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samba-mirror/source3/modules/onefs_shadow_copy.c
2011-03-30 01:13:08 +02:00

784 lines
18 KiB
C

/*
* Unix SMB/CIFS implementation.
*
* OneFS shadow copy implementation that utilizes the file system's native
* snapshot support. This file does all of the heavy lifting.
*
* Copyright (C) Dave Richards, 2007
* Copyright (C) Tim Prouty, 2009
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, see <http://www.gnu.org/licenses/>.
*/
#include "smbd/smbd.h"
#include <ifs/ifs_syscalls.h>
#include <sys/types.h>
#include <sys/isi_enc.h>
#include <sys/module.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/time.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <search.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "onefs_shadow_copy.h"
/* Copied from ../include/proto.h */
void become_root(void);
void unbecome_root(void);
#define SNAPSHOT_DIRECTORY ".snapshot"
#define MAX_VERSIONS 64
/**
* A snapshot object.
*
* During snapshot enumeration, snapshots are represented by snapshot objects
* and are stored in a snapshot set. The snapshot object represents one
* snapshot within the set. An important thing to note about the set is that
* the key of the snapshot object is the tv_sec component of the is_time
* member. What this means is that we only store one snapshot for each
* second. If multiple snapshots were created within the same second, we'll
* keep the earliest one and ignore the rest. Thus, not all snapshots are
* necessarily retained.
*/
struct osc_snapshot {
char * is_name;
struct timespec is_time;
struct osc_snapshot * is_next;
};
/**
* A snapshot context object.
*
* Snapshot contexts are used to pass information throughout the snapshot
* enumeration routines. As a result, snapshot contexts are stored on the
* stack and are both created and destroyed within a single API function.
*/
struct osc_snapshot_ctx {
void * osc_set;
struct timespec osc_mtime;
};
/**
* A directory context.
*
* Directory contexts are the underlying data structured used to enumerate
* snapshot versions. An opendir()-, readdir()- and closedir()-like interface
* is provided that utilizes directory contexts. At the API level, directory
* contexts are passed around as void pointers. Directory contexts are
* allocated on the heap and their lifetime is dictated by the calling
* routine.
*/
struct osc_directory_ctx {
size_t idc_pos;
size_t idc_len;
size_t idc_size;
char ** idc_version;
};
/**
* Return a file descriptor to the STF names directory.
*
* Opens the STF names directory and returns a file descriptor to it.
* Subsequent calls return the same value (avoiding the need to re-open the
* directory repeatedly). Caveat caller: don't close the file descriptor or
* you will be shot!
*/
static int
osc_get_names_directory_fd(void)
{
static int fd = -1;
if (fd == -1) {
become_root();
fd = pctl2_lin_open(STF_NAMES_LIN, HEAD_SNAPID, O_RDONLY);
unbecome_root();
}
return fd;
}
/**
* Compare two time values.
*
* Accepts two struct timespecs and compares the tv_sec components of these
* values. It returns -1 if the first value preceeds the second, 0 if they
* are equal and +1 if the first values succeeds the second.
*/
static int
osc_time_compare(const struct timespec *tsp1, const struct timespec *tsp2)
{
return (tsp1->tv_sec < tsp2->tv_sec) ? -1 :
(tsp1->tv_sec > tsp2->tv_sec) ? +1 : 0;
}
/**
* Compare two timespec values.
*
* Compares two timespec values. It returns -1 if the first value preceeds
* the second, 0 if they are equal and +1 if the first values succeeds the
* second.
*/
static int
osc_timespec_compare(const struct timespec *tsp1, const struct timespec *tsp2)
{
return (tsp1->tv_sec < tsp2->tv_sec) ? -1 :
(tsp1->tv_sec > tsp2->tv_sec) ? +1 :
(tsp1->tv_nsec < tsp2->tv_nsec) ? -1 :
(tsp1->tv_nsec > tsp2->tv_nsec) ? +1 : 0;
}
/**
* Determine whether a timespec value is zero.
