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XXX Copy workaround from UFS: open device for write access even if

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the user requests a read-only mount. This is necessary because we
don't do the VOP_OPEN again if they upgrade a read-only mount to
read-write.

Fixes lockup when creating files on msdosfs mounts that have been
mounted read-only then upgraded to read-write. The exact cause of
the lockup is not known, but it is likely to be the kernel getting
stuck in an infinite loop trying to write dirty buffers to a device
without write permission.

Reported/tested by andreas, discussed with phk.
This commit is contained in:
Tim J. Robbins 2003-06-29 03:05:59 +00:00
parent fd05df3205
commit ae620d4480
1 changed files with 19 additions and 0 deletions
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19
sys/fs/msdosfs/msdosfs_vfsops.c
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@ -318,7 +318,16 @@ mountmsdosfs(devvp, mp, td, argp)
ronly = (mp->mnt_flag & MNT_RDONLY) != 0;
vn_lock(devvp, LK_EXCLUSIVE | LK_RETRY, td);
/*
* XXX Open the device with write access even if the filesystem
* is read-only: someone may remount it read-write later, and
* we don't VOP_OPEN the device again in that case.
*/
#ifdef notyet
error = VOP_OPEN(devvp, ronly ? FREAD : FREAD|FWRITE, FSCRED, td);
#else
error = VOP_OPEN(devvp, FREAD|FWRITE, FSCRED, td);
#endif
VOP_UNLOCK(devvp, 0, td);
if (error)
return (error);
@ -607,7 +616,12 @@ mountmsdosfs(devvp, mp, td, argp)
error_exit:
if (bp)
brelse(bp);
/* XXX See comment at VOP_OPEN call */
#ifdef notyet
(void) VOP_CLOSE(devvp, ronly ? FREAD : FREAD | FWRITE, NOCRED, td);
#else
(void) VOP_CLOSE(devvp, FREAD | FWRITE, NOCRED, td);
#endif
if (pmp) {
if (pmp->pm_inusemap)
free(pmp->pm_inusemap, M_MSDOSFSFAT);
@ -662,9 +676,14 @@ msdosfs_unmount(mp, mntflags, td)
VI_UNLOCK(vp);
}
#endif
/* XXX See comment at VOP_OPEN call */
#ifdef notyet
error = VOP_CLOSE(pmp->pm_devvp,
(pmp->pm_flags&MSDOSFSMNT_RONLY) ? FREAD : FREAD | FWRITE,
NOCRED, td);
#else
error = VOP_CLOSE(pmp->pm_devvp, FREAD | FWRITE, NOCRED, td);
#endif
vrele(pmp->pm_devvp);
free(pmp->pm_inusemap, M_MSDOSFSFAT);
free(pmp, M_MSDOSFSMNT);