linux/fs/hfs
Fabio M. De Francesco 21490eff12 hfs: replace kmap() with kmap_local_page() in btree.c
kmap() is being deprecated in favor of kmap_local_page().

Two main problems with kmap(): (1) It comes with an overhead as mapping
space is restricted and protected by a global lock for synchronization and
(2) it also requires global TLB invalidation when the kmap's pool wraps
and it might block when the mapping space is fully utilized until a slot
becomes available.

With kmap_local_page() the mappings are per thread, CPU local, can take
page faults, and can be called from any context (including interrupts). 
It is faster than kmap() in kernels with HIGHMEM enabled.  Furthermore,
the tasks can be preempted and, when they are scheduled to run again, the
kernel virtual addresses are restored and still valid.

Since its use in btree.c is safe everywhere, it should be preferred.

Therefore, replace kmap() with kmap_local_page() in btree.c.  Where
possible, use the suited standard helpers (memzero_page(), memcpy_page())
instead of open coding kmap_local_page() plus memset() or memcpy().

Tested in a QEMU/KVM x86_32 VM, 6GB RAM, booting a kernel with
HIGHMEM64GB enabled.

Link: https://lkml.kernel.org/r/20220821180400.8198-4-fmdefrancesco@gmail.com
Signed-off-by: Fabio M. De Francesco <fmdefrancesco@gmail.com>
Suggested-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Viacheslav Dubeyko <slava@dubeyko.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Chaitanya Kulkarni <kch@nvidia.com>
Cc: Christian Brauner (Microsoft) <brauner@kernel.org>
Cc: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Cc: Jeff Layton <jlayton@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Kees Cook <keescook@chromium.org>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-09-11 21:55:09 -07:00
..
attr.c acl: handle idmapped mounts 2021-01-24 14:27:17 +01:00
bfind.c hfs: add lock nesting notation to hfs_find_init 2021-07-15 10:13:49 -07:00
bitmap.c
bnode.c hfs: replace kmap() with kmap_local_page() in bnode.c 2022-09-11 21:55:08 -07:00
brec.c hfs: fix BUG on bnode parent update 2018-10-31 08:54:13 -07:00
btree.c hfs: replace kmap() with kmap_local_page() in btree.c 2022-09-11 21:55:09 -07:00
btree.h hfs: add lock nesting notation to hfs_find_init 2021-07-15 10:13:49 -07:00
catalog.c hfs: prevent btree data loss on ENOSPC 2018-10-31 08:54:13 -07:00
dir.c fs: make helpers idmap mount aware 2021-01-24 14:27:20 +01:00
extent.c hfs: Call hfs_write_begin() and generic_write_end() directly 2022-05-08 14:45:56 -04:00
hfs_fs.h hfs: Call hfs_write_begin() and generic_write_end() directly 2022-05-08 14:45:56 -04:00
hfs.h
inode.c fs: Change try_to_free_buffers() to take a folio 2022-05-09 23:12:34 -04:00
Kconfig docs: filesystems: fix renamed references 2020-04-20 15:45:22 -06:00
Makefile treewide: Add SPDX license identifier - Makefile/Kconfig 2019-05-21 10:50:46 +02:00
mdb.c block: remove genhd.h 2022-02-02 07:49:59 -07:00
part_tbl.c
string.c get rid of 'parent' argument of ->d_compare() 2016-07-31 16:37:25 -04:00
super.c fs: allocate inode by using alloc_inode_sb() 2022-03-22 15:57:03 -07:00
sysdep.c
trans.c qstr: constify instances in hfs 2016-07-20 23:30:06 -04:00