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  1. 04 Aug, 2009 3 commits
    • Linus Torvalds's avatar
      tty-ldisc: be more careful in 'put_ldisc' locking · cbe9352f
      Linus Torvalds authored 
      Use 'atomic_dec_and_lock()' to make sure that we always hold the
tty_ldisc_lock when the ldisc count goes to zero. That way we can never
race against 'tty_ldisc_try()' increasing the count again.
Reported-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@mail.by>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      cbe9352f
    • Linus Torvalds's avatar
      tty-ldisc: turn ldisc user count into a proper refcount · 65b77046
      Linus Torvalds authored 
      By using the user count for the actual lifetime rules, we can get rid of
the silly "wait_for_idle" logic, because any busy ldisc will
automatically stay around until the last user releases it.  This avoids
a host of odd issues, and simplifies the code.

So now, when the last ldisc reference is dropped, we just release the
ldisc operations struct reference, and free the ldisc.

It looks obvious enough, and it does work for me, but the counting
_could_ be off. It probably isn't (bad counting in the new version would
generally imply that the old code did something really bad, like free an
ldisc with a non-zero count), but it does need some testing, and
preferably somebody looking at it.

With this change, both 'tty_ldisc_put()' and 'tty_ldisc_deref()' are
just aliases for the new ref-counting 'put_ldisc()'. Both of them
decrement the ldisc user count and free it if it goes down to zero.
They're identical functions, in other words.

But the reason they still exist as sepate functions is that one of them
was exported (tty_ldisc_deref) and had a stupid name (so I don't want to
use it as the main name), and the other one was used in multiple places
(and I didn't want to make the patch larger just to rename the users).

In addition to the refcounting, I did do some minimal cleanup. For
example, now "tty_ldisc_try()" actually returns the ldisc it got under
the lock, rather than returning true/false and then the caller would
look up the ldisc again (now without the protection of the lock).

That said, there's tons of dubious use of 'tty->ldisc' without obviously
proper locking or refcounting left. I expressly did _not_ want to try to
fix it all, keeping the patch minimal. There may or may not be bugs in
that kind of code, but they wouldn't be _new_ bugs.

That said, even if the bugs aren't new, the timing and lifetime will
change. For example, some silly code may depend on the 'tty->ldisc'
pointer not changing because they hold a refcount on the 'ldisc'. And
that's no longer true - if you hold a ref on the ldisc, the 'ldisc'
itself is safe, but tty->ldisc may change.

So the proper locking (remains) to hold tty->ldisc_mutex if you expect
tty->ldisc to be stable. That's not really a _new_ rule, but it's an
example of something that the old code might have unintentionally
depended on and hidden bugs.

Whatever. The patch _looks_ sensible to me. The only users of
ldisc->users are:
 - get_ldisc() - atomically increment the count

 - put_ldisc() - atomically decrements the count and releases if zero

 - tty_ldisc_try_get() - creates the ldisc, and sets the count to 1.
   The ldisc should then either be released, or be attached to a tty.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@mail.by>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      65b77046
    • Linus Torvalds's avatar
      tty-ldisc: make refcount be atomic_t 'users' count · 18eac1cc
      Linus Torvalds authored 
      This is pure preparation of changing the ldisc reference counting to be
a true refcount that defines the lifetime of the ldisc.  But this is a
purely syntactic change for now to make the next steps easier.

This patch should make no semantic changes at all. But I wanted to make
the ldisc refcount be an atomic (I will be touching it without locks
soon enough), and I wanted to rename it so that there isn't quite as
much confusion between 'ldo->refcount' (ldisk operations refcount) and
'ld->refcount' (ldisc refcount itself) in the same file.

