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Rick Macklem authored
Without this patch, if a pNFS read layout has already been acquired for a file, writes would be redirected to the Metadata Server (MDS), because nfscl_getlayout() would not acquire a read/write layout for the file. This happened because there was no "mode" argument to nfscl_getlayout() to indicate whether reading or writing was being done. Since doing I/O through the Metadata Server is not encouraged for some pNFS servers, it is preferable to get a read/write layout for writes instead of redirecting the write to the MDS. This patch adds a access mode argument to nfscl_getlayout() and nfsrpc_getlayout(), so that nfscl_getlayout() knows to acquire a read/write layout for writing, even if a read layout has already been acquired. This patch only affects NFSv4.1/4.2 client behaviour when pNFS ("pnfs" mount option against a server that supports pNFS) is in use. This problem was detected during a recent NFSv4 interoperability testing event held by the IETF working group. MFC after: 2 week
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