- introduce new call numbers, names, and field aliases; - initialize request messages to zero for all ABI calls; - format callnr.h in the same way as com.h; - redo call tables in both servers; - remove param.h namespace pollution in the servers; - make brk(2) go to VM directly, rather than through PM; - remove obsolete BRK, UTIME, and WAIT calls; - clean up path copying routine in VFS; - move remaining system calls from libminlib to libc; - correct some errno-related mistakes in libc routines. Change-Id: I2d8ec5d061cd7e0b30c51ffd77aa72ebf84e2565
185 lines
5.7 KiB
C
185 lines
5.7 KiB
C
/* This file handles advisory file locking as required by POSIX.
|
|
*
|
|
* The entry points into this file are
|
|
* lock_op: perform locking operations for FCNTL system call
|
|
* lock_revive: revive processes when a lock is released
|
|
*/
|
|
|
|
#include "fs.h"
|
|
#include <minix/com.h>
|
|
#include <minix/u64.h>
|
|
#include <fcntl.h>
|
|
#include <unistd.h>
|
|
#include "file.h"
|
|
#include "scratchpad.h"
|
|
#include "lock.h"
|
|
#include "vnode.h"
|
|
|
|
/*===========================================================================*
|
|
* lock_op *
|
|
*===========================================================================*/
|
|
int lock_op(f, req)
|
|
struct filp *f;
|
|
int req; /* either F_SETLK or F_SETLKW */
|
|
{
|
|
/* Perform the advisory locking required by POSIX. */
|
|
|
|
int r, ltype, i, conflict = 0, unlocking = 0;
|
|
mode_t mo;
|
|
off_t first, last;
|
|
struct flock flock;
|
|
struct file_lock *flp, *flp2, *empty;
|
|
|
|
/* Fetch the flock structure from user space. */
|
|
r = sys_datacopy(who_e, (vir_bytes) scratch(fp).io.io_buffer, VFS_PROC_NR,
|
|
(vir_bytes) &flock, sizeof(flock));
|
|
if (r != OK) return(EINVAL);
|
|
|
|
/* Make some error checks. */
|
|
ltype = flock.l_type;
|
|
mo = f->filp_mode;
|
|
if (ltype != F_UNLCK && ltype != F_RDLCK && ltype != F_WRLCK) return(EINVAL);
|
|
if (req == F_GETLK && ltype == F_UNLCK) return(EINVAL);
|
|
if (!S_ISREG(f->filp_vno->v_mode) && !S_ISBLK(f->filp_vno->v_mode))
|
|
return(EINVAL);
|
|
if (req != F_GETLK && ltype == F_RDLCK && (mo & R_BIT) == 0) return(EBADF);
|
|
if (req != F_GETLK && ltype == F_WRLCK && (mo & W_BIT) == 0) return(EBADF);
|
|
|
|
/* Compute the first and last bytes in the lock region. */
|
|
switch (flock.l_whence) {
|
|
case SEEK_SET: first = 0; break;
|
|
case SEEK_CUR: first = f->filp_pos; break;
|
|
case SEEK_END: first = f->filp_vno->v_size; break;
|
|
default: return(EINVAL);
|
|
}
|
|
|
|
/* Check for overflow. */
|
|
if (((long) flock.l_start > 0) && ((first + flock.l_start) < first))
|
|
return(EINVAL);
|
|
if (((long) flock.l_start < 0) && ((first + flock.l_start) > first))
|
|
return(EINVAL);
|
|
first = first + flock.l_start;
|
|
last = first + flock.l_len - 1;
|
|
if (flock.l_len == 0) last = MAX_FILE_POS;
|
|
if (last < first) return(EINVAL);
|
|
|
|
/* Check if this region conflicts with any existing lock. */
|
|
empty = NULL;
|
|
for (flp = &file_lock[0]; flp < &file_lock[NR_LOCKS]; flp++) {
|
|
if (flp->lock_type == 0) {
|
|
if (empty == NULL) empty = flp;
|
|
continue; /* 0 means unused slot */
|
|
}
|
|
if (flp->lock_vnode != f->filp_vno) continue; /* different file */
|
|
if (last < flp->lock_first) continue; /* new one is in front */
|
|
if (first > flp->lock_last) continue; /* new one is afterwards */
|
|
if (ltype == F_RDLCK && flp->lock_type == F_RDLCK) continue;
|
|
