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Code Releases Activity

pvcreate,pvremove: fix reacquiring global lock after prompt

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When pvcreate/pvremove prompt the user, they first release
the global lock, then acquire it again after the prompt,
to avoid blocking other commands while waiting for a user
response.  This release/reacquire changes the locking
order with respect to the hints flock (and potentially other
locks).  So, to avoid deadlock, use a nonblocking request
when reacquiring the global lock.
This commit is contained in:
David Teigland 2019-11-26 14:34:43 -06:00
parent 1c9b36618e
commit 2037476008
4 changed files with 16 additions and 6 deletions
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14
lib/locking/locking.c
View File

@ -338,7 +338,7 @@ int sync_local_dev_names(struct cmd_context* cmd)
* an explicitly acquired ex global lock to sh in process_each. * an explicitly acquired ex global lock to sh in process_each.
*/ */
static int _lockf_global(struct cmd_context *cmd, const char *mode, int convert) static int _lockf_global(struct cmd_context *cmd, const char *mode, int convert, int nonblock)
{ {
uint32_t flags = 0; uint32_t flags = 0;
int ret; int ret;
@ -346,6 +346,9 @@ static int _lockf_global(struct cmd_context *cmd, const char *mode, int convert)
if (convert) if (convert)
flags |= LCK_CONVERT; flags |= LCK_CONVERT;
if (nonblock)
flags |= LCK_NONBLOCK;
if (!strcmp(mode, "ex")) { if (!strcmp(mode, "ex")) {
flags |= LCK_WRITE; flags |= LCK_WRITE;
@ -379,7 +382,7 @@ static int _lockf_global(struct cmd_context *cmd, const char *mode, int convert)
int lockf_global(struct cmd_context *cmd, const char *mode) int lockf_global(struct cmd_context *cmd, const char *mode)
{ {
return _lockf_global(cmd, mode, 0); return _lockf_global(cmd, mode, 0, 0);
} }
int lockf_global_convert(struct cmd_context *cmd, const char *mode) int lockf_global_convert(struct cmd_context *cmd, const char *mode)
@ -388,7 +391,12 @@ int lockf_global_convert(struct cmd_context *cmd, const char *mode)
if (cmd->lockf_global_ex && !strcmp(mode, "ex")) if (cmd->lockf_global_ex && !strcmp(mode, "ex"))
return 1; return 1;
return _lockf_global(cmd, mode, 1); return _lockf_global(cmd, mode, 1, 0);
}
int lockf_global_nonblock(struct cmd_context *cmd, const char *mode)
{
return _lockf_global(cmd, mode, 0, 1);
} }
int lock_global(struct cmd_context *cmd, const char *mode) int lock_global(struct cmd_context *cmd, const char *mode)

1
lib/locking/locking.h
View File

@ -75,6 +75,7 @@ int activate_lvs(struct cmd_context *cmd, struct dm_list *lvs, unsigned exclusiv
int lockf_global(struct cmd_context *cmd, const char *mode); int lockf_global(struct cmd_context *cmd, const char *mode);
int lockf_global_convert(struct cmd_context *cmd, const char *mode); int lockf_global_convert(struct cmd_context *cmd, const char *mode);
int lockf_global_nonblock(struct cmd_context *cmd, const char *mode);
int lock_global(struct cmd_context *cmd, const char *mode); int lock_global(struct cmd_context *cmd, const char *mode);
int lock_global_convert(struct cmd_context *cmd, const char *mode); int lock_global_convert(struct cmd_context *cmd, const char *mode);

2
lib/misc/lvm-flock.c
View File

@ -164,7 +164,7 @@ static int _do_write_priority_flock(const char *file, int *fd, int operation, ui
strcpy(file_aux, file); strcpy(file_aux, file);
strcat(file_aux, AUX_LOCK_SUFFIX); strcat(file_aux, AUX_LOCK_SUFFIX);
if ((r = _do_flock(file_aux, &fd_aux, LOCK_EX, 0))) { if ((r = _do_flock(file_aux, &fd_aux, LOCK_EX, nonblock))) {
if (operation == LOCK_EX) { if (operation == LOCK_EX) {
r = _do_flock(file, fd, operation, nonblock); r = _do_flock(file, fd, operation, nonblock);
_undo_flock(file_aux, fd_aux); _undo_flock(file_aux, fd_aux);

5
tools/toollib.c
View File

@ -5577,10 +5577,11 @@ int pvcreate_each_device(struct cmd_context *cmd,
* Reacquire the lock that was released above before waiting, then * Reacquire the lock that was released above before waiting, then
* check again that the devices can still be used. If the second loop * check again that the devices can still be used. If the second loop
* finds them changed, or can't find them any more, then they aren't * finds them changed, or can't find them any more, then they aren't
* used. * used. Use a non-blocking request when reacquiring to avoid
* potential deadlock since this is not the normal locking sequence.
*/ */
if (!lockf_global(cmd, "ex")) { if (!lockf_global_nonblock(cmd, "ex")) {
log_error("Failed to reacquire global lock after prompt."); log_error("Failed to reacquire global lock after prompt.");
goto_out; goto_out;
} }