-----Original Message-----
From: Williams, Dan J
Sent: Friday, November 05, 2010 7:01 AM
To: Czarnowska, Anna
Cc: Neil Brown; linux-raid@vger.kernel.org; Neubauer, Wojciech;
Ciechanowski, Ed; Labun, Marcin; Hawrylewicz Czarnowski, Przemyslaw
Subject: Re: [PATCH 15/17] Monitor: more accurate size check when
looking for spares

On 10/29/2010 7:26 AM, Czarnowska, Anna wrote:

quoted

 From 1e6de2b744115224be88da674e633c33934e5cb6 Mon Sep 17 00:00:00

2001

quoted

From: Anna Czarnowska<redacted>
Date: Wed, 27 Oct 2010 12:06:42 +0100
Subject: [PATCH 15/17] Monitor: more accurate size check when looking

for spares

quoted

Signed-off-by: Anna Czarnowska<redacted>
---
  Monitor.c     |   23 ++++++++++++++++++++++-
  mdadm.h       |    1 +
  super-intel.c |   32 ++++++++++++++++++++++++++++++++
  3 files changed, 55 insertions(+), 1 deletions(-)

diff --git a/Monitor.c b/Monitor.c
index aa2856e..efe36eb 100644
--- a/Monitor.c
+++ b/Monitor.c

@@ -766,6 +766,27 @@ unsigned long long

min_active_disk_size_in_array(struct state *st)

quoted

  	return min;
  }

+unsigned long long min_spare_size_required(struct state *st,
+					   struct supertype *sty)
+{
+	int fd;
+	unsigned long long rv = 0;
+
+	if (!sty)
+		return rv;
+	if (sty->ss->min_acceptable_spare_size) {
+		fd = open(st->devname, O_RDONLY);
+		if (fd<  0)
+			return 0;
+		sty->ss->load_super(sty, fd, st->devname);
+		close(fd);
+		rv = sty->ss->min_acceptable_spare_size(sty);
+		sty->ss->free_super(sty);
+	} else
+		rv = min_active_disk_size_in_array(st);
+	return rv;
+}
+
  struct state *get_parent(struct state *st)
  {
  	if (is_external(st->metadata_version))

@@ -892,7 +913,7 @@ static void spare_sharing(struct state

*statelist, char *mailaddr,

quoted

  			dprintf("no sra for device: %s\n", stp->devname);
  			continue;
  		}
-		min_size = min_active_disk_size_in_array(st);
+		min_size = min_spare_size_required(stp, super);
  		if (min_size == 0)
  			continue;
  		for (i = 0; i<  stp->total; i++)

diff --git a/mdadm.h b/mdadm.h
index 4ef3ee5..7047fdf 100644
--- a/mdadm.h
+++ b/mdadm.h

@@ -605,6 +605,7 @@ extern struct superswitch {
  	int (*load_super)(struct supertype *st, int fd, char *devname);
  	struct supertype * (*match_metadata_desc)(char *arg);
  	__u64 (*avail_size)(struct supertype *st, __u64 size);
+	unsigned long long (*min_acceptable_spare_size)(struct supertype

*st);

quoted

  	int (*add_internal_bitmap)(struct supertype *st, int *chunkp,
  				   int delay, int write_behind,
  				   unsigned long long size, int may_change, int

major);

quoted

diff --git a/super-intel.c b/super-intel.c
index bcc202e..77c9d7f 100644
--- a/super-intel.c
+++ b/super-intel.c

@@ -646,6 +646,37 @@ static int is_failed(struct imsm_disk *disk)
  	return (disk->status&  FAILED_DISK) == FAILED_DISK;
  }

+/* Return minimum size of a spare that can be used in this array*/
+static unsigned long long min_acceptable_spare_size_imsm(struct

supertype *st)

quoted

+{
+	struct intel_super *super = st->sb;
+	struct dl *dl;
+	struct extent *e;
+	int i;
+	unsigned long long rv = 0;
+
+	if (!super)
+		return rv;
+	/* find first active disk in array */
+	dl = super->disks;
+	while (dl&&  (is_failed(&dl->disk) || dl->index == -1))
+		dl = dl->next;
+	if (!dl)
+		return rv;
+	/* find last lba used by subarrays */
+	e = get_extents(super, dl);
+	if (!e)
+		return rv;
+	for (i = 0; e[i].size; i++)
+		continue;
+	if (i>  0)
+		rv = e[i-1].start + e[i-1].size;
+	free(e);
+	/* add the amount of space needed for metadata */
+	rv = rv + MPB_SECTOR_CNT + IMSM_RESERVED_SECTORS;
+	return rv * 512;
+}
+
  #ifndef MDASSEMBLE
  static __u64 blocks_per_migr_unit(struct imsm_dev *dev);

@@ -5629,6 +5660,7 @@ struct superswitch super_imsm = {
  	.update_super	= update_super_imsm,

  	.avail_size	= avail_size_imsm,
+	.min_acceptable_spare_size = min_acceptable_spare_size_imsm,

Neil wondered if we can repurpose validate_geometry for this case?  It
is already charged with checking if a disk is suitable to be added to
an
array.

I had a look at validate_geometry and I don't think it makes sense to modify it for Monitor.
Validate_geometry is made for Create. When creating container validate_geometry doesn't check much for imsm. When adding to a volume all disks must be already in the same container and have some common free region. We want the check before we move a spare. And the whole spare is free (is not used by any arrays in that container). I think it is better to have smaller functions and use them as building blocks, than make a big function even more complicated for every special case.
Regards
Anna
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