if (ltype != F_UNLCK && flp->lock_pid == fp->fp_pid) continue;
|
|
|
|
/* There might be a conflict. Process it. */
|
|
conflict = 1;
|
|
if (req == F_GETLK) break;
|
|
|
|
/* If we are trying to set a lock, it just failed. */
|
|
if (ltype == F_RDLCK || ltype == F_WRLCK) {
|
|
if (req == F_SETLK) {
|
|
/* For F_SETLK, just report back failure. */
|
|
return(EAGAIN);
|
|
} else {
|
|
/* For F_SETLKW, suspend the process. */
|
|
suspend(FP_BLOCKED_ON_LOCK);
|
|
return(SUSPEND);
|
|
}
|
|
}
|
|
|
|
/* We are clearing a lock and we found something that overlaps. */
|
|
unlocking = 1;
|
|
if (first <= flp->lock_first && last >= flp->lock_last) {
|
|
flp->lock_type = 0; /* mark slot as unused */
|
|
nr_locks--; /* number of locks is now 1 less */
|
|
continue;
|
|
}
|
|
|
|
/* Part of a locked region has been unlocked. */
|
|
if (first <= flp->lock_first) {
|
|
flp->lock_first = last + 1;
|
|
continue;
|
|
}
|
|
|
|
if (last >= flp->lock_last) {
|
|
flp->lock_last = first - 1;
|
|
continue;
|
|
}
|
|
|
|
/* Bad luck. A lock has been split in two by unlocking the middle. */
|
|
if (nr_locks == NR_LOCKS) return(ENOLCK);
|
|
for (i = 0; i < NR_LOCKS; i++)
|
|
if (file_lock[i].lock_type == 0) break;
|
|
flp2 = &file_lock[i];
|
|
flp2->lock_type = flp->lock_type;
|
|
flp2->lock_pid = flp->lock_pid;
|
|
flp2->lock_vnode = flp->lock_vnode;
|
|
flp2->lock_first = last + 1;
|
|
flp2->lock_last = flp->lock_last;
|
|
flp->lock_last = first - 1;
|
|
nr_locks++;
|
|
}
|
|
if (unlocking) lock_revive();
|
|
|
|
if (req == F_GETLK) {
|
|
if (conflict) {
|
|
/* GETLK and conflict. Report on the conflicting lock. */
|
|
flock.l_type = flp->lock_type;
|
|
flock.l_whence = SEEK_SET;
|
|
flock.l_start = flp->lock_first;
|
|
flock.l_len = flp->lock_last - flp->lock_first + 1;
|
|
flock.l_pid = flp->lock_pid;
|
|
|
|
} else {
|
|
/* It is GETLK and there is no conflict. */
|
|
flock.l_type = F_UNLCK;
|
|
}
|
|
|
|
/* Copy the flock structure back to the caller. */
|
|
r = sys_datacopy(VFS_PROC_NR, (vir_bytes) &flock, who_e,
|
|
(vir_bytes) scratch(fp).io.io_buffer, sizeof(flock));
|
|
return(r);
|
|
}
|
|
|
|
if (ltype == F_UNLCK) return(OK); /* unlocked a region with no locks */
|
|
|
|
/* There is no conflict. If space exists, store new lock in the table. */
|
|
if (empty == NULL) return(ENOLCK); /* table full */
|
|
empty->lock_type = ltype;
|
|
empty->lock_pid = fp->fp_pid;
|
|
empty->lock_vnode = f->filp_vno;
|
|
empty->lock_first = first;
|
|
empty->lock_last = last;
|
|
nr_locks++;
|
|
return(OK);
|
|
}
|
|
|
|
|
|
/*===========================================================================*
|
|
* lock_revive *
|
|
*===========================================================================*/
|
|
void lock_revive()
|
|
{
|
|
/* Go find all the processes that are waiting for any kind of lock and
|
|
* revive them all. The ones that are still blocked will block again when
|
|
* they run. The others will complete. This strategy is a space-time
|
|
* tradeoff. Figuring out exactly which ones to unblock now would take
|
|
* extra code, and the only thing it would win would be some performance in
|
|
* extremely rare circumstances (namely, that somebody actually used
|
|
* locking).
|
|
*/
|
|
|
|
struct fproc *fptr;
|
|
|
|
for (fptr = &fproc[0]; fptr < &fproc[NR_PROCS]; fptr++){
|
|
if (fptr->fp_pid == PID_FREE) continue;
|
|
if (fptr->fp_blocked_on == FP_BLOCKED_ON_LOCK) {
|
|
revive(fptr->fp_endpoint, 0);
|
|
}
|
|
}
|
|
}
|