kernel/git/stable/linux.git/drivers/md/dm-round-robin.c, branch master

dm: rename multipath path selector source files to have "dm-ps" prefix

2020-12-04T23:04:35+00:00

Additional prefix helps clarify that these source files implement path selectors. Required updating Makefile to still build modules _without_ the "dm-ps" prefix to preserve dm-multipath's ability to autoload path selector modules. While at it, cleaned up some DM whitespace in Makefile. Signed-off-by: Mike Snitzer

dm round robin: revert "use percpu 'repeat_count' and 'current_path'"

2017-02-17T05:54:09+00:00

The sloppy nature of lockless access to percpu pointers (s->current_path) in rr_select_path(), from multiple threads, is causing some paths to used more than others -- which results in less IO performance being observed. Revert these upstream commits to restore truly symmetric round-robin IO submission in DM multipath: b0b477c dm round robin: use percpu 'repeat_count' and 'current_path' 802934b dm round robin: do not use this_cpu_ptr() without having preemption disabled There is no benefit to all this complexity if repeat_count = 1 (which is the recommended default). Cc: stable@vger.kernel.org # 4.6+ Signed-off-by: Mike Snitzer

dm round robin: do not use this_cpu_ptr() without having preemption disabled

2016-08-15T13:23:14+00:00

Use local_irq_save() to disable preemption before calling this_cpu_ptr(). Reported-by: Benjamin Block Fixes: b0b477c7e0dd ("dm round robin: use percpu 'repeat_count' and 'current_path'") Cc: stable@vger.kernel.org # 4.6+ Suggested-by: Jens Axboe Signed-off-by: Mike Snitzer

dm round robin: use percpu 'repeat_count' and 'current_path'

2016-02-23T03:34:42+00:00

Now that dm-mpath core is lockless in the per-IO fast path it is critical, for performance, to have the .select_path hook (rr_select_path) also be as lockless as possible. The new percpu members of 'struct selector' allow for lockless support of 'repeat_count' governed repeat use of a previously selected path. If a path fails while it is 'current_path' the worst case is concurrent IO might be mapped to the failed path until the .fail_path hook (rr_fail_path) is called. Signed-off-by: Mike Snitzer

dm path selector: remove 'repeat_count' return from .select_path hook

2016-02-23T03:34:42+00:00

If a path selector has any use for a repeat_count it should be handled locally and not depend on the dm-mpath core to be concerned with it. Signed-off-by: Mike Snitzer

dm mpath: push path selector locking down to path selectors

2016-02-23T03:34:41+00:00

Proper locking of the lists used by the path selectors should be handled within the selectors (relying on dm-mpath.c code's use of the m->lock spinlock was reckless). Signed-off-by: Mike Snitzer

dm mpath: remove repeat_count support from multipath core

2016-02-23T03:34:40+00:00

Preparation for making __multipath_map() avoid taking the m->lock spinlock -- in favor of using RCU locking. repeat_count was primarily for bio-based DM multipath's benefit. There is really no need for it anymore now that DM multipath is request-based. As such, repeat_count > 1 is no longer honored and a warning is displayed if the user attempts to use a value > 1. This is a temporary change for the round-robin path-selector (as a later commit will restore its support for repeat_count > 1). Signed-off-by: Mike Snitzer

dm: reject trailing characters in sccanf input

2012-03-28T17:41:26+00:00

Device mapper uses sscanf to convert arguments to numbers. The problem is that the way we use it ignores additional unmatched characters in the scanned string. For example, this `if (sscanf(string, "%d", &number) == 1)' will match a number, but also it will match number with some garbage appended, like "123abc". As a result, device mapper accepts garbage after some numbers. For example the command `dmsetup create vg1-new --table "0 16384 linear 254:1bla 34816bla"' will pass without an error. This patch fixes all sscanf uses in device mapper. It appends "%c" with a pointer to a dummy character variable to every sscanf statement. The construct `if (sscanf(string, "%d%c", &number, &dummy) == 1)' succeeds only if string is a null-terminated number (optionally preceded by some whitespace characters). If there is some character appended after the number, sscanf matches "%c", writes the character to the dummy variable and returns 2. We check the return value for 1 and consequently reject numbers with some garbage appended. Signed-off-by: Mikulas Patocka Acked-by: Mike Snitzer Signed-off-by: Alasdair G Kergon

md: Add module.h to all files using it implicitly

2011-10-31T23:31:18+00:00

A pending cleanup will mean that module.h won't be implicitly everywhere anymore. Make sure the modular drivers in md dir are actually calling out for explicitly in advance. Signed-off-by: Paul Gortmaker

dm mpath: add start_io and nr_bytes to path selectors

2009-06-22T09:12:27+00:00

This patch makes two additions to the dm path selector interface for dynamic load balancers: o a new hook, start_io() o a new parameter 'nr_bytes' to select_path()/start_io()/end_io() to pass the size of the I/O start_io() is called when a target driver actually submits I/O to the selected path. Path selectors can use it to start accounting of the I/O. (e.g. counting the number of in-flight I/Os.) The start_io hook is based on the patch posted by Stefan Bader: https://www.redhat.com/archives/dm-devel/2005-October/msg00050.html nr_bytes, the size of the I/O, is so path selectors can take the size of the I/O into account when deciding which path to use. dm-service-time uses it to estimate service time, for example. (Added the nr_bytes member to dm_mpath_io instead of using existing details.bi_size, since request-based dm patch deletes it.) Signed-off-by: Stefan Bader Signed-off-by: Kiyoshi Ueda Signed-off-by: Jun'ichi Nomura Signed-off-by: Alasdair G Kergon