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SubjectRe: 2.4.20pre5aa1
On Thu, Sep 05, 2002 at 07:46:49PM +0100, Christoph Hellwig wrote:
> On Thu, Sep 05, 2002 at 08:41:25PM +0200, Andrea Arcangeli wrote:
> > maybe I'm overlooking something but after a short read it seems you have
> > no lock in do_truncate->setattr like for all the other fs, so the
> > vmtruncate can run under reads and the i_size can change under you and
> > in turn you must always read it with i_size_read using asm, like all the
> > other fs, if you're not holding the i_sem (and you certainly aren't
> > holding the i_sem that frequently, you don't even for writes). this
> > because i_sem is the only lock/sem hold by truncate. Infact I'm unsure
> > how you serialize the i_size writes of truncate against the ones from
> > writes, that seems problematic too, the i_size could get a value past
> > the last block allocated (in turn corrupting the fs). Please double
> > check that I'm wrong, thanks.
>
> I think we should take the XFS-specific inode lock around vmtruncate.
> Need to double-check with Steve.

this is the function I'm looking at and it's called with xfs specific
inode lock, and I don't see it grabbed either before calling vmtruncate:

+STATIC int
+linvfs_setattr(
+ struct dentry *dentry,
+ struct iattr *attr)
+{
+ struct inode *inode = dentry->d_inode;
+ vnode_t *vp = LINVFS_GET_VP(inode);
+ vattr_t vattr;
+ unsigned int ia_valid = attr->ia_valid;
+ int error;
+ int flags = 0;
+
+ memset(&vattr, 0, sizeof(vattr_t));
+ if (ia_valid & ATTR_UID) {
+ vattr.va_mask |= AT_UID;
+ vattr.va_uid = attr->ia_uid;
+ }
+ if (ia_valid & ATTR_GID) {
+ vattr.va_mask |= AT_GID;
+ vattr.va_gid = attr->ia_gid;
+ }
+ if (ia_valid & ATTR_SIZE) {
+ vattr.va_mask |= AT_SIZE;
+ vattr.va_size = attr->ia_size;
+ }
+ if (ia_valid & ATTR_ATIME) {
+ vattr.va_mask |= AT_ATIME;
+ vattr.va_atime.tv_sec = attr->ia_atime;
+ vattr.va_atime.tv_nsec = 0;
+ }
+ if (ia_valid & ATTR_MTIME) {
+ vattr.va_mask |= AT_MTIME;
+ vattr.va_mtime.tv_sec = attr->ia_mtime;
+ vattr.va_mtime.tv_nsec = 0;
+ }
+ if (ia_valid & ATTR_CTIME) {
+ vattr.va_mask |= AT_CTIME;
+ vattr.va_ctime.tv_sec = attr->ia_ctime;
+ vattr.va_ctime.tv_nsec = 0;
+ }
+ if (ia_valid & ATTR_MODE) {
+ vattr.va_mask |= AT_MODE;
+ vattr.va_mode = attr->ia_mode;
+ if (!in_group_p(inode->i_gid) && !capable(CAP_FSETID))
+ inode->i_mode &= ~S_ISGID;
+ }
+
+ if (ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET))
+ flags = ATTR_UTIME;
+
+ VOP_SETATTR(vp, &vattr, flags, NULL, error);
+ if (error)
+ return(-error); /* Positive error up from XFS */
+ if (ia_valid & ATTR_SIZE) {
+ error = vmtruncate(inode, attr->ia_size);
+ }
+
+ if (!error) {
+ vn_revalidate(vp, 0);
+ mark_inode_dirty_sync(inode);
+ }
+ return error;
+}

Andrea
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