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Fix the pNFS flexible file layout client for servers with small write size.

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The code in nfscl_dofflayout() loops when a flexible file layout server
provides a small write data limit (no extant server is known to do this).
If/when it looped, it erroneously reused the "drpc" argument for the
mirror worker thread, corrupting it.
This patch fixes the problem by only using the calling thread after the
first loop iteration.

Found during testing by simulating a server with a small write size.

Since no extant pNFS server is known to provide a small write size,
this fix it not needed in practice at this time.

MFC after:	2 weeks
This commit is contained in:
Rick Macklem 2020-07-15 01:26:28 +00:00
parent 984c1095a4
commit 7477442fdd
1 changed files with 9 additions and 2 deletions
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11
sys/fs/nfsclient/nfs_clrpcops.c
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@ -6248,10 +6248,17 @@ nfscl_dofflayoutio(vnode_t vp, struct uio *uiop, int *iomode, int *must_commit,
NFSCL_DEBUG(4, "mcopy reloff=%d xfer=%jd\n",
rel_off, (uintmax_t)xfer);
/*
* Do last write to a mirrored DS with this
* Do the writes after the first loop iteration
* and the write for the last mirror via this
* thread.
* This loop only iterates for small values
* of nfsdi_wsize, which may never occur in
* practice. However, the drpc is completely
* used by the first iteration and, as such,
* cannot be used after that.
*/
if (mirror < flp->nfsfl_mirrorcnt - 1)
if (mirror < flp->nfsfl_mirrorcnt - 1 &&
rel_off == 0)
error = nfsio_writedsmir(vp, iomode,
must_commit, stateidp, *dspp, off,
xfer, fhp, m, dp->nfsdi_vers,