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Systemd/src/import/export-raw.c
Lennart Poettering adc6f43b14 copy: don't synthesize a 'user.crtime_usec' xattr on copy unless explicitly requested 
Previously, when we'd copy an individual file we'd synthesize a
user.crtime_usec xattr with the source's creation time if we can
determine it. As the creation/birth time was until recently not
queriable form userspace this effectively just propagated the same xattr
on the source to the same xattr on the destination. However, current
kernels now allow to query the birthtime using statx() and we do make
use of that now. Which means that suddenly we started synthesizing these
xattrs much more regularly.

Doing this actually does make sense, but only in very few cases:
not for the typical regular files we copy, but certainly when dealing
with disk images. Hence, let's keep this kind of propagation, but let's
make it a flag and default to off. Then turn it on whenever we deal with
disk images, and leave it off otherwise.

This is particularly relevant as overlayfs combining a real fs, and a
tmpfs on top will result in EOPNOTSUPP when it is attempted to open a
file with xattrs for writing, as tmpfs does not support xattrs, and
hence the copy-up cannot work. Hence, let's avoid synthesizing this
needlessly, to increase compat with overlayfs.
2019-03-01 14:11:07 +01:00

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/* SPDX-License-Identifier: LGPL-2.1+ */
#include <sys/sendfile.h>
/* When we include libgen.h because we need dirname() we immediately
* undefine basename() since libgen.h defines it as a macro to the POSIX
* version which is really broken. We prefer GNU basename(). */
#include <libgen.h>
#undef basename
#include "sd-daemon.h"
#include "alloc-util.h"
#include "btrfs-util.h"
#include "copy.h"
#include "export-raw.h"
#include "fd-util.h"
#include "fs-util.h"
#include "import-common.h"
#include "missing.h"
#include "ratelimit.h"
#include "stat-util.h"
#include "string-util.h"
#include "tmpfile-util.h"
#include "util.h"
#define COPY_BUFFER_SIZE (16*1024)
struct RawExport {
sd_event *event;
RawExportFinished on_finished;
void *userdata;
char *path;
int input_fd;
int output_fd;
ImportCompress compress;
sd_event_source *output_event_source;
void *buffer;
size_t buffer_size;
size_t buffer_allocated;
uint64_t written_compressed;
uint64_t written_uncompressed;
unsigned last_percent;
RateLimit progress_rate_limit;
struct stat st;
bool eof;
bool tried_reflink;
bool tried_sendfile;
};
RawExport *raw_export_unref(RawExport *e) {
if (!e)
return NULL;
sd_event_source_unref(e->output_event_source);
import_compress_free(&e->compress);
sd_event_unref(e->event);
safe_close(e->input_fd);
free(e->buffer);
free(e->path);
return mfree(e);
}
int raw_export_new(
RawExport **ret,
sd_event *event,
RawExportFinished on_finished,
void *userdata) {
_cleanup_(raw_export_unrefp) RawExport *e = NULL;
int r;
assert(ret);
e = new(RawExport, 1);
if (!e)
return -ENOMEM;
*e = (RawExport) {
.output_fd = -1,
.input_fd = -1,
.on_finished = on_finished,
.userdata = userdata,
.last_percent = (unsigned) -1,
};
RATELIMIT_INIT(e->progress_rate_limit, 100 * USEC_PER_MSEC, 1);
if (event)
e->event = sd_event_ref(event);
else {
r = sd_event_default(&e->event);
if (r < 0)
return r;
}
*ret = TAKE_PTR(e);
return 0;
}
static void raw_export_report_progress(RawExport *e) {
unsigned percent;
assert(e);
if (e->written_uncompressed >= (uint64_t) e->st.st_size)
percent = 100;
else
percent = (unsigned) ((e->written_uncompressed * UINT64_C(100)) / (uint64_t) e->st.st_size);
if (percent == e->last_percent)
return;
if (!ratelimit_below(&e->progress_rate_limit))
return;
sd_notifyf(false, "X_IMPORT_PROGRESS=%u", percent);
log_info("Exported %u%%.", percent);
e->last_percent = percent;
}
static int raw_export_process(RawExport *e) {
