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Presently we start garbage collection late - when we start running
out of free zones to backfill max_open_zones. This is a reasonable
default as it minimizes write amplification. The longer we wait,
the more blocks are invalidated and reclaim cost less in terms
of blocks to relocate.
Starting this late however introduces a risk of GC being outcompeted
by user writes. If GC can't keep up, user writes will be forced to
wait for free zones with high tail latencies as a result.
This is not a problem under normal circumstances, but if fragmentation
is bad and user write pressure is high (multiple full-throttle
writers) we will "bottom out" of free zones.
To mitigate this, introduce a zonegc_low_space tunable that lets the
user specify a percentage of how much of the unused space that GC
should keep available for writing. A high value will reclaim more of
the space occupied by unused blocks, creating a larger buffer against
write bursts.
This comes at a cost as write amplification is increased. To
illustrate this using a sample workload, setting zonegc_low_space to
60% avoids high (500ms) max latencies while increasing write
amplification by 15%.
Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_buf_free can call vunmap, which can sleep. The vunmap path is an
unlikely one, so add might_sleep to ensure calling xfs_buf_free from
atomic context gets caught more easily.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Marking a log item as failed kept a buffer reference around for
resubmission of inode and dquote items.
For inode items commit 298f7bec503f3 ("xfs: pin inode backing buffer to
the inode log item") started pinning the inode item buffers
unconditionally and removed the need for this. Later commit acc8f8628c37
("xfs: attach dquot buffer to dquot log item buffer") did the same for
dquot items but didn't fully clean up the xfs_clear_li_failed side
for them. Stop adding the extra pin for dquot items and remove the
helpers.
This happens to fix a call to xfs_buf_free with the AIL lock held,
which would be incorrect for the unlikely case freeing the buffer
ends up calling vfree.
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Carlos Maiolino <cmaiolino@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Syzkaller detected a use-after-free issue in ext4_insert_dentry that was
caused by out-of-bounds access due to incorrect splitting in do_split.
BUG: KASAN: use-after-free in ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2109
Write of size 251 at addr ffff888074572f14 by task syz-executor335/5847
CPU: 0 UID: 0 PID: 5847 Comm: syz-executor335 Not tainted 6.12.0-rc6-syzkaller-00318-ga9cda7c0ffed #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/30/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:377 [inline]
print_report+0x169/0x550 mm/kasan/report.c:488
kasan_report+0x143/0x180 mm/kasan/report.c:601
kasan_check_range+0x282/0x290 mm/kasan/generic.c:189
__asan_memcpy+0x40/0x70 mm/kasan/shadow.c:106
ext4_insert_dentry+0x36a/0x6d0 fs/ext4/namei.c:2109
add_dirent_to_buf+0x3d9/0x750 fs/ext4/namei.c:2154
make_indexed_dir+0xf98/0x1600 fs/ext4/namei.c:2351
ext4_add_entry+0x222a/0x25d0 fs/ext4/namei.c:2455
ext4_add_nondir+0x8d/0x290 fs/ext4/namei.c:2796
ext4_symlink+0x920/0xb50 fs/ext4/namei.c:3431
vfs_symlink+0x137/0x2e0 fs/namei.c:4615
do_symlinkat+0x222/0x3a0 fs/namei.c:4641
__do_sys_symlink fs/namei.c:4662 [inline]
__se_sys_symlink fs/namei.c:4660 [inline]
__x64_sys_symlink+0x7a/0x90 fs/namei.c:4660
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
The following loop is located right above 'if' statement.
for (i = count-1; i >= 0; i--) {
/* is more than half of this entry in 2nd half of the block? */
if (size + map[i].size/2 > blocksize/2)
break;
size += map[i].size;
move++;
}
'i' in this case could go down to -1, in which case sum of active entries
wouldn't exceed half the block size, but previous behaviour would also do
split in half if sum would exceed at the very last block, which in case of
having too many long name files in a single block could lead to
out-of-bounds access and following use-after-free.
Found by Linux Verification Center (linuxtesting.org) with Syzkaller.
Cc: stable@vger.kernel.org
Fixes: 5872331b3d91 ("ext4: fix potential negative array index in do_split()")
Signed-off-by: Artem Sadovnikov <a.sadovnikov@ispras.ru>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250404082804.2567-3-a.sadovnikov@ispras.ru
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Block validity checks need to be skipped in case they are called
for journal blocks since they are part of system's protected
zone.
