path: root/lib/tdb2/tdb1_io.c

 /*
   Unix SMB/CIFS implementation.

   trivial database library

   Copyright (C) Andrew Tridgell              1999-2005
   Copyright (C) Paul `Rusty' Russell		   2000
   Copyright (C) Jeremy Allison			   2000-2003

     ** NOTE! The following LGPL license applies to the tdb
     ** library. This does NOT imply that all of Samba is released
     ** under the LGPL

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 3 of the License, or (at your option) any later version.

   This library 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
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/


#include "tdb1_private.h"
#ifndef MAX
#define MAX(a,b) ((a) > (b) ? (a) : (b))
#endif

/* check for an out of bounds access - if it is out of bounds then
   see if the database has been expanded by someone else and expand
   if necessary
   note that "len" is the minimum length needed for the db
*/
static int tdb1_oob(struct tdb_context *tdb, tdb1_off_t len, int probe)
{
	struct stat st;
	if (len <= tdb->file->map_size)
		return 0;
	if (tdb->flags & TDB_INTERNAL) {
		if (!probe) {
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"tdb1_oob len %d beyond internal malloc size %d",
						(int)len, (int)tdb->file->map_size);
		}
		return -1;
	}

	if (fstat(tdb->file->fd, &st) == -1) {
		tdb->last_error = TDB_ERR_IO;
		return -1;
	}

	if (st.st_size < (size_t)len) {
		if (!probe) {
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"tdb1_oob len %d beyond eof at %d",
						(int)len, (int)st.st_size);
		}
		return -1;
	}

	/* Unmap, update size, remap */
	if (tdb1_munmap(tdb) == -1) {
		tdb->last_error = TDB_ERR_IO;
		return -1;
	}
	tdb->file->map_size = st.st_size;
	tdb1_mmap(tdb);
	return 0;
}

/* write a lump of data at a specified offset */
static int tdb1_write(struct tdb_context *tdb, tdb1_off_t off,
		     const void *buf, tdb1_len_t len)
{
	if (len == 0) {
		return 0;
	}

	if ((tdb->flags & TDB_RDONLY) || tdb->tdb1.traverse_read) {
		tdb->last_error = TDB_ERR_RDONLY;
		return -1;
	}

	if (tdb->tdb1.io->tdb1_oob(tdb, off + len, 0) != 0)
		return -1;

	if (tdb->file->map_ptr) {
		memcpy(off + (char *)tdb->file->map_ptr, buf, len);
	} else {
		ssize_t written = pwrite(tdb->file->fd, buf, len, off);
		if ((written != (ssize_t)len) && (written != -1)) {
			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_WARNING,
				   "tdb1_write: wrote only "
				   "%d of %d bytes at %d, trying once more",
				   (int)written, len, off);
			written = pwrite(tdb->file->fd,
					 (const char *)buf+written,
					 len-written,
					 off+written);
		}
		if (written == -1) {
			/* Ensure ecode is set for log fn. */
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"tdb1_write failed at %d "
						"len=%d (%s)",
						off, len, strerror(errno));
			return -1;
		} else if (written != (ssize_t)len) {
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"tdb1_write: failed to "
						"write %d bytes at %d in two attempts",
						len, off);
			return -1;
		}
	}
	return 0;
}

/* Endian conversion: we only ever deal with 4 byte quantities */
void *tdb1_convert(void *buf, uint32_t size)
{
	uint32_t i, *p = (uint32_t *)buf;
	for (i = 0; i < size / 4; i++)
		p[i] = TDB1_BYTEREV(p[i]);
	return buf;
}


/* read a lump of data at a specified offset, maybe convert */
static int tdb1_read(struct tdb_context *tdb, tdb1_off_t off, void *buf,
		    tdb1_len_t len, int cv)
{
	if (tdb->tdb1.io->tdb1_oob(tdb, off + len, 0) != 0) {
		return -1;
	}

	if (tdb->file->map_ptr) {
		memcpy(buf, off + (char *)tdb->file->map_ptr, len);
	} else {
		ssize_t ret = pread(tdb->file->fd, buf, len, off);
		if (ret != (ssize_t)len) {
			/* Ensure ecode is set for log fn. */
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"tdb1_read failed at %d "
						"len=%d ret=%d (%s) map_size=%d",
						(int)off, (int)len, (int)ret,
						strerror(errno),
						(int)tdb->file->map_size);
			return -1;
		}
	}
	if (cv) {
		tdb1_convert(buf, len);
	}
	return 0;
}



