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/*-
* Copyright (c) 2014-2016 MongoDB, Inc.
* Copyright (c) 2008-2014 WiredTiger, Inc.
* All rights reserved.
*
* See the file LICENSE for redistribution information.
*/
#include "wt_internal.h"
/*
* __wt_filename --
* Build a file name in a scratch buffer, automatically calculate the
* length of the file name.
*/
int
__wt_filename(WT_SESSION_IMPL *session, const char *name, char **path)
{
return (__wt_nfilename(session, name, strlen(name), path));
}
/*
* __wt_nfilename --
* Build a file name in a scratch buffer. If the name is already an
* absolute path duplicate it, otherwise generate a path relative to the
* connection home directory.
*/
int
__wt_nfilename(
WT_SESSION_IMPL *session, const char *name, size_t namelen, char **path)
{
size_t len;
char *buf;
*path = NULL;
/*
* Needs to work with a NULL session handle - since this is called via
* the exists API which is used by the test utilities.
*/
if (session == NULL || __wt_absolute_path(name))
WT_RET(__wt_strndup(session, name, namelen, path));
else {
len = strlen(S2C(session)->home) + 1 + namelen + 1;
WT_RET(__wt_calloc(session, 1, len, &buf));
snprintf(buf, len, "%s%s%.*s", S2C(session)->home,
__wt_path_separator(), (int)namelen, name);
*path = buf;
}
return (0);
}
/*
* __wt_remove_if_exists --
* Remove a file if it exists.
*/
int
__wt_remove_if_exists(WT_SESSION_IMPL *session, const char *name)
{
bool exist;
WT_RET(__wt_fs_exist(session, name, &exist));
if (exist)
WT_RET(__wt_fs_remove(session, name));
return (0);
}
/*
* __wt_rename_and_sync_directory --
* Rename a file and sync the enclosing directory.
*/
int
__wt_rename_and_sync_directory(
WT_SESSION_IMPL *session, const char *from, const char *to)
{
const char *fp, *tp;
bool same_directory;
/* Rename the source file to the target. */
WT_RET(__wt_fs_rename(session, from, to));
/*
* Flush the backing directory to guarantee the rename. My reading of
* POSIX 1003.1 is there's no guarantee flushing only one of the from
* or to directories, or flushing a common parent, is sufficient, and
* even if POSIX were to make that guarantee, existing filesystems are
* known to not provide the guarantee or only provide the guarantee
* with specific mount options. Flush both of the from/to directories
* until it's a performance problem.
*/
WT_RET(__wt_fs_directory_sync(session, from));
/*
* In almost all cases, we're going to be renaming files in the same
* directory, we can at least fast-path that.
*/
fp = strrchr(from, '/');
tp = strrchr(to, '/');
same_directory = (fp == NULL && tp == NULL) ||
(fp != NULL && tp != NULL &&
fp - from == tp - to && memcmp(from, to, (size_t)(fp - from)) == 0);
return (same_directory ? 0 : __wt_fs_directory_sync(session, to));
}
/*
* __wt_copy_and_sync --
* Copy a file safely; here to support the wt utility.
*/
int
__wt_copy_and_sync(WT_SESSION *wt_session, const char *from, const char *to)
{
WT_DECL_ITEM(tmp);
WT_DECL_RET;
WT_FH *ffh, *tfh;
WT_SESSION_IMPL *session;
wt_off_t n, offset, size;
char *buf;
session = (WT_SESSION_IMPL *)wt_session;
ffh = tfh = NULL;
buf = NULL;
/*
* Remove the target file if it exists, then create a temporary file,
* copy the original into it and rename it into place. I don't think
* its necessary to remove the file, or create a copy and do a rename,
* it's likely safe to overwrite the backup file directly. I'm doing
* the remove and rename to insulate us from errors in other programs
* that might not detect a corrupted backup file; it's cheap insurance
* in a path where undetected failure is very bad.
*/
WT_ERR(__wt_scr_alloc(session, 0, &tmp));
WT_ERR(__wt_buf_fmt(session, tmp, "%s.copy", to));
WT_ERR(__wt_remove_if_exists(session, to));
WT_ERR(__wt_remove_if_exists(session, tmp->data));
/* Open the from and temporary file handles. */
WT_ERR(__wt_open(session, from, WT_OPEN_FILE_TYPE_REGULAR, 0, &ffh));
WT_ERR(__wt_open(session, tmp->data, WT_OPEN_FILE_TYPE_REGULAR,
WT_OPEN_CREATE | WT_OPEN_EXCLUSIVE, &tfh));
/*
* Allocate a copy buffer. Don't use a scratch buffer, this thing is
* big, and we don't want it hanging around.
*/
#define WT_BACKUP_COPY_SIZE (128 * 1024)
WT_ERR(__wt_malloc(session, WT_BACKUP_COPY_SIZE, &buf));
/* Get the file's size, then copy the bytes. */
WT_ERR(__wt_filesize(session, ffh, &size));
for (offset = 0; size > 0; size -= n, offset += n) {
n = WT_MIN(size, WT_BACKUP_COPY_SIZE);
WT_ERR(__wt_read(session, ffh, offset, (size_t)n, buf));
WT_ERR(__wt_write(session, tfh, offset, (size_t)n, buf));
}
/* Close the from handle, then swap the temporary file into place. */
WT_ERR(__wt_close(session, &ffh));
WT_ERR(__wt_fsync(session, tfh, true));
WT_ERR(__wt_close(session, &tfh));
ret = __wt_rename_and_sync_directory(session, tmp->data, to);
err: WT_TRET(__wt_close(session, &ffh));
WT_TRET(__wt_close(session, &tfh));
__wt_free(session, buf);
__wt_scr_free(session, &tmp);
return (ret);
}
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