
mstream->istream.start_offset = start_offset;
istream = i_stream_create(&mstream->istream, NULL, fd);
istream->mmaped = TRUE;
istream->blocking = TRUE;
istream->seekable = TRUE;
return istream;
}