f2fs: updates on 4.15-rc1

Pull f2fs updates from Jaegeuk Kim:
"In this round, we introduce sysfile-based quota support which is
required for Android by default. In addition, we allow that users are
able to reserve some blocks in runtime to mitigate performance drops
in low free space.

Enhancements:
 - assign proper data segments according to write_hints given by user
 - issue cache_flush on dirty devices only among multiple devices
 - exploit cp_error flag and add more faults to enhance fault
   injection test
 - conduct more readaheads during f2fs_readdir
 - add a range for discard commands

Bug fixes:
 - fix zero stat->st_blocks when inline_data is set
 - drop crypto key and free stale memory pointer while evict_inode is
   failing
 - fix some corner cases in free space and segment management
 - fix wrong last_disk_size

This series includes lots of clean-ups and code enhancement in terms
of xattr operations, discard/flush command control. In addition, it
adds versatile debugfs entries to monitor f2fs status"

Cherry-picked from origin/upstream-f2fs-stable-linux-4.14.y:

7b538c1c f2fs: deny accessing encryption policy if encryption is off
c43ffa18 f2fs: inject fault in inc_valid_node_count
fa73e874 f2fs: expose quota information in debugfs
eb538327 f2fs: separate nat entry mem alloc from nat_tree_lock
a7c6829c f2fs: validate before set/clear free nat bitmap
eb84a567 f2fs: avoid opened loop codes in __add_ino_entry
793cdb93 f2fs: apply write hints to select the type of segments for buffered write
75a69567 f2fs: introduce scan_curseg_cache for cleanup
6180b68c f2fs: optimize the way of traversing free_nid_bitmap
221656e4 f2fs: keep scanning until enough free nids are acquired
0b0a1e72 f2fs: trace checkpoint reason in fsync()
af75a621 f2fs: keep isize once block is reserved cross EOF
3b96799d f2fs: avoid race in between GC and block exchange
c33a70d7 f2fs: save a multiplication for last_nid calculation
4c8fdcd5 f2fs: fix summary info corruption
ff95a94d f2fs: remove dead code in update_meta_page
c7f08b50 f2fs: remove unneeded semicolon
91d56034 f2fs: don't bother with inode->i_version
270e78cf f2fs: check curseg space before foreground GC
d3ad907d f2fs: use rw_semaphore to protect SIT cache
d9e1a6b6 f2fs: support quota sys files
3aec74eb f2fs: add quota_ino feature infra
cf943558 f2fs: optimize __update_nat_bits
e56a876f f2fs: modify for accurate fggc node io stat
a39d96b9 Revert "f2fs: handle dirty segments inside refresh_sit_entry"
0ccccb38 f2fs: add a function to move nid
cd3b86fc f2fs: export SSR allocation threshold
ca50229b f2fs: give correct trimmed blocks in fstrim
73b8db88 f2fs: support bio allocation error injection
b8a938e4 f2fs: support get_page error injection
f2b91f22 f2fs: add missing sysfs description
6cef5570 f2fs: support soft block reservation
cef5e716 f2fs: handle error case when adding xattr entry
a7848c0d f2fs: support flexible inline xattr size
c6314306 f2fs: show current cp state
032d1409 f2fs: add missing quota_initialize
f241f66c f2fs: show # of dirty segments via sysfs
1687d9f0 f2fs: stop all the operations by cp_error flag
f793a2c2 f2fs: remove several redundant assignments
fb000836 f2fs: avoid using timespec
a4b9ed20 f2fs: fix to correct no_fggc_candidate
bc69d560 Revert "f2fs: return wrong error number on f2fs_quota_write"
f49f4124 f2fs: remove obsolete pointer for truncate_xattr_node
c6bfa17c f2fs: retry ENOMEM for quota_read|write
5e14327f f2fs: limit # of inmemory pages
a064458a f2fs: update ctx->pos correctly when hitting hole in directory
372b93f9 f2fs: relocate readahead codes in readdir()
457e9c03 f2fs: allow readdir() to be interrupted
2d1af27c f2fs: trace f2fs_readdir
7bbdc74b f2fs: trace f2fs_lookup
76e8f606 f2fs: skip searching non-exist range in truncate_hole
2f18884d f2fs: avoid stale fi->gdirty_list pointer
0dbf4fd4 f2fs/crypto: drop crypto key at evict_inode only
8c582763 f2fs: fix to avoid race when accessing last_disk_size
c2e2eec6 f2fs: Fix bool initialization/comparison
ab0a7977 f2fs: give up CP_TRIMMED_FLAG if it drops discards
001cc0b0 f2fs: trace f2fs_remove_discard
c72699d2 f2fs: reduce cmd_lock coverage in __issue_discard_cmd
0eeceeb2 f2fs: split discard policy
775d0e58 f2fs: wrap discard policy
77b5bf3a f2fs: support issuing/waiting discard in range
6b50d3ec f2fs: fix to flush multiple device in checkpoint
5483b178 f2fs: enhance multiple device flush
06800576 f2fs: fix to show ino management cache size correctly
a815ce99 f2fs: drop FI_UPDATE_WRITE tag after f2fs_issue_flush
3257c657 f2fs: obsolete ALLOC_NID_LIST list
d54bf9da f2fs: convert inline data for direct I/O & FI_NO_PREALLOC
32c57300 f2fs: allow readpages with NULL file pointer
dba2b454 f2fs: show flush list status in sysfs
fae7dc47 f2fs: introduce read_xattr_block
148edd02 f2fs: introduce read_inline_xattr
b735df5e Revert "f2fs: reuse nids more aggressively"
13e34cba Revert "f2fs: node segment is prior to data segment selected victim"
a76d81af f2fs: fix to clear FI_NO_PREALLOC

Bug: 70801385
Change-Id: I3b8e0c21f4f8d52b669776fce41df77a4363d473
Signed-off-by: Jaegeuk Kim <jaegeuk@google.com>