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indexer: Avoid one `mmap(2)`/`munmap(2)` pair per `git_indexer_append` call by lhchavez · Pull Request #6039 · libgit2/libgit2 · GitHub

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indexer: Avoid one mmap(2)/munmap(2) pair per git_indexer_append call #6039

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Merged
ethomson merged 4 commits into from
Sep 14, 2021
Conversation 7 Commits 4 Checks 0 Files changed
Merged

indexer: Avoid one mmap(2)/munmap(2) pair per git_indexer_append call #6039

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66a75fd
indexer: Avoid one `mmap(2)`/`munmap(2)` pair per `git_indexer_append…
lhchavez Sep 7, 2021
eeceaac
Also remove a `ftruncate(2)` call in `git_indexer_commit`
lhchavez Sep 7, 2021
6571ba7
Only avoid `mmap(2)`/`ftruncate(2)` when in non-Windows
lhchavez Sep 8, 2021
c65eb24
Avoid double negatives in the justification for truncation
lhchavez Sep 8, 2021
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40 changes: 37 additions & 3 deletions src/indexer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -601,9 +601,10 @@ static void hash_partially(git_indexer *idx, const uint8_t *data, size_t size)
idx->inbuf_len += size - to_expell;
}

#if defined(NO_MMAP) || !defined(GIT_WIN32)

static int write_at(git_indexer *idx, const void *data, off64_t offset, size_t size)
{
#ifdef NO_MMAP
size_t remaining_size = size;
const char *ptr = (const char *)data;

Expand All @@ -619,7 +620,31 @@ static int write_at(git_indexer *idx, const void *data, off64_t offset, size_t s
offset += nb;
remaining_size -= nb;
}

return 0;
}

static int append_to_pack(git_indexer *idx, const void *data, size_t size)
{
if (write_at(idx, data, idx->pack->mwf.size, size) < 0) {
git_error_set(GIT_ERROR_OS, "cannot extend packfile '%s'", idx->pack->pack_name);
return -1;
}

return 0;
}

#else

/*
* Windows may keep different views to a networked file for the mmap- and
* open-accessed versions of a file, so any writes done through
* `write(2)`/`pwrite(2)` may not be reflected on the data that `mmap(2)` is
* able to read.
*/

static int write_at(git_indexer *idx, const void *data, off64_t offset, size_t size)
{
git_file fd = idx->pack->mwf.fd;
size_t mmap_alignment;
size_t page_offset;
Expand All @@ -644,7 +669,6 @@ static int write_at(git_indexer *idx, const void *data, off64_t offset, size_t s
map_data = (unsigned char *)map.data;
memcpy(map_data + page_offset, data, size);
p_munmap(&map);
#endif

return 0;
}
Expand Down Expand Up @@ -680,6 +704,8 @@ static int append_to_pack(git_indexer *idx, const void *data, size_t size)
return write_at(idx, data, idx->pack->mwf.size, size);
}

#endif

static int read_stream_object(git_indexer *idx, git_indexer_progress *stats)
{
git_packfile_stream *stream = &idx->stream;
Expand Down Expand Up @@ -1279,11 +1305,19 @@ int git_indexer_commit(git_indexer *idx, git_indexer_progress *stats)
if (git_mwindow_free_all(&idx->pack->mwf) < 0)
goto on_error;

/* Truncate file to undo rounding up to next page_size in append_to_pack */
#if !defined(NO_MMAP) && defined(GIT_WIN32)
/*
* Some non-Windows remote filesystems fail when truncating files if the
* file permissions change after opening the file (done by p_mkstemp).
*
* Truncation is only needed when mmap is used to undo rounding up to next
* page_size in append_to_pack.
*/
if (p_ftruncate(idx->pack->mwf.fd, idx->pack->mwf.size) < 0) {
git_error_set(GIT_ERROR_OS, "failed to truncate pack file '%s'", idx->pack->pack_name);
return -1;
}
#endif

if (idx->do_fsync && p_fsync(idx->pack->mwf.fd) < 0) {
git_error_set(GIT_ERROR_OS, "failed to fsync packfile");
Expand Down
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