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If a vnode is released asynchronously through areleasef(), it is possible for the user process to reuse the file descriptor before areleasef is called. When this happens, getf() will return a stale reference, any operations in the kernel on that file descriptor will fail (as it is closed) and the operations meant for that fd will never occur from userspace's perspective. We correct this by detecting this condition in getf(), doing a putf on the old file handle, updating the file descriptor and proceeding as if everything was fine. When the areleasef() is done, it will harmlessly decrement the reference counter on the Illumos file handle. Signed-off-by: Richard Yao <ryao@gentoo.org> Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #492
43 lines
1.7 KiB
C
43 lines
1.7 KiB
C
/*****************************************************************************\
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* Copyright (C) 2015 Cluster Inc.
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* Produced at ClusterHQ Inc (cf, DISCLAIMER).
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* Written by Richard Yao <richard.yao@clusterhq.com>.
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://zfsonlinux.org/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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\*****************************************************************************/
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#ifndef _SPL_USER_H
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#define _SPL_USER_H
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/*
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* We have uf_info_t for areleasef(). We implement areleasef() using a global
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* linked list of all open file descriptors with the task structs referenced,
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* so accessing the correct descriptor from areleasef() only requires knowing
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* about the Linux task_struct. Since this is internal to our compatibility
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* layer, we make it an opaque type.
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*
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* XXX: If the descriptor changes under us and we do not do a getf() between
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* the change and using it, we would get an incorrect reference.
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*/
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struct uf_info;
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typedef struct uf_info uf_info_t;
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#define P_FINFO(x) ((uf_info_t *)x)
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#endif /* SPL_USER_H */
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