On 02/07/2017 10:49 PM, Shaohua Li wrote:
> On Mon, Jan 30, 2017 at 07:59:50PM +0100, Artur Paszkiewicz wrote:
>> Add 'consistency_policy' attribute for array. It indicates how the array
>> maintains consistency in case of unexpected shutdown.
>>
>> Add 'ppl_sector' and 'ppl_size' for rdev, which describe the location
>> and size of the PPL space on the device.
>>
>> These attributes are writable to allow enabling PPL for external
>> metadata arrays and (later) to enable/disable PPL for a running array.
>>
>> Signed-off-by: Artur Paszkiewicz <artur.paszkiewicz@xxxxxxxxx>
>> ---
>> Documentation/admin-guide/md.rst | 32 ++++++++++-
>> drivers/md/md.c | 115 +++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 144 insertions(+), 3 deletions(-)
>>
>> diff --git a/Documentation/admin-guide/md.rst b/Documentation/admin-guide/md.rst
>> index 7104ef757e73..2c153b3d798f 100644
>> --- a/Documentation/admin-guide/md.rst
>> +++ b/Documentation/admin-guide/md.rst
>> @@ -329,14 +329,14 @@ All md devices contain:
>> array creation it will default to 0, though starting the array as
>> ``clean`` will set it much larger.
>>
>> - new_dev
>> + new_dev
>> This file can be written but not read. The value written should
>> be a block device number as major:minor. e.g. 8:0
>> This will cause that device to be attached to the array, if it is
>> available. It will then appear at md/dev-XXX (depending on the
>> name of the device) and further configuration is then possible.
>>
>> - safe_mode_delay
>> + safe_mode_delay
>> When an md array has seen no write requests for a certain period
>> of time, it will be marked as ``clean``. When another write
>> request arrives, the array is marked as ``dirty`` before the write
>> @@ -345,7 +345,7 @@ All md devices contain:
>> period as a number of seconds. The default is 200msec (0.200).
>> Writing a value of 0 disables safemode.
>>
>> - array_state
>> + array_state
>> This file contains a single word which describes the current
>> state of the array. In many cases, the state can be set by
>> writing the word for the desired state, however some states
>> @@ -454,7 +454,30 @@ All md devices contain:
>> once the array becomes non-degraded, and this fact has been
>> recorded in the metadata.
>>
>> + consistency_policy
>> + This indicates how the array maintains consistency in case of unexpected
>> + shutdown. It can be:
>>
>> + none
>> + Array has no redundancy information, e.g. raid0, linear.
>> +
>> + resync
>> + Full resync is performed and all redundancy is regenerated when the
>> + array is started after unclean shutdown.
>> +
>> + bitmap
>> + Resync assisted by a write-intent bitmap.
>> +
>> + journal
>> + For raid4/5/6, journal device is used to log transactions and replay
>> + after unclean shutdown.
>> +
>> + ppl
>> + For raid5 only, :ref:`ppl` is used to close the write hole and eliminate
>> + resync.
>> +
>> + The accepted values when writing to this file are ``ppl`` and ``resync``,
>> + used to enable and disable PPL.
>>
>>
>> As component devices are added to an md array, they appear in the ``md``
>> @@ -616,6 +639,9 @@ Each directory contains:
>> adds bad blocks without acknowledging them. This is largely
>> for testing.
>>
>> + ppl_sector, ppl_size
>> + Location and size (in sectors) of the space used for Partial Parity Log
>> + on this device.
>>
>>
>> An active md device will also contain an entry for each active device
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index e96f73572e23..47ab3afe87cb 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -3205,6 +3205,78 @@ static ssize_t ubb_store(struct md_rdev *rdev, const char *page, size_t len)
>> static struct rdev_sysfs_entry rdev_unack_bad_blocks =
>> __ATTR(unacknowledged_bad_blocks, S_IRUGO|S_IWUSR, ubb_show, ubb_store);
>>
>> +static ssize_t
>> +ppl_sector_show(struct md_rdev *rdev, char *page)
>> +{
>> + return sprintf(page, "%llu\n", (unsigned long long)rdev->ppl.sector);
>> +}
>> +
>> +static ssize_t
>> +ppl_sector_store(struct md_rdev *rdev, const char *buf, size_t len)
>> +{
>> + unsigned long long sector;
>> +
>> + if (kstrtoull(buf, 10, §or) < 0)
>> + return -EINVAL;
>> + if (sector != (sector_t)sector)
>> + return -EINVAL;
>> +
>> + if (rdev->mddev->pers && test_bit(MD_HAS_PPL, &rdev->mddev->flags) &&
>> + rdev->raid_disk >= 0)
>> + return -EBUSY;
>> +
>> + if (rdev->mddev->persistent) {
>> + if (rdev->mddev->major_version == 0)
>> + return -EINVAL;
>> + if ((sector > rdev->sb_start &&
>> + sector - rdev->sb_start > S16_MAX) ||
>> + (sector < rdev->sb_start &&
>> + rdev->sb_start - sector > -S16_MIN))
>> + return -EINVAL;
>> + rdev->ppl.offset = sector - rdev->sb_start;
>
> Why do we allow non-external array changes the ppl log position and size?
