As Jiqun Li reported in bugzilla:
https://bugzilla.kernel.org/show_bug.cgi?id=202747
System can panic due to using wrong allocate/free function pair
in xattr interface:
- use kvmalloc to allocate memory
- use kzfree to free memory
Let's fix to use kvfree instead of kzfree, BTW, we are safe to
get rid of kzfree, since there is no such confidential data stored
as xattr, we don't need to zero it before free memory.
Fixes: 5222595d09 ("f2fs: use kvmalloc, if kmalloc is failed")
Reported-by: Jiqun Li <jiqun.li@unisoc.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
As Seulbae Kim reported in bugzilla:
https://bugzilla.kernel.org/show_bug.cgi?id=202637
We didn't recover permission field correctly after sudden power-cut,
the reason is in setattr we didn't add inode into global dirty list
once i_mode is changed, so latter checkpoint triggered by fsync will
not flush last i_mode into disk, result in this problem, fix it.
Reported-by: Seulbae Kim <seulbae@gatech.edu>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This follows to give random number to i_generation along with commit
2325306802 ("ext4: improve smp scalability for inode generation")
This can be used for DUN for UFS HW encryption.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
VFS will take inode_lock for readdir, therefore no need to
take page lock in readdir at all just as the majority of
other generic filesystems.
This patch improves concurrency since .iterate_shared
was introduced to VFS years ago.
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In error path of IPU, we didn't account iostat correctly, fix it.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
For IPU path of f2fs_do_write_data_page(), in its error path, we
need to release encrypted page and fscrypt context, otherwise it
will cause memory leak.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This patch changes to allow failure of f2fs_bio_alloc() in
__submit_flush_wait(), which can simulate flush error in checkpoint()
for covering more error paths.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
With current retry mechanism in f2fs_fill_super, first fill_super
fails due to no memory, then second fill_super runs w/o recovery,
if we succeed, we may lose fsynced data, it doesn't make sense.
Let's retry fill_super only if it occurs non-ENOMEM error during
recovery.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Note that __GFP_ZERO is not supported for mempool_alloc,
which also documented in the mempool_alloc comments.
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
If we met this once, let fsck.f2fs clear this only.
Note that, this addresses all the subtle fault injection test.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
As Dan reported:
"We put an upper bound on ->write_io_size_bits but we don't have a lower
bound."
So let's add lower bound check for ->write_io_size_bits in parse_options().
[We don't allow configuring ->write_io_size_bits to zero, since at least
we need to fill one dummy page for aligned IO.]
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
We use below condition to check inline_xattr_size boundary:
if (!F2FS_OPTION(sbi).inline_xattr_size ||
F2FS_OPTION(sbi).inline_xattr_size >=
DEF_ADDRS_PER_INODE -
F2FS_TOTAL_EXTRA_ATTR_SIZE -
DEF_INLINE_RESERVED_SIZE -
DEF_MIN_INLINE_SIZE)
There is there problems in that check:
- we should allow inline_xattr_size equaling to min size of inline
{data,dentry} area.
- F2FS_TOTAL_EXTRA_ATTR_SIZE and inline_xattr_size are based on
different size unit, previous one is 4 bytes, latter one is 1 bytes.
- DEF_MIN_INLINE_SIZE only indicate min size of inline data area,
however, we need to consider min size of inline dentry area as well,
minimal inline dentry should at least contain two entries: '.' and
'..', so that min inline_dentry size is 40 bytes.
.bitmap 1 * 1 = 1
.reserved 1 * 1 = 1
.dentry 11 * 2 = 22
.filename 8 * 2 = 16
total 40
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Fix below warning coming because of using mutex lock in atomic context.
