[lustre-devel] [PATCH 1/2] staging: lustre: replace uses of class_devno_max by MAX_OBD_DEVICES
Aya Mahfouz
mahfouz.saif.elyazal at gmail.com
Fri Nov 4 01:37:36 PDT 2016
On Thu, Nov 3, 2016 at 1:05 AM, Dilger, Andreas <andreas.dilger at intel.com>
wrote:
> On Oct 25, 2016, at 10:47, Aya Mahfouz <mahfouz.saif.elyazal at gmail.com>
> wrote:
> >
> > On Mon, Oct 17, 2016 at 10:38:31PM +0000, Dilger, Andreas wrote:
> >> On Oct 17, 2016, at 15:46, Aya Mahfouz <mahfouz.saif.elyazal at gmail.com>
> wrote:
> >>>
> >>> class_devno_max is an inline function that returns
> >>> MAX_OBD_DEVICES. Replace all calls to the function
> >>> by MAX_OBD_DEVICES.
> >>
> >> Thanks for your patch, but unfortunately it can't be accepted.
> >>
> >> This function was added in preparation of being able to tune the maximum
> >> number of storage devices dynamically, rather than having to hard code
> it
> >> to the maximum possible number of servers that a client can possibly
> >> connect to.
> >>
> >> While the current maximum of 8192 servers has been enough for current
> >> filesystems, I'd rather move in the direction of dynamically handling
> this
> >> limit rather than re-introducing a hard-coded constant throughout the
> code.
> >>
> > Hello,
> >
> > I would like to proceed with implementing the function if possible.
> > Kindly direct me to some starting pointers.
>
> Hi Aya,
> thanks for offering to look into this.
>
> There are several ways to approach this problem to make the allocation
> of the obd_devs[] array dynamic. In most cases, there isn't any value
> to dynamically shrink this array, since the filesystem(s) will typically
> be mounted until the node is rebooted, and it is only in the tens of KB
> size range, so this will not affect ongoing operations, and that simplifies
> the implementation.
>
> The easiest way would be to have a dynamically-sized obd_devs[] array that
> is reallocated in class_newdev() in PAGE_SIZE chunks whenever the current
> array has no more free slots and copied to the new array, using
> obd_dev_lock
> to protect the array while it is being reallocated and copied. In most
> cases, this would save memory over the static array (not many filesystems
> have so many servers), but for the few sites that have 10000+ servers they
> don't need to change the source to handle this. Using libcfs_kvzalloc()
> would avoid issues with allocating large chunks of memory.
>
> There are a few places where obd_devs[] is accessed outside obd_dev_lock
> that would need to be fixed now that this array may be changed at runtime.
>
> A second approach that may scale better is to change obd_devs from an array
> to a doubly linked list (using standard list_head helpers). In many cases
> the whole list is seached linearly, and most of the uses of class_num2obd()
> are just used to walk that list in order, which could be replaced with
> list_for_each_entry() list traversal. The class_name2dev() function should
> be changed to return the pointer to the obd_device structure, and a new
> helper class_dev2num() would just return the obd_minor number from the
> obd_device struct for the one use in class_resolve_dev_name(). Using a
> linked list has the advantage that there is no need to search for free
> slots
> in the array, since devices would be removed from the list when it is
> freed.
>
> Cheers, Andreas
>
> Thanks Andreas! Will start looking into it.
--
Kind Regards,
Aya Saif El-yazal Mahfouz
> >> One comment inline below, if you still want to submit a patch.
> >>
> >>> Signed-off-by: Aya Mahfouz <mahfouz.saif.elyazal at gmail.com>
> >>> ---
> >>> drivers/staging/lustre/lustre/obdclass/class_obd.c | 6 +++---
> >>> drivers/staging/lustre/lustre/obdclass/genops.c | 22
> +++++++++++-----------
> >>> .../lustre/lustre/obdclass/linux/linux-module.c | 6 +++---
> >>> 3 files changed, 17 insertions(+), 17 deletions(-)
> >>>
> >>> diff --git a/drivers/staging/lustre/lustre/obdclass/class_obd.c
> b/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >>> index 2b21675..b775c74 100644
> >>> --- a/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >>> +++ b/drivers/staging/lustre/lustre/obdclass/class_obd.c
> >>> @@ -345,7 +345,7 @@ int class_handle_ioctl(unsigned int cmd, unsigned
> long arg)
> >>> goto out;
> >>> }
> >>> obd = class_name2obd(data->ioc_inlbuf4);
> >>> - } else if (data->ioc_dev < class_devno_max()) {
> >>> + } else if (data->ioc_dev < MAX_OBD_DEVICES) {
> >>> obd = class_num2obd(data->ioc_dev);
> >>> } else {
> >>> CERROR("OBD ioctl: No device\n");
> >>> @@ -498,7 +498,7 @@ static int __init obdclass_init(void)
> >>> }
> >>>
> >>> /* This struct is already zeroed for us (static global) */
> >>> - for (i = 0; i < class_devno_max(); i++)
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++)
> >>> obd_devs[i] = NULL;
> >>
> >> This block can just be removed entirely. It used to do something
> useful,
> >> but through a series of changes it has become useless.
> >>
> >> Cheers, Andreas
> >>
> >>> /* Default the dirty page cache cap to 1/2 of system memory.
