nfsd: only call inode_query_iversion in the I_VERSION case

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inode_query_iversion() can modify i_version.  Depending on the exported
filesystem, that may not be safe.  For example, if you're re-exporting
NFS, NFS stores the server's change attribute in i_version and does not
expect it to be modified locally.  This has been observed causing
unnecessary cache invalidations.

The way a filesystem indicates that it's OK to call
inode_query_iverson() is by setting SB_I_VERSION.

So, move the I_VERSION check out of encode_change(), where it's used
only in GETATTR responses, to nfsd4_change_attribute(), which is
also called for pre- and post- operation attributes.

(Note we could also pull the NFSEXP_V4ROOT case into
nfsd4_change_attribute() as well.  That would actually be a no-op,
since pre/post attrs are only used for metadata-modifying operations,
and V4ROOT exports are read-only.  But we might make the change in
the future just for simplicity.)

Reported-by: Daire Byrne <daire@dneg.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

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This commit is contained in:

J. Bruce Fields 2020-11-30 17:46:14 -05:00 • committed by Chuck Lever

parent 4a9d81caf8

commit 70b87f7729

3 changed files with 13 additions and 12 deletions

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5

fs/nfsd/nfs3xdr.c

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fs/nfsd/nfs4xdr.c

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14

fs/nfsd/nfsfh.h

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