So it's now an atomic 'ld->users' count. It still starts at zero,
despite having a reference from 'tty->ldisc', but that will change once
we turn it into a _real_ refcount.
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
Tested-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Tested-by: default avatarSergey Senozhatsky <sergey.senozhatsky@mail.by>
Acked-by: default avatarAlan Cox <alan@linux.intel.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
      18eac1cc
  3. 03 Aug, 2009 8 commits
    • Linus Torvalds's avatar
      Merge branch 'for-linus' of git://neil.brown.name/md · a33a052f
      Linus Torvalds authored 
      * 'for-linus' of git://neil.brown.name/md:
  md: Use revalidate_disk to effect changes in size of device.
  md: allow raid5_quiesce to work properly when reshape is happening.
  md/raid5: set reshape_position correctly when reshape starts.
  md: Handle growth of v1.x metadata correctly.
  md: avoid array overflow with bad v1.x metadata
  md: when a level change reduces the number of devices, remove the excess.
  md: Push down data integrity code to personalities.
  md/raid6: release spare page at ->stop()
      a33a052f
    • NeilBrown's avatar
      md: Use revalidate_disk to effect changes in size of device. · 449aad3e
      NeilBrown authored 
      As revalidate_disk calls check_disk_size_change, it will cause
any capacity change of a gendisk to be propagated to the blockdev
inode.  So use that instead of mucking about with locks and
i_size_write.

Also add a call to revalidate_disk in do_md_run and a few other places
where the gendisk capacity is changed.
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      449aad3e
    • NeilBrown's avatar
      md: allow raid5_quiesce to work properly when reshape is happening. · 64bd660b
      NeilBrown authored 
      The ->quiesce method is not supposed to stop resync/recovery/reshape,
just normal IO.
But in raid5 we don't have a way to know which stripes are being
used for normal IO and which for resync etc, so we need to wait for
all stripes to be idle to be sure that all writes have completed.

However reshape keeps at least some stripe busy for an extended period
of time, so a call to raid5_quiesce can block for several seconds
needlessly.
So arrange for reshape etc to pause briefly while raid5_quiesce is
trying to quiesce the array so that the active_stripes count can
drop to zero.
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      64bd660b
    • NeilBrown's avatar
      md/raid5: set reshape_position correctly when reshape starts. · e516402c
      NeilBrown authored 
      As the internal reshape_progress counter is the main driver
for reshape, the fact that reshape_position sometimes starts with the
wrong value has minimal effect.  It is visible in sysfs and that
is all.
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      e516402c
    • NeilBrown's avatar
      md: Handle growth of v1.x metadata correctly. · 70471daf
      NeilBrown authored 
      The v1.x metadata does not have a fixed size and can grow
when devices are added.
If it grows enough to require an extra sector of storage,
we need to update the 'sb_size' to match.

Without this, md can write out an incomplete superblock with a
bad checksum, which will be rejected when trying to re-assemble
the array.

Cc: stable@kernel.org
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      70471daf
    • NeilBrown's avatar
      md: avoid array overflow with bad v1.x metadata · 3673f305
      NeilBrown authored 
      We trust the 'desc_nr' field in v1.x metadata enough to use it
as an index in an array.  This isn't really safe.
So range-check the value first.
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      3673f305
    • NeilBrown's avatar
      md: when a level change reduces the number of devices, remove the excess. · 3a981b03
      NeilBrown authored 
      When an array is changed from RAID6 to RAID5, fewer drives are
needed.  So any device that is made superfluous by the level
conversion must be marked as not-active.
For the RAID6->RAID5 conversion, this will be a drive which only
has 'Q' blocks on it.

Cc: stable@kernel.org
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      3a981b03
    • Andre Noll's avatar
      md: Push down data integrity code to personalities. · ac5e7113
      Andre Noll authored 
      This patch replaces md_integrity_check() by two new public functions:
md_integrity_register() and md_integrity_add_rdev() which are both
personality-independent.

md_integrity_register() is called from the ->run and ->hot_remove
methods of all personalities that support data integrity.  The
function iterates over the component devices of the array and
determines if all active devices are integrity capable and if their
profiles match. If this is the case, the common profile is registered
for the mddev via blk_integrity_register().

The second new function, md_integrity_add_rdev() is called from the
->hot_add_disk methods, i.e. whenever a new device is being added
to a raid array. If the new device does not support data integrity,
or has a profile different from the one already registered, data
integrity for the mddev is disabled.

For raid0 and linear, only the call to md_integrity_register() from
the ->run method is necessary.
Signed-off-by: default avatarAndre Noll <maan@systemlinux.org>
Signed-off-by: default avatarNeilBrown <neilb@suse.de>
      ac5e7113
  5. 02 Aug, 2009 21 commits
  7. 01 Aug, 2009 3 commits
  9. 31 Jul, 2009 5 commits
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