nfsd4: fix open downgrade, again (3d02fa29) · Commits · 戴 / test

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. Cc: stable@kernel.org Signed-off-by:

J. Bruce Fields <bfields@redhat.com>

fs/nfsd/nfs4state.c

+11 −3

Original line number	Diff line number	Diff line
		@@ -194,8 +194,15 @@ static void nfs4_file_put_fd(struct nfs4_file *fp, int oflag)
		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);
		}
		}

		@@ -3500,8 +3507,9 @@ static inline void nfs4_file_downgrade(struct nfs4_ol_stateid *stp, unsigned int
		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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