BUG: sleeping function called from invalid context at kernel/locking/mutex.c:98
in_atomic(): 1, irqs_disabled(): 0, pid: 585, name: sh
Preemption disabled at: __radix_tree_preload+0x28/0x130
Call trace:
dump_backtrace+0x0/0x2b4
show_stack+0x20/0x28
dump_stack+0xa8/0xe0
___might_sleep+0x144/0x194
__might_sleep+0x58/0x8c
mutex_lock+0x2c/0x48
f2fs_trace_pid+0x88/0x14c
f2fs_set_node_page_dirty+0xd0/0x184
Do not use f2fs_radix_tree_insert() to avoid doing cond_resched() with
spin_lock() acquired.
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Previously, we changed lock from cp_rwsem to node_change, it solved
the deadlock issue which was caused by below race condition:
Thread A Thread B
- f2fs_setattr
- f2fs_lock_op -- read_lock
- dquot_transfer
- __dquot_transfer
- dquot_acquire
- commit_dqblk
- f2fs_quota_write
- f2fs_write_begin
- f2fs_write_failed
- write_checkpoint
- block_operations
- f2fs_lock_all -- write_lock
- f2fs_truncate_blocks
- f2fs_lock_op -- read_lock
But it breaks the sematics of cp_rwsem, in other callers like:
- f2fs_file_write_iter -> f2fs_write_begin -> f2fs_write_failed
- f2fs_direct_IO -> f2fs_write_failed
We allow to truncate dnode w/o cp_rwsem held, result in incorrect sit
bitmap update, which can cause further data corruption.
So this patch reverts previous fix implementation, and try to fix
deadlock by skipping calling f2fs_truncate_blocks() in f2fs_write_failed()
only for quota file, and keep the preallocated data/node in the tail of
quota file, we can expecte that the preallocated space can be used to
store quota info latter soon.
Fixes: af033b2aa8 ("f2fs: guarantee journalled quota data by checkpoint")
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
When sb->s_root is NULL dput() will do nothing,
so jump to label 'free_node_inode' instead of lable
'free_root_inode' when failing from d_make_root().
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
We missed to add document for inline_xattr_size mount option in f2fs.txt,
add it.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
v4: Rearrange the previous three versions.
The following scenario could lead to data block override by mistake.
TASK A | TASK kworker | TASK B | TASK C
| | |
open | | |
write | | |
close | | |
| f2fs_write_data_pages | |
| f2fs_write_cache_pages | |
| f2fs_outplace_write_data | |
| f2fs_allocate_data_block (get block in seg S, | |
| S is full, and only | |
| have this valid data | |
| block) | |
| allocate_segment | |
| locate_dirty_segment (mark S as PRE) | |
| f2fs_submit_page_write (submit but is not | |
| written on dev) | |
unlink | | |
iput_final | | |
f2fs_drop_inode | | |
f2fs_truncate | | |
(not evict) | | |
| | write_checkpoint |
| | flush merged bio but not wait file data writeback |
| | set_prefree_as_free (mark S as FREE) |
| | | update NODE/DATA
| | | allocate_segment (select S)
| writeback done | |
So we need to guarantee io complete before truncate inode in f2fs_drop_inode.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Zheng Liang <zhengliang6@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Let's use xattr_prefix instead of open code.
No logic changes.
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Some works after roll-forward recovery can get an error which will release
all the data structures. Let's flush them in order to make it clean.