ssize_t l;
int r;
assert(e);
if (!e->tried_reflink && e->compress.type == IMPORT_COMPRESS_UNCOMPRESSED) {
/* If we shall take an uncompressed snapshot we can
* reflink source to destination directly. Let's see
* if this works. */
r = btrfs_reflink(e->input_fd, e->output_fd);
if (r >= 0) {
r = 0;
goto finish;
}
e->tried_reflink = true;
}
if (!e->tried_sendfile && e->compress.type == IMPORT_COMPRESS_UNCOMPRESSED) {
l = sendfile(e->output_fd, e->input_fd, NULL, COPY_BUFFER_SIZE);
if (l < 0) {
if (errno == EAGAIN)
return 0;
e->tried_sendfile = true;
} else if (l == 0) {
r = 0;
goto finish;
} else {
e->written_uncompressed += l;
e->written_compressed += l;
raw_export_report_progress(e);
return 0;
}
}
while (e->buffer_size <= 0) {
uint8_t input[COPY_BUFFER_SIZE];
if (e->eof) {
r = 0;
goto finish;
}
l = read(e->input_fd, input, sizeof(input));
if (l < 0) {
r = log_error_errno(errno, "Failed to read raw file: %m");
goto finish;
}
if (l == 0) {
e->eof = true;
r = import_compress_finish(&e->compress, &e->buffer, &e->buffer_size, &e->buffer_allocated);
} else {
e->written_uncompressed += l;
r = import_compress(&e->compress, input, l, &e->buffer, &e->buffer_size, &e->buffer_allocated);
}
if (r < 0) {
r = log_error_errno(r, "Failed to encode: %m");
goto finish;
}
}
l = write(e->output_fd, e->buffer, e->buffer_size);
if (l < 0) {
if (errno == EAGAIN)
return 0;
r = log_error_errno(errno, "Failed to write output file: %m");
goto finish;
}
assert((size_t) l <= e->buffer_size);
memmove(e->buffer, (uint8_t*) e->buffer + l, e->buffer_size - l);
e->buffer_size -= l;
e->written_compressed += l;
raw_export_report_progress(e);
return 0;
finish:
if (r >= 0) {
(void) copy_times(e->input_fd, e->output_fd, COPY_CRTIME);
(void) copy_xattr(e->input_fd, e->output_fd);
}
if (e->on_finished)
e->on_finished(e, r, e->userdata);
else
sd_event_exit(e->event, r);
return 0;
}
static int raw_export_on_output(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
RawExport *i = userdata;
return raw_export_process(i);
}
static int raw_export_on_defer(sd_event_source *s, void *userdata) {
RawExport *i = userdata;
return raw_export_process(i);
}
static int reflink_snapshot(int fd, const char *path) {
int new_fd, r;
new_fd = open_parent(path, O_TMPFILE|O_CLOEXEC|O_RDWR, 0600);
if (new_fd < 0) {
_cleanup_free_ char *t = NULL;
r = tempfn_random(path, NULL, &t);
if (r < 0)
return r;
new_fd = open(t, O_CLOEXEC|O_CREAT|O_NOCTTY|O_RDWR, 0600);
if (new_fd < 0)
return -errno;
(void) unlink(t);
}
r = btrfs_reflink(fd, new_fd);
if (r < 0) {
safe_close(new_fd);
return r;
}
return new_fd;
}
int raw_export_start(RawExport *e, const char *path, int fd, ImportCompressType compress) {
_cleanup_close_ int sfd = -1, tfd = -1;
int r;
assert(e);
assert(path);
assert(fd >= 0);
assert(compress < _IMPORT_COMPRESS_TYPE_MAX);
assert(compress != IMPORT_COMPRESS_UNKNOWN);
if (e->output_fd >= 0)
return -EBUSY;
r = fd_nonblock(fd, true);
if (r < 0)
return r;
r = free_and_strdup(&e->path, path);
if (r < 0)
return r;
sfd = open(path, O_RDONLY|O_CLOEXEC|O_NOCTTY);
if (sfd < 0)
return -errno;
if (fstat(sfd, &e->st) < 0)
return -errno;
r = stat_verify_regular(&e->st);
if (r < 0)
return r;
/* Try to take a reflink snapshot of the file, if we can t make the export atomic */
tfd = reflink_snapshot(sfd, path);
if (tfd >= 0)
e->input_fd = TAKE_FD(tfd);
else
e->input_fd = TAKE_FD(sfd);
r = import_compress_init(&e->compress, compress);
if (r < 0)
return r;
r = sd_event_add_io(e->event, &e->output_event_source, fd, EPOLLOUT, raw_export_on_output, e);
if (r == -EPERM) {
r = sd_event_add_defer(e->event, &e->output_event_source, raw_export_on_defer, e);
if (r < 0)
return r;
r = sd_event_source_set_enabled(e->output_event_source, SD_EVENT_ON);
}
if (r < 0)
return r;
e->output_fd = fd;
return r;
}
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