*
* Return 1 if the struct timespec provided is zero and 0 otherwise.
*/
static int
osc_timespec_is_zero(const struct timespec *tsp)
{
return (tsp->tv_sec == 0) &&
(tsp->tv_nsec == 0);
}
/**
* Create a snapshot object.
*
* Allocates and initializes a new snapshot object. In addition to allocating
* space for the snapshot object itself, space is allocated for the snapshot
* name. Both the name and time are then copied to the new object.
*/
static struct osc_snapshot *
osc_snapshot_create(const char *name, const struct timespec *tsp)
{
struct osc_snapshot *isp;
isp = malloc(sizeof *isp);
if (isp == NULL)
goto out;
isp->is_name = malloc(strlen(name) + 1);
if (isp->is_name == NULL) {
free(isp);
isp = NULL;
goto out;
}
strcpy(isp->is_name, name);
isp->is_time = *tsp;
isp->is_next = NULL;
out:
return isp;
}
/**
* Destroy a snapshot object.
*
* Frees both the name and the snapshot object itself. Appropriate NULL
* checking is performed because counting on free to do so is immoral.
*/
static void
osc_snapshot_destroy(struct osc_snapshot *isp)
{
if (isp != NULL) {
if (isp->is_name != NULL)
free(isp->is_name);
free(isp);
}
}
/**
* Destroy all snapshots in the snapshot list.
*
* Calls osc_snapshot_destroy() on each snapshot in the list.
*/
static void
osc_snapshot_destroy_list(struct osc_snapshot *isp)
{
struct osc_snapshot *tmp;
while (isp != NULL) {
tmp = isp;
isp = isp->is_next;
osc_snapshot_destroy(tmp);
}
}
/**
* Compare two snapshot objects.
*
* Compare two snapshot objects. It is really just a wrapper for
* osc_time_compare(), which compare the time value of the two snapshots.
* N.B. time value in this context refers only to the tv_sec component.
*/
static int
osc_snapshot_compare(const void *vp1, const void *vp2)
{
const struct osc_snapshot *isp1 = vp1;
const struct osc_snapshot *isp2 = vp2;
return -osc_time_compare(&isp1->is_time, &isp2->is_time);
}
/**
* Insert a snapshot into the snapshot set.
*
* Inserts a new snapshot into the snapshot set. The key for snapshots is
* their creation time (it's actually the seconds portion of the creation
* time). If a duplicate snapshot is found in the set, the new snapshot is
* added to a linked list of snapshots for that second.
*/
static void
osc_snapshot_insert(struct osc_snapshot_ctx *oscp, const char *name,
const struct timespec *tsp, int *errorp)
{
struct osc_snapshot *isp1;
struct osc_snapshot **ispp;
isp1 = osc_snapshot_create(name, tsp);
if (isp1 == NULL) {
*errorp = 1;
return;
}
ispp = tsearch(isp1, &oscp->osc_set, osc_snapshot_compare);
if (ispp != NULL) {
struct osc_snapshot *isp2 = *ispp;
/* If this is the only snapshot for this second, we're done. */
if (isp2 == isp1)
return;
/* Collision: add the new snapshot to the list. */
isp1->is_next = isp2->is_next;
isp2->is_next = isp1;
} else
*errorp = 1;
}
/**
* Process the next snapshot.
*
* Called for (almost) every entry in a .snapshot directory, ("." and ".." are
* ignored in osc_process_snapshot_directory()). All other entries are passed
* to osc_process_snapshot(), however. These entries can fall into one of two
* categories: snapshot names and snapshot aliases. We only care about
* snapshot names (as aliases are just redundant entries). Once it verifies
* that name represents a valid snapshot name, it calls fstat() to get the
* creation time of the snapshot and then calls osc_snapshot_insert() to add
* this entry to the snapshot set.
