minix/lib/libsffs/write.c

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/* This file contains file writing system call handlers.
*
* The entry points into this file are:
* do_write perform the WRITE file system call
* do_ftrunc perform the FTRUNC file system call
*
* Created:
* April 2009 (D.C. van Moolenbroek)
*/
#include "inc.h"
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static int write_file(struct inode *ino, u64_t *posp, size_t *countp,
cp_grant_id_t *grantp);
/*===========================================================================*
* write_file *
*===========================================================================*/
static int write_file(struct inode *ino, u64_t *posp, size_t *countp,
cp_grant_id_t *grantp)
{
/* Write data or zeroes to a file, depending on whether a valid pointer to
* a data grant was provided.
*/
u64_t pos;
size_t count, size;
vir_bytes off;
char *ptr;
int r, chunk;
assert(!IS_DIR(ino));
if ((r = get_handle(ino)) != OK)
return r;
pos = *posp;
count = *countp;
assert(count > 0);
/* Use the buffer from below to eliminate extra copying. */
size = sffs_table->t_writebuf(&ptr);
off = 0;
while (count > 0) {
chunk = MIN(count, size);
if (grantp != NULL) {
r = sys_safecopyfrom(m_in.m_source, *grantp,
off, (vir_bytes) ptr, chunk);
if (r != OK)
break;
} else {
/* Do this every time. We don't know what happens below. */
memset(ptr, 0, chunk);
}
if ((r = sffs_table->t_write(ino->i_file, ptr, chunk, pos)) <= 0)
break;
count -= r;
off += r;
pos += r;
}
if (r < 0)
return r;
*posp = pos;
*countp = off;
return OK;
}
/*===========================================================================*
* do_write *
*===========================================================================*/
int do_write(void)
{
/* Write data to a file.
*/
struct inode *ino;
off_t pos;
size_t count;
cp_grant_id_t grant;
int r;
if (state.s_read_only)
return EROFS;
if ((ino = find_inode(m_in.m_vfs_fs_readwrite.inode)) == NULL)
return EINVAL;
if (IS_DIR(ino)) return EISDIR;
pos = m_in.m_vfs_fs_readwrite.seek_pos;
count = m_in.m_vfs_fs_readwrite.nbytes;
grant = m_in.m_vfs_fs_readwrite.grant;
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if (count == 0) return EINVAL;
if ((r = write_file(ino, &pos, &count, &grant)) != OK)
return r;
m_out.m_fs_vfs_readwrite.seek_pos = pos;
m_out.m_fs_vfs_readwrite.nbytes = count;
return OK;
}
/*===========================================================================*
* do_ftrunc *
*===========================================================================*/
int do_ftrunc(void)
{
/* Change file size or create file holes.
*/
char path[PATH_MAX];
struct inode *ino;
struct sffs_attr attr;
u64_t start, end, delta;
size_t count;
int r;
if (state.s_read_only)
return EROFS;
if ((ino = find_inode(m_in.m_vfs_fs_ftrunc.inode)) == NULL)
return EINVAL;
if (IS_DIR(ino)) return EISDIR;
start = m_in.m_vfs_fs_ftrunc.trc_start;
end = m_in.m_vfs_fs_ftrunc.trc_end;
if (end == 0) {
/* Truncate or expand the file. */
if ((r = verify_inode(ino, path, NULL)) != OK)
return r;
attr.a_mask = SFFS_ATTR_SIZE;
attr.a_size = start;
r = sffs_table->t_setattr(path, &attr);
} else {
/* Write zeroes to the file. We can't create holes. */
if (end <= start) return EINVAL;
delta = end - start;
if (ex64hi(delta) != 0) return EINVAL;
count = ex64lo(delta);
r = write_file(ino, &start, &count, NULL);
}
return r;
}