iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

tmpfs: don't interrupt fallocate with EINTR

Browse Source 
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@redhat.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20240515221044.590-1-jack@suse.cz
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Mikulas Patocka 2024-05-16 00:10:44 +02:00 committed by Christian Brauner
parent 2a010c4128
commit ca86a5d2f9
1 changed files with 6 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
mm/shmem.c
View File

@ -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;