Hi David,
This patch adds comments explaining the original design, and also adds
a cleanup so that a volume level error-handles for the flush failures
can be implemented. I wonder if you have any comments.?
(Also just a note, a bio prealloc (for flush) will make below ENOMEM
to go away, however the prealloc itself has to optimized based on the
barrier option. So in the long run I don't think below ENOMEM would remain.)
Thanks, Anand
On 04/25/2017 04:58 PM, Anand Jain wrote:
This adds comments to the flush error handling part of
the code, and hopes to maintain the same logic with a
framework which can be used to handle the errors at the
volume level.
Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
---
fs/btrfs/disk-io.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++----
fs/btrfs/volumes.h | 1 +
2 files changed, 55 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index eb1ee7b6f532..dafcb6bb2d5d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -3527,6 +3527,10 @@ static int write_dev_flush(struct btrfs_device *device, int wait)
if (wait) {
bio = device->flush_bio;
if (!bio)
+ /*
+ * This means the alloc has failed with ENOMEM, however
+ * here we return 0, as its not a device error.
+ */
return 0;
wait_for_completion(&device->flush_wait);
@@ -3566,6 +3570,33 @@ static int write_dev_flush(struct btrfs_device *device, int wait)
return 0;
}
+static int check_barrier_error(struct btrfs_fs_devices *fsdevs)
+{
+ int submit_flush_error = 0;
+ int dev_flush_error = 0;
+ struct btrfs_device *dev;
+
+ list_for_each_entry_rcu(dev, &fsdevs->devices, dev_list) {
+ if (!dev->bdev) {
+ submit_flush_error++;
+ dev_flush_error++;
+ continue;
+ }
+ if (dev->last_flush_error == ENOMEM)
+ submit_flush_error++;
+ if (dev->last_flush_error && dev->last_flush_error != ENOMEM)
+ dev_flush_error++;
+ }
+
+ if (submit_flush_error >
+ fsdevs->fs_info->num_tolerated_disk_barrier_failures ||
+ dev_flush_error >
+ fsdevs->fs_info->num_tolerated_disk_barrier_failures)
+ return -EIO;
+
+ return 0;
+}
+
/*
* send an empty flush down to each device in parallel,
* then wait for them
@@ -3593,6 +3624,7 @@ static int barrier_all_devices(struct btrfs_fs_info *info)
ret = write_dev_flush(dev, 0);
if (ret)
errors_send++;
+ dev->last_flush_error = ret;
}
/* wait for all the barriers */
@@ -3607,12 +3639,30 @@ static int barrier_all_devices(struct btrfs_fs_info *info)
continue;
ret = write_dev_flush(dev, 1);
- if (ret)
+ if (ret) {
+ dev->last_flush_error = ret;
errors_wait++;
+ }
+ }
+
+ /*
+ * Try hard in case of flush. Lets say, in RAID1 we have
+ * the following situation
+ * dev1: EIO dev2: ENOMEM
+ * this is not a fatal error as we hope to recover from
+ * ENOMEM in the next attempt to flush.
+ * But the following is considered as fatal
+ * dev1: ENOMEM dev2: ENOMEM
+ * dev1: bdev == NULL dev2: ENOMEM
+ */
+ if (errors_send || errors_wait) {
+ /*
+ * At some point we need the status of all disks
+ * to arrive at the volume status. So error checking
+ * is being pushed to a separate loop.
+ */
+ return check_barrier_error(info->fs_devices);
}
- if (errors_send > info->num_tolerated_disk_barrier_failures ||
- errors_wait > info->num_tolerated_disk_barrier_failures)
- return -EIO;
return 0;
}
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 59be81206dd7..9c09dcd96e5d 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -74,6 +74,7 @@ struct btrfs_device {
int missing;
int can_discard;
int is_tgtdev_for_dev_replace;
+ int last_flush_error;
#ifdef __BTRFS_NEED_DEVICE_DATA_ORDERED
seqcount_t data_seqcount;
--
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