diff options
| author | Eric Biggers <ebiggers@google.com> | 2020-03-08 22:58:20 -0700 |
|---|---|---|
| committer | Steve French <stfrench@microsoft.com> | 2020-03-22 22:49:10 -0500 |
| commit | dc920277f1e59600c7cfd97438ee604ef6affdbd (patch) | |
| tree | e1ba4dd2475e90b7649bd42a6da257c01d2974e1 /fs/cifs | |
| parent | 266b9fecc58ca6b69a8852008896358830c0ba0f (diff) | |
cifs: clear PF_MEMALLOC before exiting demultiplex thread
Leaving PF_MEMALLOC set when exiting a kthread causes it to remain set
during do_exit(). That can confuse things. For example, if BSD process
accounting is enabled and the accounting file has FS_SYNC_FL set and is
located on an ext4 filesystem without a journal, then do_exit() can end
up calling ext4_write_inode(). That triggers the
WARN_ON_ONCE(current->flags & PF_MEMALLOC) there, as it assumes
(appropriately) that inodes aren't written when allocating memory.
This was originally reported for another kernel thread, xfsaild() [1].
cifs_demultiplex_thread() also exits with PF_MEMALLOC set, so it's
potentially subject to this same class of issue -- though I haven't been
able to reproduce the WARN_ON_ONCE() via CIFS, since unlike xfsaild(),
cifs_demultiplex_thread() is sent SIGKILL before exiting, and that
interrupts the write to the BSD process accounting file.
Either way, leaving PF_MEMALLOC set is potentially problematic. Let's
clean this up by properly saving and restoring PF_MEMALLOC.
[1] https://lore.kernel.org/r/0000000000000e7156059f751d7b@google.com
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cifs')
| -rw-r--r-- | fs/cifs/connect.c | 5 |
1 files changed, 4 insertions, 1 deletions
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c index 25262446b222..95b3ab0ca8c0 100644 --- a/fs/cifs/connect.c +++ b/fs/cifs/connect.c @@ -21,6 +21,7 @@ #include <linux/fs.h> #include <linux/net.h> #include <linux/string.h> +#include <linux/sched/mm.h> #include <linux/sched/signal.h> #include <linux/list.h> #include <linux/wait.h> @@ -1114,8 +1115,9 @@ cifs_demultiplex_thread(void *p) struct task_struct *task_to_wake = NULL; struct mid_q_entry *mids[MAX_COMPOUND]; char *bufs[MAX_COMPOUND]; + unsigned int noreclaim_flag; - current->flags |= PF_MEMALLOC; + noreclaim_flag = memalloc_noreclaim_save(); cifs_dbg(FYI, "Demultiplex PID: %d\n", task_pid_nr(current)); length = atomic_inc_return(&tcpSesAllocCount); @@ -1269,6 +1271,7 @@ next_pdu: set_current_state(TASK_RUNNING); } + memalloc_noreclaim_restore(noreclaim_flag); module_put_and_exit(0); } |