/*
  do an unlocked scan of the hash table heads to find the next non-zero head. The value
  will then be confirmed with the lock held
*/
static void tdb1_next_hash_chain(struct tdb_context *tdb, uint32_t *chain)
{
	uint32_t h = *chain;
	if (tdb->file->map_ptr) {
		for (;h < tdb->tdb1.header.hash_size;h++) {
			if (0 != *(uint32_t *)(TDB1_HASH_TOP(h) + (unsigned char *)tdb->file->map_ptr)) {
				break;
			}
		}
	} else {
		uint32_t off=0;
		for (;h < tdb->tdb1.header.hash_size;h++) {
			if (tdb1_ofs_read(tdb, TDB1_HASH_TOP(h), &off) != 0 || off != 0) {
				break;
			}
		}
	}
	(*chain) = h;
}


int tdb1_munmap(struct tdb_context *tdb)
{
	if (tdb->flags & TDB_INTERNAL)
		return 0;

#if HAVE_MMAP
	if (tdb->file->map_ptr) {
		int ret;

		ret = munmap(tdb->file->map_ptr, tdb->file->map_size);
		if (ret != 0)
			return ret;
	}
#endif
	tdb->file->map_ptr = NULL;
	return 0;
}

void tdb1_mmap(struct tdb_context *tdb)
{
	if (tdb->flags & TDB_INTERNAL)
		return;

#if HAVE_MMAP
	if (!(tdb->flags & TDB_NOMMAP)) {
		int mmap_flags;
		if ((tdb->open_flags & O_ACCMODE) == O_RDONLY)
			mmap_flags = PROT_READ;
		else
			mmap_flags = PROT_READ | PROT_WRITE;

		tdb->file->map_ptr = mmap(NULL, tdb->file->map_size,
				    mmap_flags,
				    MAP_SHARED|MAP_FILE, tdb->file->fd, 0);

		/*
		 * NB. When mmap fails it returns MAP_FAILED *NOT* NULL !!!!
		 */

		if (tdb->file->map_ptr == MAP_FAILED) {
			tdb->file->map_ptr = NULL;
			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_WARNING,
				   "tdb1_mmap failed for size %d (%s)",
				   tdb->file->map_size, strerror(errno));
		}
	} else {
		tdb->file->map_ptr = NULL;
	}
#else
	tdb->file->map_ptr = NULL;
#endif
}

/* expand a file.  we prefer to use ftruncate, as that is what posix
  says to use for mmap expansion */
static int tdb1_expand_file(struct tdb_context *tdb, tdb1_off_t size, tdb1_off_t addition)
{
	char buf[8192];

	if ((tdb->flags & TDB_RDONLY) || tdb->tdb1.traverse_read) {
		tdb->last_error = TDB_ERR_RDONLY;
		return -1;
	}

	if (ftruncate(tdb->file->fd, size+addition) == -1) {
		char b = 0;
		ssize_t written = pwrite(tdb->file->fd, &b, 1,
					 (size+addition) - 1);
		if (written == 0) {
			/* try once more, potentially revealing errno */
			written = pwrite(tdb->file->fd, &b, 1,
					 (size+addition) - 1);
		}
		if (written == 0) {
			/* again - give up, guessing errno */
			errno = ENOSPC;
		}
		if (written != 1) {
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"expand_file to %d failed (%s)",
						size+addition,
						strerror(errno));
			return -1;
		}
	}

