pcluster should be only set up for all managed pages instead of
temporary pages. Since it currently uses page->mapping to identify,
the impact is minor for now.

[ Update: Vladimir reported the kernel log becomes polluted
  because PAGE_FLAGS_CHECK_AT_FREE flag(s) set if the page
  allocation debug option is enabled. ]

Link: https://lore.kernel.org/r/20201022145724.27284-1-hsiangkao@aol.com
Fixes: 5ddcee1f ("erofs: get rid of __stagingpage_alloc helper")
Cc: <stable@vger.kernel.org> # 5.5+
Tested-by: NVladimir Zapolskiy <vladimir@tuxera.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>

Let's add REQ_RAHEAD flag so it'd be easier to identify
readahead I/O requests in blktrace.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200919072730.24989-3-hsiangkao@redhat.comSigned-off-by: NGao Xiang <hsiangkao@redhat.com>

should_decompress_synchronously() has one single condition
for now, so fold it instead.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200919072730.24989-2-hsiangkao@redhat.comSigned-off-by: NGao Xiang <hsiangkao@redhat.com>

variable `err' in z_erofs_submit_queue() isn't useful
here, remove it instead.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200919072730.24989-1-hsiangkao@redhat.comSigned-off-by: NGao Xiang <hsiangkao@redhat.com>

After commit 0615090c ("erofs: convert compressed files from
readpages to readahead"), add_to_page_cache_lru() was moved to mm
code, so that in below call path, no page will be cached into
@pagepool list or grabbed from @pagepool list:
- z_erofs_readpage
 - z_erofs_do_read_page
  - preload_compressed_pages
  - erofs_allocpage

Let's get rid of this unneeded @pagepool parameter.
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200917011821.22767-1-yuchao0@huawei.comReviewed-by: NGao Xiang <hsiangkao@redhat.com>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>

The documentation [1] says that WQ_CPU_INTENSIVE is "meaningless" for
unbound wq. I remove this flag from places where unbound queue is
allocated. This is supposed to improve code readability.

[1] https://www.kernel.org/doc/html/latest/core-api/workqueue.html#flagsSigned-off-by: NMaksym Planeta <mplaneta@os.inf.tu-dresden.de>
[Gao Xiang: since the original treewide patch [2] hasn't been merged
            yet, handling the EROFS part only for the next cycle. ]
[2] https://lore.kernel.org/r/20200213141823.2174236-1-mplaneta@os.inf.tu-dresden.de
Link: https://lore.kernel.org/r/20200731024049.16495-1-hsiangkao@aol.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <hsiangkao@redhat.com>

Rationale:
Reduces attack surface on kernel devs opening the links for MITM
as HTTPS traffic is much harder to manipulate.

Deterministic algorithm:
For each file:
  If not .svg:
    For each line:
      If doesn't contain `\bxmlns\b`:
        For each link, `\bhttp://[^# \t\r\n]*(?:\w|/)`:
	  If neither `\bgnu\.org/license`, nor `\bmozilla\.org/MPL\b`:
            If both the HTTP and HTTPS versions
            return 200 OK and serve the same content:
              Replace HTTP with HTTPS.
Reviewed-by: NGao Xiang <hsiangkao@redhat.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NAlexander A. Klimov <grandmaster@al2klimov.de>
Link: https://lore.kernel.org/r/20200713130944.34419-1-grandmaster@al2klimov.deSigned-off-by: NGao Xiang <hsiangkao@redhat.com>

Using uninitialized_var() is dangerous as it papers over real bugs[1]
(or can in the future), and suppresses unrelated compiler warnings
(e.g. "unused variable"). If the compiler thinks it is uninitialized,
either simply initialize the variable or make compiler changes.

In preparation for removing[2] the[3] macro[4], remove all remaining
needless uses with the following script:

git grep '\buninitialized_var\b' | cut -d: -f1 | sort -u | \
	xargs perl -pi -e \
		's/\buninitialized_var\(([^\)]+)\)/\1/g;
		 s:\s*/\* (GCC be quiet|to make compiler happy) \*/$::g;'

drivers/video/fbdev/riva/riva_hw.c was manually tweaked to avoid
pathological white-space.

No outstanding warnings were found building allmodconfig with GCC 9.3.0
for x86_64, i386, arm64, arm, powerpc, powerpc64le, s390x, mips, sparc64,
alpha, and m68k.

