linux-toradex.git/drivers/md/bitmap.h, branch v3.12-rc7

md/bitmap: record the space available for the bitmap in the superblock.

2012-05-22T03:55:34+00:00

Now that bitmaps can grow and shrink it is best if we record
how much space is available.  This means that when
we reduce the size of the bitmap we won't "lose" the space
for late when we might want to increase the size of the bitmap
again.

Signed-off-by: NeilBrown

md/bitmap: add bitmap_resize function to allow bitmap resizing.

2012-05-22T03:55:25+00:00

This function will allocate the new data structures and copy
bits across from old to new, allowing for the possibility that the
chunksize has changed.

Use the same function for performing the initial allocation
of the structures.  This improves test coverage.

When bitmap_resize is used to resize an existing bitmap, it
only copies '1' bits in, not '0' bits.
So when allocating the bitmap, ensure everything is initialised
to ZERO.

Signed-off-by: NeilBrown

md/bitmap: create a 'struct bitmap_counts' substructure of 'struct bitmap'

2012-05-22T03:55:24+00:00

The new "struct bitmap_counts" contains all the fields that are
related to counting the number of active writes in each bitmap chunk.

Having this separate will make it easier to change the chunksize
or overall size of a bitmap atomically.

Signed-off-by: NeilBrown

md/bitmap: use set_bit, test_bit, etc for operation on bitmap->flags.

2012-05-22T03:55:15+00:00

We currently use '&' and '|' which isn't the norm in the kernel
and doesn't allow easy atomicity.
So change to bit numbers and {set,clear,test}_bit.
This allows us to remove a spinlock/unlock (which was dubious anyway)
and some other simplifications.

Signed-off-by: NeilBrown

md/bitmap: store bytes in file rather than just in last page.

2012-05-22T03:55:11+00:00

This number is more generally useful, and bytes-in-last-page is
easily extracted from it.

Signed-off-by: NeilBrown

md/bitmap: move some fields of 'struct bitmap' into a 'storage' substruct.

2012-05-22T03:55:10+00:00

This new 'struct bitmap_storage' reflects the external storage of the
bitmap.
Having this clearly defined will make it easier to change the storage
used while the array is active.

Signed-off-by: NeilBrown

md/bitmap: disentangle two different 'pending' flags.

2012-05-22T03:55:06+00:00

There are two different 'pending' concepts in the handling of the
write intent bitmap.

Firstly, a 'page' from the bitmap (which container PAGE_SIZE*8 bits)
may have changes (bits cleared) that should be written in due course.
There is no hurry for these and the page will transition from
PENDING to NEEDWRITE and will then be written, though if it ever
becomes DIRTY it will be written much sooner and PENDING will be
cleared.

Secondly, a page of counters - which contains PAGE_SIZE/2 counters, one
for each bit, can usefully have a 'pending' flag which indicates if
any of the counters are low (2 or 1) and ready to be processed by
bitmap_daemon_work().  If this flag is clear we can skip the whole
page.

These two concepts are currently combined in the bitmap-file flag.
This causes a tighter connection between the counters and the bitmap
file than I would like - as I want to add some flexibility to the
bitmap file.

So introduce a new flag with the page-of-counters, and rewrite
bitmap_daemon_work() so that it handles the two different 'pending'
concepts separately.

This also allows us to clear BITMAP_PAGE_PENDING when we write out
a dirty page, which may occasionally reduce the number of times we
write a page.

Signed-off-by: NeilBrown

md/bitmap: fix calculation of 'chunks' - missing shift.

2012-05-04T07:03:18+00:00

commit 61a0d80c "md/bitmap: discard CHUNK_BLOCK_SHIFT macro"
replaced CHUNK_BLOCK_RATIO() by the same text that was
replacing CHUNK_BLOCK_SHIFT() - which is clearly wrong.

The result is that 'chunks' is often too small by 1,
which can sometimes result in a crash (not sure how).

So use the correct replacement, and get rid of CHUNK_BLOCK_RATIO
which is no longe used.

Reported-by: Karl Newman 
Tested-by: Karl Newman 
Signed-off-by: NeilBrown

md/bitmap: discard CHUNK_BLOCK_SHIFT macro

2012-03-19T01:46:41+00:00

Be redefining ->chunkshift as the shift from sectors to chunks rather
than bytes to chunks, we can just use "bitmap->chunkshift" which is
shorter than the macro call, and less indirect.

Signed-off-by: NeilBrown

md/bitmap: move printing of bitmap status to bitmap.c

2012-03-19T01:46:40+00:00

The part of /proc/mdstat which describes the bitmap should really
be generated by code in bitmap.c.  So move it there.

Signed-off-by: NeilBrown