One possible corruption came from:
[ 90.400500] list_del corruption. prev->next should be ffffffed1f566208, but was (null)
[ 90.675349] Call trace:
[ 90.677869] __list_del_entry_valid+0x94/0xb4
[ 90.682351] remove_dirty_inode+0xac/0x114
[ 90.686563] __f2fs_write_data_pages+0x6a8/0x6c8
[ 90.691302] f2fs_write_data_pages+0x40/0x4c
[ 90.695695] do_writepages+0x80/0xf0
[ 90.699372] __writeback_single_inode+0xdc/0x4ac
[ 90.704113] writeback_sb_inodes+0x280/0x440
[ 90.708501] wb_writeback+0x1b8/0x3d0
[ 90.712267] wb_workfn+0x1a8/0x4d4
[ 90.715765] process_one_work+0x1c0/0x3d4
[ 90.719883] worker_thread+0x224/0x344
[ 90.723739] kthread+0x120/0x130
[ 90.727055] ret_from_fork+0x10/0x18
Reported-by: Sahitya Tummala <stummala@codeaurora.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
After quota_off, we'll get some dirty blocks. If put_super don't have a chance
to flush them by checkpoint, it causes NULL pointer exception in end_io after
iput(node_inode). (e.g., by checkpoint=disable)
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Otherwise, it wakes up discard thread which will sleep again by busy IOs
in a loop.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
If every discard were issued successfully, we can avoid further discard.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This mode returns mount() quickly with EAGAIN. We can trigger this by
shutdown(F2FS_GOING_DOWN_NEED_FSCK).
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
When we umount f2fs, we need to avoid long delay due to discard commands, which
is actually taking tens of seconds, if storage is very slow on UNMAP. So, this
patch introduces timeout-based work on it.
By default, let me give 5 seconds for discard.
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
In order to record direct IO count, we add two additional type in
enum count_type: F2FS_DIO_{WRITE,READ}, but those IO won't dirty
filesystem metadata, so we don't need to set filesystem dirty in
inc_page_count(), fix it.
Fixes: 02b16d0a34 ("f2fs: add to account direct IO")
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
As Dan Carpenter as below:
The patch df634f444ee9: "f2fs: use rb_*_cached friends" from Oct 4,
2018, leads to the following static checker warning:
fs/f2fs/extent_cache.c:606 f2fs_update_extent_tree_range()
error: uninitialized symbol 'leftmost'.
And also Eric Biggers, and Kyungtae Kim reported, there is an UBSAN
warning described as below:
We report a bug in linux-4.20.2: "UBSAN: Undefined behaviour in
fs/f2fs/extent_cache.c"
kernel config: https://kt0755.github.io/etc/config_v4.20_stable
repro: https://kt0755.github.io/etc/repro.4a3e7.c (f2fs is mounted on
/mnt/f2fs/)
This arose in f2fs_update_extent_tree_range (fs/f2fs/extent_cache.c:605).
It seems that, for some reason, its last argument became "24"
although that was supposed to be bool type.
=========================================
UBSAN: Undefined behaviour in fs/f2fs/extent_cache.c:605:4
load of value 24 is not a valid value for type '_Bool'
CPU: 0 PID: 6774 Comm: syz-executor5 Not tainted 4.20.2 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xb1/0x118 lib/dump_stack.c:113
ubsan_epilogue+0x12/0x94 lib/ubsan.c:159
__ubsan_handle_load_invalid_value+0x17a/0x1be lib/ubsan.c:457
f2fs_update_extent_tree_range+0x1d4a/0x1d50 fs/f2fs/extent_cache.c:605
f2fs_update_extent_cache+0x2b6/0x350 fs/f2fs/extent_cache.c:804
f2fs_update_data_blkaddr+0x61/0x70 fs/f2fs/data.c:656
f2fs_outplace_write_data+0x1d6/0x4b0 fs/f2fs/segment.c:3140
f2fs_convert_inline_page+0x86d/0x2060 fs/f2fs/inline.c:163
f2fs_convert_inline_inode+0x6b5/0xad0 fs/f2fs/inline.c:208
f2fs_preallocate_blocks+0x78b/0xb00 fs/f2fs/data.c:982
f2fs_file_write_iter+0x31b/0xf40 fs/f2fs/file.c:3062
call_write_iter include/linux/fs.h:1857 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x538/0x6e0 fs/read_write.c:487
vfs_write+0x1b3/0x520 fs/read_write.c:549
ksys_write+0xde/0x1c0 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__x64_sys_write+0x7e/0xc0 fs/read_write.c:607
do_syscall_64+0xbe/0x4f0 arch/x86/entry/common.c:290
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4497b9
Code: e8 8c 9f 02 00 48 83 c4 18 c3 0f 1f 80 00 00 00 00 48 89 f8 48
89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d
01 f0 ff ff 0f 83 9b 6b fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f1ea15edc68 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f1ea15ee6cc RCX: 00000000004497b9
RDX: 0000000000001000 RSI: 0000000020000140 RDI: 0000000000000013
RBP: 000000000071bea0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 000000000000bb50 R14: 00000000006f4bf0 R15: 00007f1ea15ee700
=========================================
As I checked, this uninitialized variable won't cause extent cache
corruption, but in order to avoid such kind of warning of both UBSAN
and smatch, fix to initialize related variable.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Reported-by: Eric Biggers <ebiggers@google.com>
Reported-by: Kyungtae Kim <kt0755@gmail.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Dentry bitmap is not enough to detect incorrect dentries. So this patch
also checks the namelen value of a dentry.