[1] https://lore.kernel.org/lkml/20200603174714.192027-1-glider@google.com/
[2] https://lore.kernel.org/lkml/CA+55aFw+Vbj0i=1TGqCR5vQkCzWJ0QxK6CernOU6eedsudAixw@mail.gmail.com/
[3] https://lore.kernel.org/lkml/CA+55aFwgbgqhbp1fkxvRKEpzyR5J8n1vKT1VZdz9knmPuXhOeg@mail.gmail.com/
[4] https://lore.kernel.org/lkml/CA+55aFz2500WfbKXAx8s67wrm9=yVJu65TpLgN_ybYNv0VEOKA@mail.gmail.com/

Reviewed-by: Leon Romanovsky <leonro@mellanox.com> # drivers/infiniband and mlx4/mlx5
Acked-by: Jason Gunthorpe <jgg@mellanox.com> # IB
Acked-by: Kalle Valo <kvalo@codeaurora.org> # wireless drivers
Reviewed-by: Chao Yu <yuchao0@huawei.com> # erofs
Signed-off-by: NKees Cook <keescook@chromium.org>

Use the new readahead operation in erofs.
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NDave Chinner <dchinner@redhat.com>
Reviewed-by: NWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Acked-by: NGao Xiang <gaoxiang25@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-20-willy@infradead.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Use the new readahead operation in erofs
Signed-off-by: NMatthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Reviewed-by: NWilliam Kucharski <william.kucharski@oracle.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Acked-by: NGao Xiang <gaoxiang25@huawei.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Cong Wang <xiyou.wangcong@gmail.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Joseph Qi <joseph.qi@linux.alibaba.com>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc: Miklos Szeredi <mszeredi@redhat.com>
Link: http://lkml.kernel.org/r/20200414150233.24495-19-willy@infradead.orgSigned-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Convert the erofs to use new internal mount API as the old one will
be obsoleted and removed.  This allows greater flexibility in
communication of mount parameters between userspace, the VFS and the
filesystem.

See Documentation/filesystems/mount_api.txt for more information.

Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20200529104836.17843-1-hsiangkao@redhat.comSigned-off-by: NGao Xiang <hsiangkao@redhat.com>

XArray has friendly APIs and it will replace the old radix
tree in the near future.

This convert makes use of __xa_cmpxchg when inserting on
a just inserted item by other thread. In detail, instead
of totally looking up again as what we did for the old
radix tree, it will try to legitimize the current in-tree
item in the XArray therefore more effective.

In addition, naming is rather a challenge for non-English
speaker like me. The basic idea of workstn is to provide
a runtime sparse array with items arranged in the physical
block number order. Such items (was called workgroup) can be
used to record compress clusters or for later new features.

However, both workgroup and workstn seem not good names from
whatever point of view, so I'd like to rename them as pslot
and managed_pslots to stand for physical slots. This patch
handles the second as a part of the radix tree convert.

Cc: Matthew Wilcox <willy@infradead.org>
Link: https://lore.kernel.org/r/20200220024642.91529-1-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

A label and extra variables will be eliminated,
which is more cleaner.

Link: https://lore.kernel.org/r/20200121064819.139469-1-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

No need to introduce such separated helper since
cache strategy compile configs were changed into
runtime options instead in v5.4. No logic changes.

Link: https://lore.kernel.org/r/20200121064747.138987-1-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

All workgroups are registered with tag value set to 0, to simplify
erofs_register_workgroup() interface the tag argument can be removed,
if its only value is sent down to the function body.
Signed-off-by: NVladimir Zapolskiy <vladimir@tuxera.com>
Link: https://lore.kernel.org/r/20200102120118.14979-3-vladimir@tuxera.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

It is feasible to simplify erofs_find_workgroup() interface by removing
an unused function argument. While formally the argument is used in the
function itself, its assigned value is ignored on the caller side.
Signed-off-by: NVladimir Zapolskiy <vladimir@tuxera.com>
Link: https://lore.kernel.org/r/20200102120118.14979-2-vladimir@tuxera.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

VLE was an old informal name of fixed-sized output
compression which came from published ATC'19 paper [1].

Drop those old annotations since erofs can handle
all encoded clusters in block-aligned basis, which
is wider than fixed-sized output compression after
larger clustersize feature is fully implemented.

