minix3/lib/libsffs/link.c

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2020-02-21 00:59:27 +05:30
/* This file contains directory entry related file system call handlers.
*
* The entry points into this file are:
* do_create perform the CREATE file system call
* do_mkdir perform the MKDIR file system call
* do_unlink perform the UNLINK file system call
* do_rmdir perform the RMDIR file system call
* do_rename perform the RENAME file system call
*
* Created:
* April 2009 (D.C. van Moolenbroek)
*/
#include "inc.h"
#include <fcntl.h>
static int force_remove(char *path, int dir);
/*===========================================================================*
* do_create *
*===========================================================================*/
int do_create(void)
{
/* Create a new file.
*/
char path[PATH_MAX], name[NAME_MAX+1];
struct inode *parent, *ino;
struct sffs_attr attr;
sffs_file_t handle;
int r;
/* We cannot create files on a read-only file system. */
if (state.s_read_only)
return EROFS;
/* Get path, name, parent inode and possibly inode for the given path. */
if ((r = get_name(m_in.m_vfs_fs_create.grant, m_in.m_vfs_fs_create.path_len, name)) != OK)
return r;
if (!strcmp(name, ".") || !strcmp(name, "..")) return EEXIST;
if ((parent = find_inode(m_in.m_vfs_fs_create.inode)) == NULL)
return EINVAL;
if ((r = verify_dentry(parent, name, path, &ino)) != OK)
return r;
/* Are we going to need a new inode upon success?
* Then make sure there is one available before trying anything.
*/
if (ino == NULL || ino->i_ref > 1 || HAS_CHILDREN(ino)) {
if (!have_free_inode()) {
if (ino != NULL)
put_inode(ino);
return ENFILE;
}
}
/* Perform the actual create call. */
r = sffs_table->t_open(path, O_CREAT | O_EXCL | O_RDWR, m_in.m_vfs_fs_create.mode,
&handle);
if (r != OK) {
/* Let's not try to be too clever with error codes here. If something
* is wrong with the directory, we'll find out later anyway.
*/
if (ino != NULL)
put_inode(ino);
return r;
}
/* Get the created file's attributes. */
attr.a_mask = SFFS_ATTR_MODE | SFFS_ATTR_SIZE;
r = sffs_table->t_getattr(path, &attr);
/* If this fails, or returns a directory, we have a problem. This
* scenario is in fact possible with race conditions.
* Simulate a close and return a somewhat appropriate error.
*/
if (r != OK || S_ISDIR(attr.a_mode)) {
printf("%s: lost file after creation!\n", sffs_name);
sffs_table->t_close(handle);
if (ino != NULL) {
del_dentry(ino);
put_inode(ino);
}
return (r == OK) ? EEXIST : r;
}
/* We do assume that the underlying open(O_CREAT|O_EXCL) call did its job.
* If we previousy found an inode, get rid of it now. It's old.
*/
if (ino != NULL) {
del_dentry(ino);
put_inode(ino);
}
/* Associate the open file handle with an inode, and reply with its details.
*/
ino = get_free_inode();
assert(ino != NULL); /* we checked before whether we had a free one */
ino->i_file = handle;
ino->i_flags = I_HANDLE;
add_dentry(parent, name, ino);
m_out.m_fs_vfs_create.inode = INODE_NR(ino);
m_out.m_fs_vfs_create.mode = get_mode(ino, attr.a_mode);
m_out.m_fs_vfs_create.file_size = attr.a_size;
m_out.m_fs_vfs_create.uid = sffs_params->p_uid;
m_out.m_fs_vfs_create.gid = sffs_params->p_gid;
return OK;
}
/*===========================================================================*
* do_mkdir *
*===========================================================================*/
int do_mkdir(void)
{
/* Make a new directory.
*/
char path[PATH_MAX], name[NAME_MAX+1];
struct inode *parent, *ino;
int r;
/* We cannot create directories on a read-only file system. */
if (state.s_read_only)
return EROFS;
/* Get the path string and possibly an inode for the given path. */
if ((r = get_name(m_in.m_vfs_fs_mkdir.grant, m_in.m_vfs_fs_mkdir.path_len, name)) != OK)
return r;
if (!strcmp(name, ".") || !strcmp(name, "..")) return EEXIST;
if ((parent = find_inode(m_in.m_vfs_fs_mkdir.inode)) == NULL)
return EINVAL;
if ((r = verify_dentry(parent, name, path, &ino)) != OK)
return r;
/* Perform the actual mkdir call. */
r = sffs_table->t_mkdir(path, m_in.m_vfs_fs_mkdir.mode);
if (r != OK) {
if (ino != NULL)
put_inode(ino);
return r;
}
/* If we thought the new dentry already existed, it was apparently gone
* already. Delete it.
*/
if (ino != NULL) {
del_dentry(ino);
put_inode(ino);
}
return OK;
}
/*===========================================================================*
* force_remove *
*===========================================================================*/
static int force_remove(
char *path, /* path to file or directory */
int dir /* TRUE iff directory */
)
{
/* Remove a file or directory. Wrapper around unlink and rmdir that makes the
* target temporarily writable if the operation fails with an access denied
* error. On Windows hosts, read-only files or directories cannot be removed
* (even though they can be renamed). In general, the SFFS library follows the
* behavior of the host file system, but this case just confuses the hell out
* of the MINIX userland..
