block: blk-merge: don't merge the pages with non-contiguous descriptors

blk_rq_map_sg() function merges the physically contiguous pages to use same
scatter-gather node without checking if their page descriptors are
contiguous or not.

Now when dma_map_sg() is called on the scatter gather list, it would
take the base page pointer from each node (one by one) and iterates
through all of the pages in same sg node by keep incrementing the base
page pointer with the assumption that physically contiguous pages will
have their page descriptor address contiguous which may not be true
if SPARSEMEM config is enabled. So here we may end referring to invalid
page descriptor.

Following table shows the example of physically contiguous pages but
their page descriptor addresses non-contiguous.
-------------------------------------------
| Page Descriptor    |   Physical Address |
------------------------------------------
| 0xc1e43fdc         |   0xdffff000       |
| 0xc2052000         |   0xe0000000       |
-------------------------------------------

With this patch, relevant blk-merge functions will also check if the
physically contiguous pages are having page descriptors address contiguous
or not? If not then, these pages are separated to be in different
scatter-gather nodes.

Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: nicholas <firepoison35@gmail.com>
block: Add API for urgent request handling

This patch add support in block & elevator layers for handling
urgent requests. The decision if a request is urgent or not is taken
by the scheduler. Urgent request notification is passed to the underlying
block device driver (eMMC for example). Block device driver may decide to
interrupt the currently running low priority request to serve the new
urgent request. By doing so READ latency is greatly reduced in read&write
collision scenarios.

Note that if the current scheduler doesn't implement the urgent request
mechanism, this code path is never activated.

Change-Id: I8aa74b9b45c0d3a2221bd4e82ea76eb4103e7cfa
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>

Conflicts:
	include/linux/elevator.h
block: Reserve only one queue tag for sync IO if only 3 tags are available

In case a device has three tags available we still reserve two of them
for sync IO. That leaves only a single tag for async IO such as
writeback from flusher thread which results in poor performance.

Allow async IO to consume two tags in case queue has three tag availabe
to get a decent async write performance.

This patch improves streaming write performance on a machine with such disk
from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of
streaming writer improves from 8 to 12 transactions per second so sync
IO doesn't seem to be harmed in presence of heavy async writer.
block,elevator: use new hashtable implementation

Switch elevator to use the new hashtable implementation. This reduces the
amount of generic unrelated code in the elevator.

This also removes the dymanic allocation of the hash table. The size of the table is
constant so there's no point in paying the price of an extra dereference when accessing
it.

This patch depends on d9b482c ("hashtable: introduce a small and naive
hashtable") which was merged in v3.6.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
block: blk-map: re-use existing 'reading' variable instead of checking direction
block: make register_disk() static
Revert "block,elevator: use new hashtable implementation"

This reverts commit 5405e485c437a1b155231fab43124fb7522532d5.
Revert "block: Add API for urgent request handling"

This reverts commit f662f3803b3e785affdfdd88cfde8e41b57a3da0.
block: Add support for reinsert a dispatched req

Add support for reinserting a dispatched request back to the
scheduler's internal data structures.
This capability is used by the device driver when it chooses to
interrupt the current request transmission and execute another (more
urgent) pending request. For example: interrupting long write in order
to handle pending read. The device driver re-inserts the
remaining write request back to the scheduler, to be rescheduled
for transmission later on.

Add API for verifying whether the current scheduler
supports reinserting requests mechanism. If reinsert mechanism isn't
supported by the scheduler, this code path will never be activated.
block: Add API for urgent request handling

This patch add support in block & elevator layers for handling
urgent requests. The decision if a request is urgent or not is taken
by the scheduler. Urgent request notification is passed to the underlying
block device driver (eMMC for example). Block device driver may decide to
interrupt the currently running low priority request to serve the new
urgent request. By doing so READ latency is greatly reduced in read&write
collision scenarios.

Note that if the current scheduler doesn't implement the urgent request
mechanism, this code path is never activated.

Change-Id: I8aa74b9b45c0d3a2221bd4e82ea76eb4103e7cfa
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>

Conflicts:
	include/linux/elevator.h
block: fix backport of row patches

Change-Id: I5898bfaf153144a370d0f8517e43bf68b03ae605
Revert "block: Add support for reinsert a dispatched req"

This reverts commit f86855dea2e798a33d6809c90b5c5f219d55c77c.
Revert "block: fix backport of row patches"

This reverts commit e5a178db2fb422500fa3021012aa9fd522fbeaaf.
Revert "block: Add API for urgent request handling"

This reverts commit 043b4803e642926c3772039269012d351be171c4.
fs/proc/base.c (affects lowmemorykiller): oom_adj -17 triggers oom_score_adj of -1000

Prior to this patch, oom_score_adj was automatically calculated based
on the oom_adj value.
When setting an oom_adj value of the minium value (-17), automatically
set oom_score_adj to its minimum value (-1000) as well.
Added fsync control

Conflicts:
	drivers/misc/Kconfig
	drivers/misc/Makefile
sync.c: add a module_param to fsync() calls. fsync is still disabled by default but users will have the choice of having a faster build or a safer build (for data integrity). Props for simms for busting my ass off with this one :)
Added DYNAMIC FSYNC CONTROL
dynamic fsync: Enable sync globally
Enable dyn_fsync at boot