Unaligned encoding won't be considered in EROFS
since it's not friendly to inplace I/O and perhaps
decompression inplace.

a) Fixed-sized output compression with 16KB pcluster:
  ___________________________________
 |xxxxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|
 |___ 0___|___ 1___|___ 2___|___ 3___| physical blocks

b) Block-aligned fixed-sized input compression with
   16KB pcluster:
  ___________________________________
 |xxxxxxxx|xxxxxxxx|xxxxxxxx|xxx00000|
 |___ 0___|___ 1___|___ 2___|___ 3___| physical blocks

c) Block-unaligned fixed-sized input compression with
   16KB compression unit:
  ____________________________________________
 |..xxxxxx|xxxxxxxx|xxxxxxxx|xxxxxxxx|x.......|
 |___ 0___|___ 1___|___ 2___|___ 3___|___ 4___| physical blocks

Refine better names for those as well.

[1] https://www.usenix.org/conference/atc19/presentation/gao

Link: https://lore.kernel.org/r/20191108033733.63919-1-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

For those tasks waiting I/O for sync decompression,
they should be better marked as IO wait state.

Link: https://lore.kernel.org/r/20191008125616.183715-5-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

Previously, both z_erofs_unzip_io and z_erofs_unzip_io_sb
record decompress queues for backend to use.

The only difference is that z_erofs_unzip_io is used for
on-stack sync decompression so that it doesn't have a super
block field (since the caller can pass it in its context),
but it increases complexity with only a pointer saving.

Rename z_erofs_unzip_io to z_erofs_decompressqueue with
a fixed super_block member and kill the other entirely,
and it can fallback to sync decompression if memory
allocation failure.

Link: https://lore.kernel.org/r/20191008125616.183715-4-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

Now open code is much cleaner due to iterative development.

Link: https://lore.kernel.org/r/20191124025217.12345-1-hsiangkao@aol.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

After commit 4279f3f9 ("staging: erofs: turn cache
strategies into mount options"), cache strategies are
changed into mount options rather than old build configs.

Let's kill useless code for obsoleted build options.

Link: https://lore.kernel.org/r/20191008125616.183715-2-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

 - change return value to int since collection is
   already returned within the collector.
 - better function naming.

Link: https://lore.kernel.org/r/20191008125616.183715-1-gaoxiang25@huawei.comReviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>

Fix a recent cleanup patch. noio (bypass) chain is
handled asynchronously against submit chain, therefore
inplace I/O or pagevec cannot be applied to such pages.
Add detailed comment for this as well.

Fixes: 97e86a85 ("staging: erofs: tidy up decompression frontend")
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190922100434.229340-1-gaoxiang25@huawei.comSigned-off-by: NGao Xiang <gaoxiang25@huawei.com>

Add prefix "erofs_" to these functions and print
sb->s_id as a prefix to erofs_{err, info} so that
the user knows which file system is affected.
Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-23-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As Christoph suggested [1], "Please just use plain kmalloc
everywhere and let the normal kernel error injection code
take care of injeting any errors."

[1] https://lore.kernel.org/r/20190829102426.GE20598@infradead.org/Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-20-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Add erofs_ prefix to free_inode, alloc_inode, ...
Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-19-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As Christoph pointed out [1], "
Why is there __submit_bio which really just obsfucates
what is going on?  Also why is __submit_bio using
bio_set_op_attrs instead of opencode it as the comment
right next to it asks you to? "

Let's use submit_bio directly instead.

[1] https://lore.kernel.org/r/20190830162812.GA10694@infradead.org/Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-18-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As Christoph pointed out [1], "erofs_grab_bio tries to
handle a bio_alloc failure, except that the function will
not actually fail due the mempool backing it."

Sorry about useless code, fix it now and
localize erofs_grab_bio [2].

[1] https://lore.kernel.org/r/20190830162812.GA10694@infradead.org/
[2] https://lore.kernel.org/r/20190902122016.GL15931@infradead.org/Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-16-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As Christoph suggested [1], "Why is this called vnode instead
of inode?  That seems like a rather odd naming for a Linux
file system."

[1] https://lore.kernel.org/r/20190829101545.GC20598@infradead.org/Reported-by: NChristoph Hellwig <hch@infradead.org>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190904020912.63925-10-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As Dan Carpenter suggested [1], I have to remove
all erofs likely/unlikely annotations.

[1] https://lore.kernel.org/linux-fsdevel/20190829154346.GK23584@kadam/Reported-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190829163827.203274-1-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

EROFS filesystem has been merged into linux-staging for a year.