To support enabling ppl for a running array. Mdadm should not change the
metadata if the array is running, so we can't read the ppl position and
size from the superblock. This is similar to adding an internal bitmap
with mdadm --grow --bitmap=internal - mdadm writes the bitmap offset to
"bitmap/location" in sysfs.
>> + } else if (!rdev->mddev->external) {
>> + return -EBUSY;
>> + }
>> + rdev->ppl.sector = sector;
>> + return len;
>> +}
>> +
>> +static struct rdev_sysfs_entry rdev_ppl_sector =
>> +__ATTR(ppl_sector, S_IRUGO|S_IWUSR, ppl_sector_show, ppl_sector_store);
>> +
>> +static ssize_t
>> +ppl_size_show(struct md_rdev *rdev, char *page)
>> +{
>> + return sprintf(page, "%u\n", rdev->ppl.size);
>> +}
>> +
>> +static ssize_t
>> +ppl_size_store(struct md_rdev *rdev, const char *buf, size_t len)
>> +{
>> + unsigned int size;
>> +
>> + if (kstrtouint(buf, 10, &size) < 0)
>> + return -EINVAL;
>> +
>> + if (rdev->mddev->pers && test_bit(MD_HAS_PPL, &rdev->mddev->flags) &&
>> + rdev->raid_disk >= 0)
>> + return -EBUSY;
>> +
>> + if (rdev->mddev->persistent) {
>> + if (rdev->mddev->major_version == 0)
>> + return -EINVAL;
>> + if (size > U16_MAX)
>> + return -EINVAL;
>> + } else if (!rdev->mddev->external) {
>> + return -EBUSY;
>> + }
>> + rdev->ppl.size = size;
>> + return len;
>> +}
>> +
>> +static struct rdev_sysfs_entry rdev_ppl_size =
>> +__ATTR(ppl_size, S_IRUGO|S_IWUSR, ppl_size_show, ppl_size_store);
>> +
>> static struct attribute *rdev_default_attrs[] = {
>> &rdev_state.attr,
>> &rdev_errors.attr,
>> @@ -3215,6 +3287,8 @@ static struct attribute *rdev_default_attrs[] = {
>> &rdev_recovery_start.attr,
>> &rdev_bad_blocks.attr,
>> &rdev_unack_bad_blocks.attr,
>> + &rdev_ppl_sector.attr,
>> + &rdev_ppl_size.attr,
>> NULL,
>> };
>> static ssize_t
>> @@ -4951,6 +5025,46 @@ static struct md_sysfs_entry md_array_size =
>> __ATTR(array_size, S_IRUGO|S_IWUSR, array_size_show,
>> array_size_store);
>>
>> +static ssize_t
>> +consistency_policy_show(struct mddev *mddev, char *page)
>> +{
>> + int ret;
>> +
>> + if (test_bit(MD_HAS_JOURNAL, &mddev->flags)) {
>> + ret = sprintf(page, "journal\n");
>> + } else if (test_bit(MD_HAS_PPL, &mddev->flags)) {
>> + ret = sprintf(page, "ppl\n");
>> + } else if (mddev->bitmap) {
>> + ret = sprintf(page, "bitmap\n");
>> + } else if (mddev->pers) {
>> + if (mddev->pers->sync_request)
>> + ret = sprintf(page, "resync\n");
>> + else
>> + ret = sprintf(page, "none\n");
>> + } else {
>> + ret = sprintf(page, "unknown\n");
>> + }
>> +
>> + return ret;
>> +}
>> +
>> +static ssize_t
>> +consistency_policy_store(struct mddev *mddev, const char *buf, size_t len)
>> +{
>> + if (mddev->pers) {
>> + return -EBUSY;
>> + } else if (mddev->external && strncmp(buf, "ppl", 3) == 0) {
>> + set_bit(MD_HAS_PPL, &mddev->flags);
>> + return len;
>
> Here we should check if ppl position and size are valid before we set the flag.
>
> And shouldn't we move this part to .change_consistency_policy added in patch 9?
> This is a consistency policy change too.
Yes, but here the array is not started yet and we don't have the
personality for which to call .change_consistency_policy. We are not
changing the consistency policy here, but rather setting it initially
for an external metadata array.
Thanks,
Artur
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