*/
static void
osc_process_snapshot(struct osc_snapshot_ctx *oscp, const char *name,
int *errorp)
{
int fd;
struct stf_stat stf_stat;
struct stat stbuf;
fd = osc_get_names_directory_fd();
if (fd == -1)
goto out;
fd = enc_openat(fd, name, ENC_DEFAULT, O_RDONLY);
if (fd == -1)
goto out;
memset(&stf_stat, 0, sizeof stf_stat);
if (ifs_snap_stat(fd, &stf_stat) == -1)
goto out;
if (stf_stat.sf_type != SF_STF)
goto out;
if (fstat(fd, &stbuf) == -1)
goto out;
osc_snapshot_insert(oscp, name, &stbuf.st_birthtimespec, errorp);
out:
if (fd != -1)
close(fd);
}
/**
* Process a snapshot directory.
*
* Opens the snapshot directory and calls osc_process_snapshot() for each
* entry. (Well ok, "." and ".." are ignored.) The goal here is to add all
* snapshots in the directory to the snapshot set.
*/
static void
osc_process_snapshot_directory(struct osc_snapshot_ctx *oscp, int *errorp)
{
int fd;
struct stat stbuf;
DIR *dirp;
struct dirent *dp;
fd = osc_get_names_directory_fd();
if (fd == -1)
goto out;
if (fstat(fd, &stbuf) == -1)
goto out;
dirp = opendir(SNAPSHOT_DIRECTORY);
if (dirp == NULL)
goto out;
for (;;) {
dp = readdir(dirp);
if (dp == NULL)
break;
if (dp->d_name[0] == '.' && (dp->d_name[1] == '\0' ||
(dp->d_name[1] == '.' && dp->d_name[2] == '\0')))
continue;
osc_process_snapshot(oscp, dp->d_name, errorp);
if (*errorp)
break;
}
closedir(dirp);
if (!*errorp)
oscp->osc_mtime = stbuf.st_mtimespec;
out:
return;
}
/**
* Initialize a snapshot context object.
*
* Clears all members of the context object.
*/
static void
osc_snapshot_ctx_init(struct osc_snapshot_ctx *oscp)
{
memset(oscp, 0, sizeof *oscp);
}
/**
* Desoy a snapshot context object.
*
* Frees all snapshots associated with the snapshot context and then calls
* osc_snapshot_ctx_init() to re-initialize the context object.
*/
static void
osc_snapshot_ctx_clean(struct osc_snapshot_ctx *oscp)
{
struct osc_snapshot *tmp;
while (oscp->osc_set != NULL) {
tmp = *(void **)oscp->osc_set;
tdelete(tmp, &oscp->osc_set, osc_snapshot_compare);
osc_snapshot_destroy_list(tmp);
}
osc_snapshot_ctx_init(oscp);
}
/**
* Return the "global" snapshot context.
*
* We maintain a single open snapshot context. Return a pointer to it.
*/
static struct osc_snapshot_ctx *
osc_get_snapshot_ctx(void)
{
static struct osc_snapshot_ctx osc = { 0, { 0, 0 } };
return &osc;
}
/**
* Determine whether a snapshot context is still valid.
*
* "Valid" in this context means "reusable". We can re-use a previous
* snapshot context iff we successfully built a previous snapshot context
* and no snapshots have been created or deleted since we did so.
* A "names" directory exists within our snapshot
* implementation in which all snapshot names are entered. Each time a
* snapshot is created or deleted, an entry must be added or removed.
* When this happens the modification time on the "names" directory
* changes. Therefore, a snapshot context is valid iff the context
* pointer is non-NULL, the cached modification time is non-zero
* (zero means uninitialized), and the modification time of the "names"
* directory matches the cached value.
*/
static int
osc_snapshot_ctx_is_valid(struct osc_snapshot_ctx *oscp)
{
int fd;
struct stat stbuf;
if (oscp == NULL)
return 0;
if (osc_timespec_is_zero(&oscp->osc_mtime))
return 0;
fd = osc_get_names_directory_fd();
if (fd == -1)
return 0;
if (fstat(fd, &stbuf) == -1)
return 0;
if (osc_timespec_compare(&oscp->osc_mtime, &stbuf.st_mtimespec) != 0)
return 0;
return 1;
}
/**
* Create and initialize a directory context.