Signed-off-by: Gong Chen <gongchen4@huawei.com>
Signed-off-by: Sheng Yong <shengyong1@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
While traversing dirents in f2fs_fill_dentries(), if bitmap is valid,
filename length should not be zero, otherwise, directory structure
consistency could be corrupted, in this case, let's print related
info and set SBI_NEED_FSCK to trigger fsck for repairing.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.
Cc: Jaegeuk Kim <jaegeuk@kernel.org>
Cc: Chao Yu <yuchao0@huawei.com>
Cc: linux-f2fs-devel@lists.sourceforge.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Type of inject_rate is unsigned int, let's check new value's
validity during configuring.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Fixes gcc '-Wunused-but-set-variable' warning:
fs/f2fs/data.c: In function 'f2fs_dio_submit_bio':
fs/f2fs/data.c:2585:6: warning:
variable 'err' set but not used [-Wunused-but-set-variable]
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
The error case of failing allocating memory should
return -ENOMEM.
Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This fixes wrong access of address spaces of node and meta inodes after iput.
Fixes: 60aa4d5536 ("f2fs: fix use-after-free issue when accessing sbi->stat_info")
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Otherwise, we can get wrong counts incurring checkpoint hang.
IO_W (CP: -24, Data: 24, Flush: ( 0 0 1), Discard: ( 0 0))
Thread A Thread B
- f2fs_write_data_pages
- __write_data_page
- f2fs_submit_page_write
- inc_page_count(F2FS_WB_DATA)
type is F2FS_WB_DATA due to file is non-atomic one
- f2fs_ioc_start_atomic_write
- set_inode_flag(FI_ATOMIC_FILE)
- f2fs_write_end_io
- dec_page_count(F2FS_WB_CP_DATA)
type is F2FS_WB_DATA due to file becomes
atomic one
Cc: <stable@vger.kernel.org>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
For some reasons, I accidentally got rid of "generic-y += shmparam.h"
from some architectures.
Restore them to fix building c6x, h8300, hexagon, m68k, microblaze,
openrisc, and unicore32.
