Eric Lee / linux-smarc-t335x-v3.2

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Commit df8e7f7639bab3b2cc536a1d30d5593d65251778

Authored by NeilBrown
Committed by Linus Torvalds
1 parent e464eafdb4
Exists in master and in 4 other branches v3.2_AM335xPSP_04.06.00.11, v3.2_NEWT335xPSP_04.06.00.11, v3.2_SBC_SMARTMEN, v3.2_SMARCT335xPSP_04.06.00.11

[PATCH] md: Improve comments about locking situation in raid5 make_request 

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

Showing 1 changed file with 14 additions and 1 deletions Side-by-side Diff

... ... @@ -1768,6 +1768,14 @@
1768 1768 if (likely(conf->expand_progress == MaxSector))
1769 1769 disks = conf->raid_disks;
1770 1770 else {
  1771 + /* spinlock is needed as expand_progress may be
  1772 + * 64bit on a 32bit platform, and so it might be
  1773 + * possible to see a half-updated value
  1774 + * Ofcourse expand_progress could change after
  1775 + * the lock is dropped, so once we get a reference
  1776 + * to the stripe that we think it is, we will have
  1777 + * to check again.
  1778 + */
1771 1779 spin_lock_irq(&conf->device_lock);
1772 1780 disks = conf->raid_disks;
1773 1781 if (logical_sector >= conf->expand_progress)
... ... @@ -1791,7 +1799,12 @@
1791 1799 if (sh) {
1792 1800 if (unlikely(conf->expand_progress != MaxSector)) {
1793 1801 /* expansion might have moved on while waiting for a
1794   - * stripe, so we much do the range check again.
  1802 + * stripe, so we must do the range check again.
  1803 + * Expansion could still move past after this
  1804 + * test, but as we are holding a reference to
  1805 + * 'sh', we know that if that happens,
  1806 + * STRIPE_EXPANDING will get set and the expansion
  1807 + * won't proceed until we finish with the stripe.
1795 1808 */
1796 1809 int must_retry = 0;
1797 1810 spin_lock_irq(&conf->device_lock);