	/* now fill the file with something. This ensures that the
	   file isn't sparse, which would be very bad if we ran out of
	   disk. This must be done with write, not via mmap */
	memset(buf, TDB1_PAD_BYTE, sizeof(buf));
	while (addition) {
		size_t n = addition>sizeof(buf)?sizeof(buf):addition;
		ssize_t written = pwrite(tdb->file->fd, buf, n, size);
		if (written == 0) {
			/* prevent infinite loops: try _once_ more */
			written = pwrite(tdb->file->fd, buf, n, size);
		}
		if (written == 0) {
			/* give up, trying to provide a useful errno */
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"expand_file write "
						"returned 0 twice: giving up!");
			errno = ENOSPC;
			return -1;
		} else if (written == -1) {
			tdb->last_error = tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_ERROR,
						"expand_file write of "
						"%d bytes failed (%s)", (int)n,
						strerror(errno));
			return -1;
		} else if (written != n) {
			tdb_logerr(tdb, TDB_ERR_IO, TDB_LOG_WARNING,
				   "expand_file: wrote "
				   "only %d of %d bytes - retrying",
				   (int)written, (int)n);
		}
		addition -= written;
		size += written;
	}
	tdb->stats.expands++;
	return 0;
}


/* expand the database at least size bytes by expanding the underlying
   file and doing the mmap again if necessary */
int tdb1_expand(struct tdb_context *tdb, tdb1_off_t size)
{
	struct tdb1_record rec;
	tdb1_off_t offset, new_size, top_size, map_size;

	if (tdb1_lock(tdb, -1, F_WRLCK) == -1) {
		tdb_logerr(tdb, tdb->last_error, TDB_LOG_ERROR,
			   "lock failed in tdb1_expand");
		return -1;
	}

	/* must know about any previous expansions by another process */
	tdb->tdb1.io->tdb1_oob(tdb, tdb->file->map_size + 1, 1);

	/* limit size in order to avoid using up huge amounts of memory for
	 * in memory tdbs if an oddball huge record creeps in */
	if (size > 100 * 1024) {
		top_size = tdb->file->map_size + size * 2;
	} else {
		top_size = tdb->file->map_size + size * 100;
	}

	/* always make room for at least top_size more records, and at
	   least 25% more space. if the DB is smaller than 100MiB,
	   otherwise grow it by 10% only. */
	if (tdb->file->map_size > 100 * 1024 * 1024) {
		map_size = tdb->file->map_size * 1.10;
	} else {
		map_size = tdb->file->map_size * 1.25;
	}

	/* Round the database up to a multiple of the page size */
	new_size = MAX(top_size, map_size);
	size = TDB1_ALIGN(new_size, tdb->tdb1.page_size) - tdb->file->map_size;

	if (!(tdb->flags & TDB_INTERNAL))
		tdb1_munmap(tdb);

	/*
	 * We must ensure the file is unmapped before doing this
	 * to ensure consistency with systems like OpenBSD where
	 * writes and mmaps are not consistent.
	 */

	/* expand the file itself */
	if (!(tdb->flags & TDB_INTERNAL)) {
		if (tdb->tdb1.io->tdb1_expand_file(tdb, tdb->file->map_size, size) != 0)
			goto fail;
	}

	tdb->file->map_size += size;

	if (tdb->flags & TDB_INTERNAL) {
		char *new_map_ptr = (char *)realloc(tdb->file->map_ptr,
						    tdb->file->map_size);
		if (!new_map_ptr) {
			tdb->file->map_size -= size;
			goto fail;
		}
		tdb->file->map_ptr = new_map_ptr;
	} else {
		/*
		 * We must ensure the file is remapped before adding the space
		 * to ensure consistency with systems like OpenBSD where
		 * writes and mmaps are not consistent.
		 */

		/* We're ok if the mmap fails as we'll fallback to read/write */
		tdb1_mmap(tdb);
	}

	/* form a new freelist record */
	memset(&rec,'\0',sizeof(rec));
	rec.rec_len = size - sizeof(rec);

	/* link it into the free list */
	offset = tdb->file->map_size - size;
	if (tdb1_free(tdb, offset, &rec) == -1)
		goto fail;

	tdb1_unlock(tdb, -1, F_WRLCK);
	return 0;
 fail:
	tdb1_unlock(tdb, -1, F_WRLCK);
	return -1;
}