*/
struct sffs_attr attr;
int r, r2;
/* First try to remove the target. */
if (dir)
r = sffs_table->t_rmdir(path);
else
r = sffs_table->t_unlink(path);
if (r != EACCES) return r;
/* If this fails with an access error, retrieve the target's mode. */
attr.a_mask = SFFS_ATTR_MODE;
r2 = sffs_table->t_getattr(path, &attr);
if (r2 != OK || (attr.a_mode & S_IWUSR)) return r;
/* If the target is not writable, temporarily set it to writable. */
attr.a_mode |= S_IWUSR;
r2 = sffs_table->t_setattr(path, &attr);
if (r2 != OK) return r;
/* Then try the original operation again. */
if (dir)
r = sffs_table->t_rmdir(path);
else
r = sffs_table->t_unlink(path);
if (r == OK) return r;
/* If the operation still fails, unset the writable bit again. */
attr.a_mode &= ~S_IWUSR;
sffs_table->t_setattr(path, &attr);
return r;
}
/*===========================================================================*
* do_unlink *
*===========================================================================*/
int do_unlink(void)
{
/* Delete a file.
*/
char path[PATH_MAX], name[NAME_MAX+1];
struct inode *parent, *ino;
int r;
/* We cannot delete files on a read-only file system. */
if (state.s_read_only)
return EROFS;
/* Get the path string and possibly preexisting inode for the given path. */
if ((r = get_name(m_in.m_vfs_fs_unlink.grant, m_in.m_vfs_fs_unlink.path_len, name)) != OK)
return r;
if (!strcmp(name, ".") || !strcmp(name, "..")) return EPERM;
if ((parent = find_inode(m_in.m_vfs_fs_unlink.inode)) == NULL)
return EINVAL;
if ((r = verify_dentry(parent, name, path, &ino)) != OK)
return r;
/* Perform the unlink call. */
r = force_remove(path, FALSE /*dir*/);
if (r != OK) {
if (ino != NULL)
put_inode(ino);
return r;
}
/* If a dentry existed for this name, it is gone now. */
if (ino != NULL) {
del_dentry(ino);
put_inode(ino);
}
return OK;
}
/*===========================================================================*
* do_rmdir *
*===========================================================================*/
int do_rmdir(void)
{
/* Remove an empty directory.
*/
char path[PATH_MAX], name[NAME_MAX+1];
struct inode *parent, *ino;
int r;
/* We cannot remove directories on a read-only file system. */
if (state.s_read_only)
return EROFS;
/* Get the path string and possibly preexisting inode for the given path. */
if ((r = get_name(m_in.m_vfs_fs_unlink.grant, m_in.m_vfs_fs_unlink.path_len, name)) != OK)
return r;
if (!strcmp(name, ".")) return EINVAL;
if (!strcmp(name, "..")) return ENOTEMPTY;
if ((parent = find_inode(m_in.m_vfs_fs_unlink.inode)) == NULL)
return EINVAL;
if ((r = verify_dentry(parent, name, path, &ino)) != OK)
return r;
/* Perform the rmdir call. */
r = force_remove(path, TRUE /*dir*/);
if (r != OK) {
if (ino != NULL)
put_inode(ino);
return r;
}
/* If a dentry existed for this name, it is gone now. */
if (ino != NULL) {
del_dentry(ino);
put_inode(ino);
}
return OK;
}
/*===========================================================================*
* do_rename *
*===========================================================================*/
int do_rename(void)
{
/* Rename a file or directory.
*/
char old_path[PATH_MAX], new_path[PATH_MAX];
char old_name[NAME_MAX+1], new_name[NAME_MAX+1];
struct inode *old_parent, *new_parent;
struct inode *old_ino, *new_ino;
int r;
/* We cannot do rename on a read-only file system. */
if (state.s_read_only)
return EROFS;
/* Get path strings, names, directory inodes and possibly preexisting inodes
* for the old and new paths.
*/
if ((r = get_name(m_in.m_vfs_fs_rename.grant_old, m_in.m_vfs_fs_rename.len_old,
old_name)) != OK) return r;
if ((r = get_name(m_in.m_vfs_fs_rename.grant_new, m_in.m_vfs_fs_rename.len_new,
new_name)) != OK) return r;
if (!strcmp(old_name, ".") || !strcmp(old_name, "..") ||
!strcmp(new_name, ".") || !strcmp(new_name, "..")) return EINVAL;
if ((old_parent = find_inode(m_in.m_vfs_fs_rename.dir_old)) == NULL ||
(new_parent = find_inode(m_in.m_vfs_fs_rename.dir_new)) == NULL)
return EINVAL;
if ((r = verify_dentry(old_parent, old_name, old_path, &old_ino)) != OK)
return r;
if ((r = verify_dentry(new_parent, new_name, new_path, &new_ino)) != OK) {
if (old_ino != NULL)
put_inode(old_ino);
return r;
}
/* Perform the actual rename call. */
r = sffs_table->t_rename(old_path, new_path);
/* If we failed, or if we have nothing further to do: both inodes are
* NULL, or they both refer to the same file.
*/
if (r != OK || old_ino == new_ino) {
if (old_ino != NULL) put_inode(old_ino);
if (new_ino != NULL) put_inode(new_ino);
return r;
}
/* If the new dentry already existed, it has now been overwritten.
* Delete the associated inode if we had found one.
*/
if (new_ino != NULL) {
del_dentry(new_ino);
put_inode(new_ino);
}
/* If the old dentry existed, rename it accordingly. */
if (old_ino != NULL) {
del_dentry(old_ino);
add_dentry(new_parent, new_name, old_ino);
put_inode(old_ino);
}
return OK;
}