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A problem with the old NFS client where large writes to large files

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would sometimes result in a corrupted file was reported via email.
This problem appears to have been caused by r251719 (reverting
r251719 fixed the problem). Although I have not been able to
reproduce this problem, I suspect it is caused by another thread
increasing np->n_size after the mtx_unlock(&np->n_mtx) but before
the vnode_pager_setsize() call. Since the np->n_mtx mutex serializes
updates to np->n_size, doing the vnode_pager_setsize() with the
mutex locked appears to avoid the problem.
Unfortunately, vnode_pager_setsize() where the new size is smaller,
cannot be called with a mutex held.
This patch returns the semantics to be close to pre-r251719 such that the
call to the vnode_pager_setsize() is only delayed until after the mutex is
unlocked when np->n_size is shrinking. Since the file is growing
when being written, I believe this will fix the corruption.

Reported by:	David G. Lawrence (dg@dglawrence.com)
Tested by:	David G. Lawrence (pending, to happen soon)
Reviewed by:	kib
MFC after:	1 week
This commit is contained in:
rmacklem 2013-07-04 00:54:23 +00:00
parent 4a1b5780c0
commit 13e7ae9b12
1 changed files with 13 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
sys/nfsclient/nfs_subs.c
View File

@ -581,6 +581,7 @@ nfs_loadattrcache(struct vnode **vpp, struct mbuf **mdp, caddr_t *dposp,
vap->va_size = np->n_size;
np->n_attrstamp = 0;
KDTRACE_NFS_ATTRCACHE_FLUSH_DONE(vp);
vnode_pager_setsize(vp, np->n_size);
} else if (np->n_flag & NMODIFIED) {
/*
* We've modified the file: Use the larger
@ -592,12 +593,22 @@ nfs_loadattrcache(struct vnode **vpp, struct mbuf **mdp, caddr_t *dposp,
np->n_size = vap->va_size;
np->n_flag |= NSIZECHANGED;
}
vnode_pager_setsize(vp, np->n_size);
} else if (vap->va_size < np->n_size) {
/*
* When shrinking the size, the call to
* vnode_pager_setsize() cannot be done
* with the mutex held, so delay it until
* after the mtx_unlock call.
*/
nsize = np->n_size = vap->va_size;
np->n_flag |= NSIZECHANGED;
setnsize = 1;
} else {
np->n_size = vap->va_size;
np->n_flag |= NSIZECHANGED;
vnode_pager_setsize(vp, np->n_size);
}
setnsize = 1;
nsize = vap->va_size;
} else {
np->n_size = vap->va_size;
}