/* read/write a tdb1_off_t */
int tdb1_ofs_read(struct tdb_context *tdb, tdb1_off_t offset, tdb1_off_t *d)
{
	return tdb->tdb1.io->tdb1_read(tdb, offset, (char*)d, sizeof(*d), TDB1_DOCONV());
}

int tdb1_ofs_write(struct tdb_context *tdb, tdb1_off_t offset, tdb1_off_t *d)
{
	tdb1_off_t off = *d;
	return tdb->tdb1.io->tdb1_write(tdb, offset, TDB1_CONV(off), sizeof(*d));
}


/* read a lump of data, allocating the space for it */
unsigned char *tdb1_alloc_read(struct tdb_context *tdb, tdb1_off_t offset, tdb1_len_t len)
{
	unsigned char *buf;

	/* some systems don't like zero length malloc */

	if (!(buf = (unsigned char *)malloc(len ? len : 1))) {
		tdb->last_error = tdb_logerr(tdb, TDB_ERR_OOM, TDB_LOG_ERROR,
					     "tdb1_alloc_read malloc failed"
					     " len=%d (%s)",
					     len, strerror(errno));
		return NULL;
	}
	if (tdb->tdb1.io->tdb1_read(tdb, offset, buf, len, 0) == -1) {
		SAFE_FREE(buf);
		return NULL;
	}
	return buf;
}

/* Give a piece of tdb data to a parser */
enum TDB_ERROR tdb1_parse_data(struct tdb_context *tdb, TDB_DATA key,
			       tdb1_off_t offset, tdb1_len_t len,
			       enum TDB_ERROR (*parser)(TDB_DATA key,
							TDB_DATA data,
							void *private_data),
			       void *private_data)
{
	TDB_DATA data;
	enum TDB_ERROR result;

	data.dsize = len;

	if ((tdb->tdb1.transaction == NULL) && (tdb->file->map_ptr != NULL)) {
		/*
		 * Optimize by avoiding the malloc/memcpy/free, point the
		 * parser directly at the mmap area.
		 */
		if (tdb->tdb1.io->tdb1_oob(tdb, offset+len, 0) != 0) {
			return tdb->last_error;
		}
		data.dptr = offset + (unsigned char *)tdb->file->map_ptr;
		return parser(key, data, private_data);
	}

	if (!(data.dptr = tdb1_alloc_read(tdb, offset, len))) {
		return tdb->last_error;
	}

	result = parser(key, data, private_data);
	free(data.dptr);
	return result;
}

/* read/write a record */
int tdb1_rec_read(struct tdb_context *tdb, tdb1_off_t offset, struct tdb1_record *rec)
{
	if (tdb->tdb1.io->tdb1_read(tdb, offset, rec, sizeof(*rec),TDB1_DOCONV()) == -1)
		return -1;
	if (TDB1_BAD_MAGIC(rec)) {
		tdb->last_error = tdb_logerr(tdb, TDB_ERR_CORRUPT, TDB_LOG_ERROR,
					"tdb1_rec_read bad magic 0x%x at offset=%d",
					rec->magic, offset);
		return -1;
	}
	return tdb->tdb1.io->tdb1_oob(tdb, rec->next+sizeof(*rec), 0);
}

int tdb1_rec_write(struct tdb_context *tdb, tdb1_off_t offset, struct tdb1_record *rec)
{
	struct tdb1_record r = *rec;
	return tdb->tdb1.io->tdb1_write(tdb, offset, TDB1_CONV(r), sizeof(r));
}

static const struct tdb1_methods io1_methods = {
	tdb1_read,
	tdb1_write,
	tdb1_next_hash_chain,
	tdb1_oob,
	tdb1_expand_file,
};

/*
  initialise the default methods table
*/
void tdb1_io_init(struct tdb_context *tdb)
{
	tdb->tdb1.io = &io1_methods;
}

enum TDB_ERROR tdb1_probe_length(struct tdb_context *tdb)
{
	tdb->last_error = TDB_SUCCESS;
	tdb->tdb1.io->tdb1_oob(tdb, tdb->file->map_size + 1, true);
	return tdb->last_error;
}