linux.git/drivers/md/linear.c, branch v2.6.29

md: Fix a bug in linear.c causing which_dev() to return the wrong device.

2009-02-06T04:10:52+00:00

ab5bd5cbc8d4b868378d062eed3d4240930fbb86 introduced the following
bug in linear software raid for large arrays on 32 bit machines:

which_dev() computes the device holding a given sector by shifting
down the sector number to a 32 bit range, dividing by the array
spacing and looking up the resulting index in the hash table of
the array.

Because the computed index might be slightly too small, a loop at
the end of which_dev() increases the index until the given sector
actually falls into the range of the device associated with that index.

The changes of the above mentioned commit caused this loop to check
whether the _index_ rather than the sector number is small enough,
effectively bypassing the loop and thus possibly returning the wrong
device.

As reported by Simon Kirby, this leads to errors such as

	linear_make_request: Sector 2340486136 out of bounds on dev sdi: 156301312 sectors, offset 2109870464

Fix this bug by introducing a local variable for the index so that
the variable containing the passed sector is left unchanged.

Cc: stable@kernel.org
Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: use list_for_each_entry macro directly

2009-01-08T21:31:08+00:00

The rdev_for_each macro defined in  is identical to
list_for_each_entry_safe, from , it should be defined to
use list_for_each_entry_safe, instead of reinventing the wheel.

But some calls to each_entry_safe don't really need a safe version,
just a direct list_for_each_entry is enough, this could save a temp
variable (tmp) in every function that used rdev_for_each.

In this patch, most rdev_for_each loops are replaced by list_for_each_entry,
totally save many tmp vars; and only in the other situations that will call
list_del to delete an entry, the safe version is used.

Signed-off-by: Cheng Renquan 
Signed-off-by: NeilBrown

md: linear: Fix a division by zero bug for very small arrays.

2008-11-06T08:41:24+00:00

We currently oops with a divide error on starting a linear software
raid array consisting of at least two very small (< 500K) devices.

The bug is caused by the calculation of the hash table size which
tries to compute sector_div(sz, base) with "base" being zero due to
the small size of the component devices of the array.

Fix this by requiring the hash spacing to be at least one which
implies that also "base" is non-zero.

This bug has existed since about 2.6.14.

Cc: stable@kernel.org
Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: Remove unnecessary #includes, #defines, and function declarations.

2008-10-13T00:55:12+00:00

A lot of cruft has gathered over the years.  Time to remove it.

Signed-off-by: NeilBrown

md: Convert remaining 1k representations in linear.c to sectors.

2008-10-13T00:55:12+00:00

This patch renames hash_spacing and preshift to  spacing and
sector_shift respectively with the following change of semantics:

Case 1: (sizeof(sector_t) <= sizeof(u32)).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

In this case, we have sector_shift = preshift = 0 and spacing =
2 * hash_spacing.

Hence, the index for the hash table which is computed by the new code
in which_dev() as sector / spacing equals the old value which was
(sector/2) / hash_spacing.

Note also that the value of nb_zone stays the same because both sz
and base double.

Case 2: (sizeof(sector_t) > sizeof(u32)).
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

(aka the shifting dance case). Here we have sector_shift = preshift +
1 and

spacing = 2 * hash_spacing

during the computation of nb_zone and curr_sector, but

spacing = hash_spacing

in which_dev() because in the last hunk of the patch for linear.c we
shift down conf->spacing (= 2 * hash_spacing) by one more bit than
in the old code.

Hence in the computation of nb_zone, sz and base have the same value
as before, so nb_zone is not affected. Also curr_sector in the next
hunk stays the same.

In which_dev() the hash table index is computed as

(sector >> sector_shift) / spacing

In view of sector_shift = preshift + 1 and spacing = hash_spacing,
this equals

((sector/2) >> preshift) / hash_spacing

which is the value computed by the old code.

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: linear.c: Make two local variables sector-based.

2008-10-13T00:55:12+00:00

This is a preparation for representing also the remaining fields of struct
linear_private_data as sectors.

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: linear: Represent dev_info->size and dev_info->offset in sectors.

2008-10-13T00:55:12+00:00

Rename them to num_sectors and start_sector which is more descriptive.

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: linear.c: Remove broken debug code.

2008-10-13T00:55:12+00:00

conf->smallest_size is undefined since day one of the git repo..

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: linear.c: Remove pointless initialization of curr_offset.

2008-10-13T00:55:12+00:00

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown

md: linear.c: Fix typo in comment.

2008-10-13T00:55:12+00:00

Signed-off-by: Andre Noll 
Signed-off-by: NeilBrown