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raid5-ppl: PPL support for disks with write-back cache enabled

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In order to provide data consistency with PPL for disks with write-back
cache enabled all data has to be flushed to disks before next PPL
entry. The disks to be flushed are marked in the bitmap. It's modified
under a mutex and it's only read after PPL io unit is submitted.

A limitation of 64 disks in the array has been introduced to keep data
structures and implementation simple. RAID5 arrays with so many disks are
not likely due to high risk of multiple disks failure. Such restriction
should not be a real life limitation.

With write-back cache disabled next PPL entry is submitted when data write
for current one completes. Data flush defers next log submission so trigger
it when there are no stripes for handling found.

As PPL assures all data is flushed to disk at request completion, just
acknowledge flush request when PPL is enabled.

Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Signed-off-by: Shaohua Li <sh.li@alibaba-inc.com>
This commit is contained in:
Tomasz Majchrzak
2017-12-27 10:31:40 +01:00
committed by Shaohua Li
parent 92e6245dea
commit 1532d9e87e
7 changed files with 195 additions and 25 deletions
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5
drivers/md/md.c
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@@ -711,7 +711,7 @@ static struct md_rdev *find_rdev(struct mddev *mddev, dev_t dev)
return NULL;
}
static struct md_rdev *find_rdev_rcu(struct mddev *mddev, dev_t dev)
struct md_rdev *md_find_rdev_rcu(struct mddev *mddev, dev_t dev)
{
struct md_rdev *rdev;
@@ -721,6 +721,7 @@ static struct md_rdev *find_rdev_rcu(struct mddev *mddev, dev_t dev)
return NULL;
}
EXPORT_SYMBOL_GPL(md_find_rdev_rcu);
static struct md_personality *find_pers(int level, char *clevel)
{
@@ -7010,7 +7011,7 @@ static int set_disk_faulty(struct mddev *mddev, dev_t dev)
return -ENODEV;
rcu_read_lock();
rdev = find_rdev_rcu(mddev, dev);
rdev = md_find_rdev_rcu(mddev, dev);
if (!rdev)
err = -ENODEV;
else {