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Subject[095/262] nfsd4: fix open downgrade, again
3.0-stable review patch.  If anyone has any objections, please let me know.

------------------

From: "J. Bruce Fields" <bfields@redhat.com>

commit 3d02fa29dec920c597dd7b7db608a4bc71f088ce upstream.

Yet another open-management regression:

- nfs4_file_downgrade() doesn't remove the BOTH access bit on
downgrade, so the server's idea of the stateid's access gets
out of sync with the client's. If we want to keep an O_RDWR
open in this case, we should do that in the file_put_access
logic rather than here.
- We forgot to convert v4 access to an open mode here.

This logic has proven too hard to get right. In the future we may
consider:
- reexamining the lock/openowner relationship (locks probably
don't really need to take their own references here).
- adding open upgrade/downgrade support to the vfs.
- removing the atomic operations. They're redundant as long as
this is all under some other lock.

Also, maybe some kind of additional static checking would help catch
O_/NFS4_SHARE_ACCESS confusion.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/nfsd/nfs4state.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)

--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -188,8 +188,15 @@ static void nfs4_file_put_fd(struct nfs4
static void __nfs4_file_put_access(struct nfs4_file *fp, int oflag)
{
if (atomic_dec_and_test(&fp->fi_access[oflag])) {
- nfs4_file_put_fd(fp, O_RDWR);
nfs4_file_put_fd(fp, oflag);
+ /*
+ * It's also safe to get rid of the RDWR open *if*
+ * we no longer have need of the other kind of access
+ * or if we already have the other kind of open:
+ */
+ if (fp->fi_fds[1-oflag]
+ || atomic_read(&fp->fi_access[1 - oflag]) == 0)
+ nfs4_file_put_fd(fp, O_RDWR);
}
}

@@ -3381,8 +3388,9 @@ static inline void nfs4_file_downgrade(s
int i;

for (i = 1; i < 4; i++) {
- if (test_bit(i, &stp->st_access_bmap) && !(i & to_access)) {
- nfs4_file_put_access(stp->st_file, i);
+ if (test_bit(i, &stp->st_access_bmap)
+ && ((i & to_access) != i)) {
+ nfs4_file_put_access(stp->st_file, nfs4_access_to_omode(i));
__clear_bit(i, &stp->st_access_bmap);
}
}



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