Fixes: d6e4b3e326 ("arch: remove redundant UAPI generic-y defines")
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
- improve boolinit.cocci and use_after_iter.cocci semantic patches
- fix alignment for kallsyms
- move 'asm goto' compiler test to Kconfig and clean up jump_label
CONFIG option
- generate asm-generic wrappers automatically if arch does not implement
mandatory UAPI headers
- remove redundant generic-y defines
- misc cleanups
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Merge tag 'kbuild-v4.21-3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild
Pull more Kbuild updates from Masahiro Yamada:
- improve boolinit.cocci and use_after_iter.cocci semantic patches
- fix alignment for kallsyms
- move 'asm goto' compiler test to Kconfig and clean up jump_label
CONFIG option
- generate asm-generic wrappers automatically if arch does not
implement mandatory UAPI headers
- remove redundant generic-y defines
- misc cleanups
* tag 'kbuild-v4.21-3' of git://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild:
kconfig: rename generated .*conf-cfg to *conf-cfg
kbuild: remove unnecessary stubs for archheader and archscripts
kbuild: use assignment instead of define ... endef for filechk_* rules
arch: remove redundant UAPI generic-y defines
kbuild: generate asm-generic wrappers if mandatory headers are missing
arch: remove stale comments "UAPI Header export list"
riscv: remove redundant kernel-space generic-y
kbuild: change filechk to surround the given command with { }
kbuild: remove redundant target cleaning on failure
kbuild: clean up rule_dtc_dt_yaml
kbuild: remove UIMAGE_IN and UIMAGE_OUT
jump_label: move 'asm goto' support test to Kconfig
kallsyms: lower alignment on ARM
scripts: coccinelle: boolinit: drop warnings on named constants
scripts: coccinelle: check for redeclaration
kconfig: remove unused "file" field of yylval union
nds32: remove redundant kernel-space generic-y
nios2: remove unneeded HAS_DMA define
Pull perf tooling updates form Ingo Molnar:
"A final batch of perf tooling changes: mostly fixes and small
improvements"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (29 commits)
perf session: Add comment for perf_session__register_idle_thread()
perf thread-stack: Fix thread stack processing for the idle task
perf thread-stack: Allocate an array of thread stacks
perf thread-stack: Factor out thread_stack__init()
perf thread-stack: Allow for a thread stack array
perf thread-stack: Avoid direct reference to the thread's stack
perf thread-stack: Tidy thread_stack__bottom() usage
perf thread-stack: Simplify some code in thread_stack__process()
tools gpio: Allow overriding CFLAGS
tools power turbostat: Override CFLAGS assignments and add LDFLAGS to build command
tools thermal tmon: Allow overriding CFLAGS assignments
tools power x86_energy_perf_policy: Override CFLAGS assignments and add LDFLAGS to build command
perf c2c: Increase the HITM ratio limit for displayed cachelines
perf c2c: Change the default coalesce setup
perf trace beauty ioctl: Beautify USBDEVFS_ commands
perf trace beauty: Export function to get the files for a thread
perf trace: Wire up ioctl's USBDEBFS_ cmd table generator
perf beauty ioctl: Add generator for USBDEVFS_ ioctl commands
tools headers uapi: Grab a copy of usbdevice_fs.h
perf trace: Store the major number for a file when storing its pathname
...
The semantics of what "in core" means for the mincore() system call are
somewhat unclear, but Linux has always (since 2.3.52, which is when
mincore() was initially done) treated it as "page is available in page
cache" rather than "page is mapped in the mapping".
The problem with that traditional semantic is that it exposes a lot of
system cache state that it really probably shouldn't, and that users
shouldn't really even care about.
So let's try to avoid that information leak by simply changing the
semantics to be that mincore() counts actual mapped pages, not pages
that might be cheaply mapped if they were faulted (note the "might be"
part of the old semantics: being in the cache doesn't actually guarantee
that you can access them without IO anyway, since things like network
filesystems may have to revalidate the cache before use).
In many ways the old semantics were somewhat insane even aside from the
information leak issue. From the very beginning (and that beginning is
a long time ago: 2.3.52 was released in March 2000, I think), the code
had a comment saying
Later we can get more picky about what "in core" means precisely.
and this is that "later". Admittedly it is much later than is really
comfortable.
NOTE! This is a real semantic change, and it is for example known to
change the output of "fincore", since that program literally does a
mmmap without populating it, and then doing "mincore()" on that mapping
that doesn't actually have any pages in it.
I'm hoping that nobody actually has any workflow that cares, and the
info leak is real.
We may have to do something different if it turns out that people have
valid reasons to want the old semantics, and if we can limit the
information leak sanely.
Cc: Kevin Easton <kevin@guarana.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Masatake YAMATO <yamato@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
