Currently, all glock holders in the "glocks" dump file are reported as being associated with the process that acquired them, even for holders that are actually associated with the filesystem itself (like the journal glock holder) or with cached inodes (like iopen and flock glock holders). This is confusing when those holders outlive the processes that have acquired them, and it trips up utilities that analyze lock dependencies. For example, the following two glocks were acquired by pid 10821 during the initial mount, which has since terminated: G: s:EX n:9/0 f:qb t:EX d:EX/0 a:0 v:0 r:3 m:200 p:0 H: s:EX f:ecH e:0 p:10821 [(ended)] init_inodes+0x5c2/0xb10 [gfs2] G: s:EX n:2/805f f:qob t:EX d:EX/0 a:0 v:0 r:4 m:200 p:1 H: s:EX f:H e:0 p:10821 [(ended)] gfs2_fill_super+0x92b/0xcc0 [gfs2] I: n:6/32863 t:8 f:0x00 d:0x00000201 s:24 p:0 This patch queue tries to fix this problem in two ways: * Glock holders which are not held by the process that acquired them are marked as GL_NOPID. For those holders, the PID is reported as 0, and the process name is reported as "(none)". * With this change alone, we would have a much harder time detecting locking cycles involving iopen or flock glocks: in both cases, a process which has a file descriptor open depends on the iopen and flock glock of the corresponding inode / file. To keep track of these dependencies, we introduce a new "glockfd" dump file that reports which file descriptors of which processes are holding which glocks. A utility that checks for locking problems using this additional information is forthcoming, but hasn't been completed so far. NEW EXPORTS This patch queue requires iterating through all file descriptors of all processes, which is made easier by exporting find_ge_pid() and task_lookup_next_fd_rcu(); copying Eric W. Biederman and the linux-kernel and linux-fsdevel lists to make sure that's okay. Thanks, Andreas Andreas Gruenbacher (5): gfs2: Add glockfd debugfs file gfs2: Add flocks to glockfd debugfs file gfs2: Add GL_NOPID flag for process-independent glock holders gfs2: Mark flock glock holders as GL_NOPID gfs2: Mark the remaining process-independent glock holders as GL_NOPID fs/file.c | 1 + fs/gfs2/file.c | 29 +++++- fs/gfs2/glock.c | 211 +++++++++++++++++++++++++++++++++++++++++-- fs/gfs2/glock.h | 1 + fs/gfs2/inode.c | 6 +- fs/gfs2/ops_fstype.c | 14 +-- fs/gfs2/super.c | 3 +- fs/gfs2/util.c | 6 +- kernel/pid.c | 1 + 9 files changed, 247 insertions(+), 25 deletions(-) -- 2.35.1