> >>> @@ -548,7 +548,7 @@ static void obdclass_exit(void)
> >>> lustre_unregister_fs();
> >>>
> >>> misc_deregister(&obd_psdev);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (obd && obd->obd_set_up &&
> >>> diff --git a/drivers/staging/lustre/lustre/obdclass/genops.c
> b/drivers/staging/lustre/lustre/obdclass/genops.c
> >>> index 99c2da6..af4fc58 100644
> >>> --- a/drivers/staging/lustre/lustre/obdclass/genops.c
> >>> +++ b/drivers/staging/lustre/lustre/obdclass/genops.c
> >>> @@ -290,7 +290,7 @@ struct obd_device *class_newdev(const char
> *type_name, const char *name)
> >>> LASSERT(newdev->obd_magic == OBD_DEVICE_MAGIC);
> >>>
> >>> write_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (obd && (strcmp(name, obd->obd_name) == 0)) {
> >>> @@ -322,9 +322,9 @@ struct obd_device *class_newdev(const char
> *type_name, const char *name)
> >>> }
> >>> write_unlock(&obd_dev_lock);
> >>>
> >>> - if (!result && i >= class_devno_max()) {
> >>> + if (!result && i >= MAX_OBD_DEVICES) {
> >>> CERROR("all %u OBD devices used, increase
> MAX_OBD_DEVICES\n",
> >>> - class_devno_max());
> >>> + MAX_OBD_DEVICES);
> >>> result = ERR_PTR(-EOVERFLOW);
> >>> goto out;
> >>> }
> >>> @@ -372,7 +372,7 @@ int class_name2dev(const char *name)
> >>> return -1;
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (obd && strcmp(name, obd->obd_name) == 0) {
> >>> @@ -397,7 +397,7 @@ struct obd_device *class_name2obd(const char *name)
> >>> {
> >>> int dev = class_name2dev(name);
> >>>
> >>> - if (dev < 0 || dev > class_devno_max())
> >>> + if (dev < 0 || dev > MAX_OBD_DEVICES)
> >>> return NULL;
> >>> return class_num2obd(dev);
> >>> }
> >>> @@ -408,7 +408,7 @@ int class_uuid2dev(struct obd_uuid *uuid)
> >>> int i;
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (obd && obd_uuid_equals(uuid, &obd->obd_uuid)) {
> >>> @@ -435,7 +435,7 @@ struct obd_device *class_num2obd(int num)
> >>> {
> >>> struct obd_device *obd = NULL;
> >>>
> >>> - if (num < class_devno_max()) {
> >>> + if (num < MAX_OBD_DEVICES) {
> >>> obd = obd_devs[num];
> >>> if (!obd)
> >>> return NULL;
> >>> @@ -463,7 +463,7 @@ struct obd_device *class_find_client_obd(struct
> obd_uuid *tgt_uuid,
> >>> int i;
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (!obd)
> >>> @@ -496,13 +496,13 @@ struct obd_device *class_devices_in_group(struct
> obd_uuid *grp_uuid, int *next)
> >>>
> >>> if (!next)
> >>> i = 0;
> >>> - else if (*next >= 0 && *next < class_devno_max())
> >>> + else if (*next >= 0 && *next < MAX_OBD_DEVICES)
> >>> i = *next;
> >>> else
> >>> return NULL;
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (; i < class_devno_max(); i++) {
> >>> + for (; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd = class_num2obd(i);
> >>>
> >>> if (!obd)
> >>> @@ -533,7 +533,7 @@ int class_notify_sptlrpc_conf(const char *fsname,
> int namelen)
> >>> LASSERT(namelen > 0);
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> obd = class_num2obd(i);
> >>>
> >>> if (!obd || obd->obd_set_up == 0 || obd->obd_stopping)
> >>> diff --git a/drivers/staging/lustre/lustre/obdclass/linux/linux-module.c
> b/drivers/staging/lustre/lustre/obdclass/linux/linux-module.c
> >>> index 33342bf..ca5b466 100644
> >>> --- a/drivers/staging/lustre/lustre/obdclass/linux/linux-module.c
> >>> +++ b/drivers/staging/lustre/lustre/obdclass/linux/linux-module.c
> >>> @@ -228,7 +228,7 @@ static ssize_t health_show(struct kobject *kobj,
> struct attribute *attr,
> >>> return sprintf(buf, "LBUG\n");
> >>>
> >>> read_lock(&obd_dev_lock);
> >>> - for (i = 0; i < class_devno_max(); i++) {
> >>> + for (i = 0; i < MAX_OBD_DEVICES; i++) {
> >>> struct obd_device *obd;
> >>>
> >>> obd = class_num2obd(i);
> >>> @@ -326,7 +326,7 @@ static struct attribute *lustre_attrs[] = {
> >>>
> >>> static void *obd_device_list_seq_start(struct seq_file *p, loff_t
> *pos)
> >>> {
> >>> - if (*pos >= class_devno_max())
> >>> + if (*pos >= MAX_OBD_DEVICES)
> >>> return NULL;
> >>>
> >>> return pos;
> >>> @@ -339,7 +339,7 @@ static void obd_device_list_seq_stop(struct
> seq_file *p, void *v)
> >>> static void *obd_device_list_seq_next(struct seq_file *p, void *v,
> loff_t *pos)
> >>> {
> >>> ++*pos;
> >>> - if (*pos >= class_devno_max())
> >>> + if (*pos >= MAX_OBD_DEVICES)
> >>> return NULL;
> >>>
> >>> return pos;
> >>> --
> >>> 2.5.0
> >>>
> >>>
> >>> --
> >>> Kind Regards,
> >>> Aya Saif El-yazal Mahfouz
> >>> _______________________________________________
> >>> lustre-devel mailing list
> >>> lustre-devel at lists.lustre.org
> >>> http://lists.lustre.org/listinfo.cgi/lustre-devel-lustre.org
> >>
> >
> > --
> > Kind Regards,
> > Aya Saif El-yazal Mahfouz
> > _______________________________________________
> > lustre-devel mailing list
> > lustre-devel at lists.lustre.org
> > http://lists.lustre.org/listinfo.cgi/lustre-devel-lustre.org
>
>
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