bd3cde4571
Add primary cache management feature to libminixfs as mfs and ext2
currently do separately, remove cache code from mfs and ext2, and make
them use the libminixfs interface. This makes all fields of the buf
struct private to libminixfs and FS clients aren't supposed to access
them at all. Only the opaque 'void *data' field (the FS block contents,
used to be called bp) is to be accessed by the FS client.
The main purpose is to implement the interface to the 2ndary vm cache
just once, get rid of some code duplication, and add a little
abstraction to reduce the code inertia of the whole caching business.
Some minor sanity checking and prohibition done by mfs in this code
as removed from the generic primary cache code as a result:
- checking all inodes are not in use when allocating/resizing
the cache
- checking readonly filesystems aren't written to
- checking the superblock isn't written to on mounted filesystems
The minixfslib code relies on fs_blockstats() in the client filesystem to
return some FS usage information.
159 lines
4.3 KiB
C
159 lines
4.3 KiB
C
/* Created (MFS based):
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* February 2010 (Evgeniy Ivanov)
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*/
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#include "fs.h"
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#include "inode.h"
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#include "super.h"
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#include <minix/vfsif.h>
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static int in_group(gid_t grp);
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/*===========================================================================*
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* fs_chmod *
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*===========================================================================*/
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int fs_chmod()
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{
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/* Perform the chmod(name, mode) system call. */
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register struct inode *rip;
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mode_t mode;
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mode = (mode_t) fs_m_in.REQ_MODE;
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/* Temporarily open the file. */
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if( (rip = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
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return(EINVAL);
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/* Now make the change. Clear setgid bit if file is not in caller's grp */
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rip->i_mode = (rip->i_mode & ~ALL_MODES) | (mode & ALL_MODES);
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rip->i_update |= CTIME;
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rip->i_dirt = IN_DIRTY;
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/* Return full new mode to caller. */
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fs_m_out.RES_MODE = rip->i_mode;
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put_inode(rip);
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return(OK);
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}
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/*===========================================================================*
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* fs_chown *
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*===========================================================================*/
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int fs_chown()
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{
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register struct inode *rip;
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register int r;
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/* Temporarily open the file. */
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if( (rip = get_inode(fs_dev, (ino_t) fs_m_in.REQ_INODE_NR)) == NULL)
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return(EINVAL);
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/* Not permitted to change the owner of a file on a read-only file sys. */
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r = read_only(rip);
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if (r == OK) {
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rip->i_uid = fs_m_in.REQ_UID;
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rip->i_gid = fs_m_in.REQ_GID;
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rip->i_mode &= ~(I_SET_UID_BIT | I_SET_GID_BIT);
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rip->i_update |= CTIME;
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rip->i_dirt = IN_DIRTY;
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}
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/* Update caller on current mode, as it may have changed. */
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fs_m_out.RES_MODE = rip->i_mode;
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put_inode(rip);
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return(r);
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}
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/*===========================================================================*
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* forbidden *
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*===========================================================================*/
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int forbidden(register struct inode *rip, mode_t access_desired)
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{
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/* Given a pointer to an inode, 'rip', and the access desired, determine
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* if the access is allowed, and if not why not. The routine looks up the
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* caller's uid in the 'fproc' table. If access is allowed, OK is returned
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* if it is forbidden, EACCES is returned.
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*/
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register struct inode *old_rip = rip;
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register mode_t bits, perm_bits;
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int r, shift;
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/* Isolate the relevant rwx bits from the mode. */
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bits = rip->i_mode;
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if (caller_uid == SU_UID) {
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/* Grant read and write permission. Grant search permission for
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* directories. Grant execute permission (for non-directories) if
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* and only if one of the 'X' bits is set.
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*/
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if ( (bits & I_TYPE) == I_DIRECTORY ||
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bits & ((X_BIT << 6) | (X_BIT << 3) | X_BIT))
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perm_bits = R_BIT | W_BIT | X_BIT;
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else
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perm_bits = R_BIT | W_BIT;
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} else {
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if (caller_uid == rip->i_uid) shift = 6; /* owner */
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else if (caller_gid == rip->i_gid) shift = 3; /* group */
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else if (in_group(rip->i_gid) == OK) shift = 3; /* other groups */
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else shift = 0; /* other */
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perm_bits = (bits >> shift) & (R_BIT | W_BIT | X_BIT);
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}
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/* If access desired is not a subset of what is allowed, it is refused. */
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r = OK;
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if ((perm_bits | access_desired) != perm_bits) r = EACCES;
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/* Check to see if someone is trying to write on a file system that is
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* mounted read-only.
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*/
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if (r == OK) {
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if (access_desired & W_BIT) {
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r = read_only(rip);
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}
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}
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if (rip != old_rip) put_inode(rip);
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return(r);
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}
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/*===========================================================================*
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* in_group *
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*===========================================================================*/
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static int in_group(gid_t grp)
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{
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int i;
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if (credentials.vu_ngroups > NGROUPS_MAX)
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return(EINVAL);
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for (i = 0; i < credentials.vu_ngroups; i++)
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if (credentials.vu_sgroups[i] == grp)
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return(OK);
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return(EINVAL);
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}
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/*===========================================================================*
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* read_only *
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*===========================================================================*/
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int read_only(ip)
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struct inode *ip; /* ptr to inode whose file sys is to be cked */
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{
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/* Check to see if the file system on which the inode 'ip' resides is mounted
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* read only. If so, return EROFS, else return OK.
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*/
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register struct super_block *sp;
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sp = ip->i_sp;
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return(sp->s_rd_only ? EROFS : OK);
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}
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