From: Mikulas Patocka <mpatocka@xxxxxxxxxx> I have a program that sets up a periodic timer with 10ms interval. When the program attempts to call fallocate(2) on tmpfs, it goes into an infinite loop. fallocate(2) takes longer than 10ms, so it gets interrupted by a signal and it returns EINTR. On EINTR, the fallocate call is restarted, going into the same loop again. Let's change the signal_pending() check in shmem_fallocate() loop to fatal_signal_pending(). This solves the problem of shmem_fallocate() constantly restarting. Since most other filesystem's fallocate methods don't react to signals, it is unlikely userspace really relies on timely delivery of non-fatal signals while fallocate is running. Also the comment before the signal check: /* * Good, the fallocate(2) manpage permits EINTR: we may have * been interrupted because we are using up too much memory. */ indicates that the check was mainly added for OOM situations in which case the process will be sent a fatal signal so this change preserves the behavior in OOM situations. [JK: Update changelog and comment based on upstream discussion] Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> Signed-off-by: Jan Kara <jack@xxxxxxx> --- mm/shmem.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 1f84a41aeb85..9c148f9723f4 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3167,10 +3167,13 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset, struct folio *folio; /* - * Good, the fallocate(2) manpage permits EINTR: we may have - * been interrupted because we are using up too much memory. + * Check for fatal signal so that we abort early in OOM + * situations. We don't want to abort in case of non-fatal + * signals as large fallocate can take noticeable time and + * e.g. periodic timers may result in fallocate constantly + * restarting. */ - if (signal_pending(current)) + if (fatal_signal_pending(current)) error = -EINTR; else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced) error = -ENOMEM; -- 2.35.3