*
* Allocates a directory context from the heap and initializes it.
*/
static struct osc_directory_ctx *
osc_directory_ctx_create(void)
{
struct osc_directory_ctx *idcp;
idcp = malloc(sizeof *idcp);
if (idcp != NULL)
memset(idcp, 0, sizeof *idcp);
return idcp;
}
/**
* Destroy a directory context.
*
* Frees any versions associated with the directory context and then frees the
* context itself.
*/
static void
osc_directory_ctx_destroy(struct osc_directory_ctx *idcp)
{
int i;
if (idcp == NULL)
return;
for (i = 0; i < idcp->idc_len; i++)
free(idcp->idc_version[i]);
free(idcp);
}
/**
* Expand the size of a directory context's version list.
*
* If osc_directory_ctx_append_version() detects that the version list is too
* small to accomodate a new version string, it called
* osc_directory_ctx_expand_version_list() to expand the version list.
*/
static void
osc_directory_ctx_expand_version_list(struct osc_snapshot_ctx *oscp,
struct osc_directory_ctx *idcp, int *errorp)
{
size_t size;
char **cpp;
size = idcp->idc_size * 2 ?: 1;
cpp = realloc(idcp->idc_version, size * sizeof (char *));
if (cpp == NULL) {
*errorp = 1;
return;
}
idcp->idc_size = size;
idcp->idc_version = cpp;
}
/**
* Append a new version to a directory context.
*
* Appends a snapshot version to the
* directory context's version list.
*/
static void
osc_directory_ctx_append_version(struct osc_snapshot_ctx *oscp,
struct osc_directory_ctx *idcp, const struct timespec *tsp, int *errorp)
{
char *cp;
struct tm *tmp;
char text[64];
if (idcp->idc_len >= MAX_VERSIONS)
return;
if (idcp->idc_len >= idcp->idc_size) {
osc_directory_ctx_expand_version_list(oscp, idcp, errorp);
if (*errorp)
return;
}
tmp = gmtime(&tsp->tv_sec);
if (tmp == NULL) {
*errorp = 1;
return;
}
snprintf(text, sizeof text,
"@GMT-%04u.%02u.%02u-%02u.%02u.%02u",
tmp->tm_year + 1900,
tmp->tm_mon + 1,
tmp->tm_mday,
tmp->tm_hour,
tmp->tm_min,
tmp->tm_sec);
cp = malloc(strlen(text) + 1);
if (cp == NULL) {
*errorp = 1;
return;
}
strcpy(cp, text);
idcp->idc_version[idcp->idc_len++] = cp;
}
/**
* Make a directory context from a snapshot context.
*
* Once a snapshot context has been completely filled-in,
* osc_make_directory_ctx() is used to build a directory context from it. The
* idea here is to create version for each snapshot in the snapshot set.
*/
static void
osc_make_directory_ctx(struct osc_snapshot_ctx *oscp,
struct osc_directory_ctx *idcp, int *errorp)
{
static void
walk(const void *vp, VISIT v, int level)
{
const struct osc_snapshot *isp;
if ((v != postorder && v != leaf) || *errorp)
return;
isp = *(const struct osc_snapshot **)(u_long)vp;
osc_directory_ctx_append_version(oscp, idcp, &isp->is_time,
errorp);
}
twalk(oscp->osc_set, walk);
}
/**
* Open a version directory.
*
* Opens a version directory. What this really means is that
* osc_version_opendir() returns a handle to a directory context, which can be
* used to retrieve version strings.
