From ca86a5d2f9feed16e11023891c8c70aa57ced24e Mon Sep 17 00:00:00 2001 From: Mikulas Patocka Date: Thu, 16 May 2024 00:10:44 +0200 Subject: tmpfs: don't interrupt fallocate with EINTR 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 Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20240515221044.590-1-jack@suse.cz Reviewed-by: Matthew Wilcox (Oracle) Signed-off-by: Christian Brauner --- mm/shmem.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index f5d60436b604..ff7c756a7d02 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3166,10 +3166,13 @@ 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; -- cgit v1.2.3