EROFS is designed to be a better solution of saving extra storage
space with guaranteed end-to-end performance for read-only files
with the help of reduced metadata, fixed-sized output compression
and decompression inplace technologies.

In the past year, EROFS was greatly improved by many people as
a staging driver, self-tested, betaed by a large number of our
internal users, successfully applied to almost all in-service
HUAWEI smartphones as the part of EMUI 9.1 and proven to be stable
enough to be moved out of staging.

EROFS is a self-contained filesystem driver. Although there are
still some TODOs to be more generic, we have a dedicated team
actively keeping on working on EROFS in order to make it better
with the evolution of Linux kernel as the other in-kernel filesystems.

As Pavel suggested, it's better to do as one commit since git
can do moves and all histories will be saved in this way.

Let's promote it from staging and enhance it more actively as
a "real" part of kernel for more wider scenarios!

Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Pavel Machek <pavel@denx.de>
Cc: David Sterba <dsterba@suse.cz>
Cc: Amir Goldstein <amir73il@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Darrick J . Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Richard Weinberger <richard@nod.at>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: Li Guifu <bluce.liguifu@huawei.com>
Cc: Fang Wei <fangwei1@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190822213659.5501-1-hsiangkao@aol.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As reported by erofs-utils fuzzer, currently, multiref
(ondisk deduplication) hasn't been supported for now,
we should forbid it properly.

Fixes: 3883a79a ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190821140152.229648-1-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As reported by erofs-utils fuzzer, 2 conditions
can happen in corrupted images, which can cause
unexpected behaviors.
 - access the same pcluster one more time;
 - access the tail end pcluster again, e.g.
            _ access again (will trigger tail merging)
           |
     1 2 3 1 2             ->   1 2 3 1
     |_ tail end of the chain    \___/ (unexpected behavior)
Let's detect and avoid them now.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190821030908.40282-1-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As reported by erofs-utils fuzzer, these error handling
path will be entered to handle corrupted images.

Lack of erofs_workgroup_puts will cause unmounting
unsuccessfully.

Fix these return values to EFSCORRUPTED as well.

Fixes: 3883a79a ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190819103426.87579-4-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

As reported by erofs_utils fuzzer, a logical page can belong
to at most 2 compressed clusters, if one compressed cluster
is corrupted, but the other has been ready in submitting chain.

The chain needs to submit anyway in order to keep the page
working properly (page unlocked with PG_error set, PG_uptodate
not set).

Let's fix it now.

Fixes: 3883a79a ("staging: erofs: introduce VLE decompression support")
Cc: <stable@vger.kernel.org> # 4.19+
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Link: https://lore.kernel.org/r/20190819103426.87579-2-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Kill all kconfig cache strategies and turn them into mount options
"cache_strategy={disable|readahead|readaround}".

As the first step, cached pages can still be usable after cache
is disabled by remounting, and these pages will be fallen out
over time, which can be refined in the later version if some
requirement is needed. Update related document as well.
Suggested-by: NTheodore Ts'o <tytso@mit.edu>
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-20-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Although this patch has an amount of changes, it is hard to
separate into smaller patches.

Most changes are due to structure renaming for better understand
and straightforward,
 z_erofs_vle_workgroup to z_erofs_pcluster
             since it represents a physical cluster;
 z_erofs_vle_work to z_erofs_collection
             since it represents a collection of logical pages;
 z_erofs_vle_work_builder to z_erofs_collector
             since it's used to fill z_erofs_{pcluster,collection}.

struct z_erofs_vle_work_finder has no extra use compared with
struct z_erofs_collector, delete it.

FULL_LENGTH bit is integrated into .length of pcluster so that it
can be updated with the corresponding length change in atomic.

Minor, add comments for better description.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-18-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

- use shorter function names:
  z_erofs_pagevec_enqueue and z_erofs_pagevec_dequeue;
- minor code cleanup.

In order to keep in line with erofs-outofstaging patchset.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-16-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

remove duplicated code in decompressor by introducing
failable erofs_allocpage().
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-14-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

Tidy up relative order of variables / declarations in internal.h,
move some local static functions out into other files and
add tags at the end of #endif acrossing several lines.

No logic change.
Reviewed-by: NChao Yu <yuchao0@huawei.com>
Signed-off-by: NGao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20190731155752.210602-7-gaoxiang25@huawei.comSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>