*/
void *
osc_version_opendir(void)
{
int error = 0;
struct osc_directory_ctx *idcp;
struct osc_snapshot_ctx *oscp;
idcp = osc_directory_ctx_create();
if (idcp == NULL)
goto error_out;
oscp = osc_get_snapshot_ctx();
if (!osc_snapshot_ctx_is_valid(oscp)) {
osc_snapshot_ctx_clean(oscp);
osc_process_snapshot_directory(oscp, &error);
if (error)
goto error_out;
}
osc_make_directory_ctx(oscp, idcp, &error);
if (error)
goto error_out;
goto out;
error_out:
if (idcp != NULL) {
osc_directory_ctx_destroy(idcp);
idcp = NULL;
}
out:
return (void *)idcp;
}
/**
* Read the next version directory entry.
*
* Returns the name of the next version in the version directory, or NULL if
* we're at the end of the directory. What this really does is return the
* next version from the version list stored in the directory context.
*/
char *
osc_version_readdir(void *vp)
{
struct osc_directory_ctx *idcp = vp;
if (idcp == NULL)
return NULL;
if (idcp->idc_pos >= idcp->idc_len)
return NULL;
return idcp->idc_version[idcp->idc_pos++];
}
/**
* Close the version directory.
*
* Destroys the underlying directory context.
*/
void
osc_version_closedir(void *vp)
{
struct osc_directory_ctx *idcp = vp;
if (idcp != NULL)
osc_directory_ctx_destroy(idcp);
}
/**
* Canonicalize a path.
*
* Converts paths of the form @GMT-.. to paths of the form ../.snapshot/..
* It's not the prettiest routine I've ever written, but what the heck?
*/
char *
osc_canonicalize_path(const char *path, char *snap_component)
{
int error = 0;
struct osc_snapshot_ctx *oscp;
struct tm tm;
int n;
struct osc_snapshot is;
struct osc_snapshot **ispp;
struct osc_snapshot *isp;
char *cpath = NULL;
char *cpath2 = NULL;
const char *snap_component_orig = snap_component;
struct stat sb;
oscp = osc_get_snapshot_ctx();
if (!osc_snapshot_ctx_is_valid(oscp)) {
osc_snapshot_ctx_clean(oscp);
osc_process_snapshot_directory(oscp, &error);
if (error)
goto out;
}
memset(&tm, 0, sizeof tm);
n = sscanf(snap_component,
"@GMT-%4u.%2u.%2u-%2u.%2u.%2u",
&tm.tm_year,
&tm.tm_mon,
&tm.tm_mday,
&tm.tm_hour,
&tm.tm_min,
&tm.tm_sec);
if (n != 6)
goto out;
tm.tm_year -= 1900;
tm.tm_mon -= 1;
is.is_name = NULL;
is.is_time.tv_sec = timegm(&tm);
is.is_time.tv_nsec = 0;
ispp = tfind(&is, &oscp->osc_set, osc_snapshot_compare);
if (ispp == NULL)
goto out;
isp = *ispp;
/* Determine the path after "@GMT-..." */
while (*snap_component != '/' && *snap_component != '\0')
snap_component++;
while (*snap_component == '/')
snap_component++;
cpath = malloc(strlen(SNAPSHOT_DIRECTORY) + strlen(isp->is_name) +
strlen(path) + 3);
if (cpath == NULL)
goto out;
/*
* Use the first snapshot that has a successful stat for the requested
* path.
*/
while (true) {
sprintf(cpath, "%s/%s", SNAPSHOT_DIRECTORY, isp->is_name);
/* Append path before "@GMT-..." */
if (snap_component_orig != path) {
strcat(cpath, "/");
strncat(cpath, path, snap_component_orig - path);
}
/* Append path after "@GMT-..." */
if (*snap_component != '\0') {
strcat(cpath, "/");
strcat(cpath, snap_component);
}
/* If there is a valid snapshot for this file, we're done. */
if (stat(cpath, &sb) == 0)
break;
/* Try the next snapshot. If this was the last one, give up. */
isp = isp->is_next;
if (isp == NULL)
break;
/* If the realloc fails, give up. */
cpath2 = realloc(cpath, strlen(SNAPSHOT_DIRECTORY) +
strlen(isp->is_name) + strlen(path) + 3);
if (cpath2 == NULL)
break;
cpath = cpath2;
}
out:
return cpath;
}