git/csum-file.c
Neeraj Singh 020406eaa5 core.fsync: introduce granular fsync control infrastructure
This commit introduces the infrastructure for the core.fsync
configuration knob. The repository components we want to sync
are identified by flags so that we can turn on or off syncing
for specific components.

If core.fsyncObjectFiles is set and the core.fsync configuration
also includes FSYNC_COMPONENT_LOOSE_OBJECT, we will fsync any
loose objects. This picks the strictest data integrity behavior
if core.fsync and core.fsyncObjectFiles are set to conflicting values.

This change introduces the currently unused fsync_component
helper, which will be used by a later patch that adds fsyncing to
the refs backend.

Actual configuration and documentation of the fsync components
list are in other patches in the series to separate review of
the underlying mechanism from the policy of how it's configured.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2022-03-10 15:10:22 -08:00

232 lines
5.3 KiB
C

/*
* csum-file.c
*
* Copyright (C) 2005 Linus Torvalds
*
* Simple file write infrastructure for writing SHA1-summed
* files. Useful when you write a file that you want to be
* able to verify hasn't been messed with afterwards.
*/
#include "cache.h"
#include "progress.h"
#include "csum-file.h"
static void verify_buffer_or_die(struct hashfile *f,
const void *buf,
unsigned int count)
{
ssize_t ret = read_in_full(f->check_fd, f->check_buffer, count);
if (ret < 0)
die_errno("%s: sha1 file read error", f->name);
if (ret != count)
die("%s: sha1 file truncated", f->name);
if (memcmp(buf, f->check_buffer, count))
die("sha1 file '%s' validation error", f->name);
}
static void flush(struct hashfile *f, const void *buf, unsigned int count)
{
if (0 <= f->check_fd && count)
verify_buffer_or_die(f, buf, count);
if (write_in_full(f->fd, buf, count) < 0) {
if (errno == ENOSPC)
die("sha1 file '%s' write error. Out of diskspace", f->name);
die_errno("sha1 file '%s' write error", f->name);
}
f->total += count;
display_throughput(f->tp, f->total);
}
void hashflush(struct hashfile *f)
{
unsigned offset = f->offset;
if (offset) {
the_hash_algo->update_fn(&f->ctx, f->buffer, offset);
flush(f, f->buffer, offset);
f->offset = 0;
}
}
static void free_hashfile(struct hashfile *f)
{
free(f->buffer);
free(f->check_buffer);
free(f);
}
int finalize_hashfile(struct hashfile *f, unsigned char *result,
enum fsync_component component, unsigned int flags)
{
int fd;
hashflush(f);
the_hash_algo->final_fn(f->buffer, &f->ctx);
if (result)
hashcpy(result, f->buffer);
if (flags & CSUM_HASH_IN_STREAM)
flush(f, f->buffer, the_hash_algo->rawsz);
if (flags & CSUM_FSYNC)
fsync_component_or_die(component, f->fd, f->name);
if (flags & CSUM_CLOSE) {
if (close(f->fd))
die_errno("%s: sha1 file error on close", f->name);
fd = 0;
} else
fd = f->fd;
if (0 <= f->check_fd) {
char discard;
int cnt = read_in_full(f->check_fd, &discard, 1);
if (cnt < 0)
die_errno("%s: error when reading the tail of sha1 file",
f->name);
if (cnt)
die("%s: sha1 file has trailing garbage", f->name);
if (close(f->check_fd))
die_errno("%s: sha1 file error on close", f->name);
}
free_hashfile(f);
return fd;
}
void hashwrite(struct hashfile *f, const void *buf, unsigned int count)
{
while (count) {
unsigned left = f->buffer_len - f->offset;
unsigned nr = count > left ? left : count;
if (f->do_crc)
f->crc32 = crc32(f->crc32, buf, nr);
if (nr == f->buffer_len) {
/*
* Flush a full batch worth of data directly
* from the input, skipping the memcpy() to
* the hashfile's buffer. In this block,
* f->offset is necessarily zero.
*/
the_hash_algo->update_fn(&f->ctx, buf, nr);
flush(f, buf, nr);
} else {
/*
* Copy to the hashfile's buffer, flushing only
* if it became full.
*/
memcpy(f->buffer + f->offset, buf, nr);
f->offset += nr;
left -= nr;
if (!left)
hashflush(f);
}
count -= nr;
buf = (char *) buf + nr;
}
}
struct hashfile *hashfd_check(const char *name)
{
int sink, check;
struct hashfile *f;
sink = xopen("/dev/null", O_WRONLY);
check = xopen(name, O_RDONLY);
f = hashfd(sink, name);
f->check_fd = check;
f->check_buffer = xmalloc(f->buffer_len);
return f;
}
static struct hashfile *hashfd_internal(int fd, const char *name,
struct progress *tp,
size_t buffer_len)
{
struct hashfile *f = xmalloc(sizeof(*f));
f->fd = fd;
f->check_fd = -1;
f->offset = 0;
f->total = 0;
f->tp = tp;
f->name = name;
f->do_crc = 0;
the_hash_algo->init_fn(&f->ctx);
f->buffer_len = buffer_len;
f->buffer = xmalloc(buffer_len);
f->check_buffer = NULL;
return f;
}
struct hashfile *hashfd(int fd, const char *name)
{
/*
* Since we are not going to use a progress meter to
* measure the rate of data passing through this hashfile,
* use a larger buffer size to reduce fsync() calls.
*/
return hashfd_internal(fd, name, NULL, 128 * 1024);
}
struct hashfile *hashfd_throughput(int fd, const char *name, struct progress *tp)
{
/*
* Since we are expecting to report progress of the
* write into this hashfile, use a smaller buffer
* size so the progress indicators arrive at a more
* frequent rate.
*/
return hashfd_internal(fd, name, tp, 8 * 1024);
}
void hashfile_checkpoint(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
{
hashflush(f);
checkpoint->offset = f->total;
the_hash_algo->clone_fn(&checkpoint->ctx, &f->ctx);
}
int hashfile_truncate(struct hashfile *f, struct hashfile_checkpoint *checkpoint)
{
off_t offset = checkpoint->offset;
if (ftruncate(f->fd, offset) ||
lseek(f->fd, offset, SEEK_SET) != offset)
return -1;
f->total = offset;
f->ctx = checkpoint->ctx;
f->offset = 0; /* hashflush() was called in checkpoint */
return 0;
}
void crc32_begin(struct hashfile *f)
{
f->crc32 = crc32(0, NULL, 0);
f->do_crc = 1;
}
uint32_t crc32_end(struct hashfile *f)
{
f->do_crc = 0;
return f->crc32;
}
int hashfile_checksum_valid(const unsigned char *data, size_t total_len)
{
unsigned char got[GIT_MAX_RAWSZ];
git_hash_ctx ctx;
size_t data_len = total_len - the_hash_algo->rawsz;
if (total_len < the_hash_algo->rawsz)
return 0; /* say "too short"? */
the_hash_algo->init_fn(&ctx);
the_hash_algo->update_fn(&ctx, data, data_len);
the_hash_algo->final_fn(got, &ctx);
return hasheq(got, data + data_len);
}