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authorLarry Chen <lchen@suse.com>2018-06-08 02:04:43 +0200
committerLinus Torvalds <torvalds@linux-foundation.org>2018-06-08 02:34:33 +0200
commit133b81f28edebfd9b20486351589e460e8c052e4 (patch)
tree63a5684bf45ad13498e7122a20f9136843439d46 /fs/ocfs2/dlmglue.h
parentocfs2: clean up redundant function declarations (diff)
downloadlinux-133b81f28edebfd9b20486351589e460e8c052e4.tar.xz
linux-133b81f28edebfd9b20486351589e460e8c052e4.zip
ocfs2: ocfs2_inode_lock_tracker does not distinguish lock level
ocfs2_inode_lock_tracker as a variant of ocfs2_inode_lock, is used to prevent deadlock due to recursive lock acquisition. But this function does not distinguish whether the requested level is EX or PR. If a RP lock has been attained, this function will immediately return success afterwards even an EX lock is requested. But actually the return value does not mean that the process got a EX lock, because ocfs2_inode_lock has not been called. When taking lock levels into account, we face some different situations: 1. no lock is held In this case, just lock the inode and return 0 2. We are holding a lock For this situation, things diverges into several cases wanted holding what to do ex ex see 2.1 below ex pr see 2.2 below pr ex see 2.1 below pr pr see 2.1 below 2.1 lock level that is been held is compatible with the wanted level, so no lock action will be tacken. 2.2 Otherwise, an upgrade is needed, but it is forbidden. Reason why upgrade within a process is forbidden is that lock upgrade may cause dead lock. The following illustrate how it happens. process 1 process 2 ocfs2_inode_lock_tracker(ex=0) <====== ocfs2_inode_lock_tracker(ex=1) ocfs2_inode_lock_tracker(ex=1) For the status quo of ocfs2, without this patch, neither a bug nor end-user impact will be caused because the wrong logic is avoided. But I'm afraid this generic interface, may be called by other developers in future and used in this situation. a process ocfs2_inode_lock_tracker(ex=0) ocfs2_inode_lock_tracker(ex=1) Link: http://lkml.kernel.org/r/20180510053230.17217-1-lchen@suse.com Signed-off-by: Larry Chen <lchen@suse.com> Reviewed-by: Gang He <ghe@suse.com> Cc: Mark Fasheh <mark@fasheh.com> Cc: Joel Becker <jlbec@evilplan.org> Cc: Junxiao Bi <junxiao.bi@oracle.com> Cc: Joseph Qi <jiangqi903@gmail.com> Cc: Changwei Ge <ge.changwei@h3c.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/ocfs2/dlmglue.h')
-rw-r--r--fs/ocfs2/dlmglue.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/fs/ocfs2/dlmglue.h b/fs/ocfs2/dlmglue.h
index 256e0a9067b8..4ec1c828f6e0 100644
--- a/fs/ocfs2/dlmglue.h
+++ b/fs/ocfs2/dlmglue.h
@@ -96,6 +96,7 @@ struct ocfs2_trim_fs_info {
struct ocfs2_lock_holder {
struct list_head oh_list;
struct pid *oh_owner_pid;
+ int oh_ex;
};
/* ocfs2_inode_lock_full() 'arg_flags' flags */