Currently, this is done by checking inode->ino against
sbi->s_es->s_journal_inum, which is a direct read from the ext4 sb
buffer head. If someone modifies this underneath us then the
s_journal_inum field might get corrupted. To prevent against this,
change the check to directly compare the inode with journal->j_inode.
**Slight change in behavior**: During journal init path,
check_block_validity etc might be called for journal inode when
sbi->s_journal is not set yet. In this case we now proceed with
ext4_inode_block_valid() instead of returning early. Since systems zones
have not been set yet, it is okay to proceed so we can perform basic
checks on the blocks.
Suggested-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/0c06bc9ebfcd6ccfed84a36e79147bf45ff5adc1.1743142920.git.ojaswin@linux.ibm.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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-Wflex-array-member-not-at-end was introduced in GCC-14, and we are
getting ready to enable it, globally.
Use the `DEFINE_RAW_FLEX()` helper for an on-stack definition of
a flexible structure where the size of the flexible-array member
is known at compile-time, and refactor the rest of the code,
accordingly.
So, with these changes, fix the following warning:
fs/ext4/mballoc.c:3041:40: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
Reviewed-by: Kees Cook <kees@kernel.org>
Link: https://patch.msgid.link/Z-SF97N3AxcIMlSi@kspp
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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Documentation and implementation of the ext4 super block have
slightly diverged: Padding has been removed in order to make room for
new fields that are still missing in the documentation.
Add the new fields s_encryption_level, s_first_error_errorcode,
s_last_error_errorcode to the documentation of the ext4 super block.
Fixes: f542fbe8d5e8 ("ext4 crypto: reserve codepoints used by the ext4 encryption feature")
Fixes: 878520ac45f9 ("ext4: save the error code which triggered an ext4_error() in the superblock")
Signed-off-by: Tom Vierjahn <tom.vierjahn@acm.org>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Link: https://patch.msgid.link/20250324221004.5268-1-tom.vierjahn@acm.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
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When rv_is_container_monitor() is called on the last monitor in
rv_monitors_list, KASAN yells:
BUG: KASAN: global-out-of-bounds in rv_is_container_monitor+0x101/0x110
Read of size 8 at addr ffffffff97c7c798 by task setup/221
The buggy address belongs to the variable:
rv_monitors_list+0x18/0x40
This is due to list_next_entry() is called on the last entry in the list.
It wraps around to the first list_head, and the first list_head is not
embedded in struct rv_monitor_def.
Fix it by checking if the monitor is last in the list.
Cc: stable@vger.kernel.org
Cc: Gabriele Monaco <gmonaco@redhat.com>
Fixes: cb85c660fcd4 ("rv: Add option for nested monitors and include sched")
Link: https://lore.kernel.org/e85b5eeb7228bfc23b8d7d4ab5411472c54ae91b.1744355018.git.namcao@linutronix.de
Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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The retval and retaddr options for function_graph tracer will add a
comment at the end of a function for both leaf and non leaf functions that
looks like:
__wake_up_common(); /* ret=0x1 */
} /* pick_next_task_fair ret=0x0 */
The function print_graph_retval() adds a newline after the "*/". But if
that's not called, the caller function needs to make sure there's a
newline added.
This is confusing and when the function parameters code was added, it
added a newline even when calling print_graph_retval() as the fact that
the print_graph_retval() function prints a newline isn't obvious.
This caused an extra newline to be printed and that made it fail the
selftests when the retval option was set, as the selftests were not
expecting blank lines being injected into the trace.
Instead of having print_graph_retval() print a newline, just have the
caller always print the newline regardless if it calls print_graph_retval()
or not. This not only fixes this bug, but it also simplifies the code.
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Link: https://lore.kernel.org/20250411133015.015ca393@gandalf.local.home
Reported-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/ccc40f2b-4b9e-4abd-8daf-d22fce2a86f0@sirena.org.uk/
Fixes: ff5c9c576e754 ("ftrace: Add support for function argument to graph tracer")
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
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Hans Holmberg
Christoph Hellwig
Linus Torvalds
Artem Sadovnikov
Ojaswin Mujoo
Gustavo A. R. Silva
Tom Vierjahn
Nam Cao
Steven Rostedt