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| author |   Pavel Begunkov <asml.silence@gmail.com> | 2021-09-08 20:10:38 +0100 |
|---|---|---|
| committer |   Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-09-14 10:46:19 +0200 |
| commit | e5f71d60ff167d0caa491659d65551a55ea6b406 (patch) | |
| tree | 3a6f7e0b1524aa1e77b4134b12104472a12aa4f1 /drivers/char/mem.c | |
| parent | Linux 5.15-rc1 (diff) | |
| download | linux-dev-e5f71d60ff167d0caa491659d65551a55ea6b406.tar.xz linux-dev-e5f71d60ff167d0caa491659d65551a55ea6b406.zip | |
/dev/mem: nowait zero/null ops
Make read_iter_zero() to honor IOCB_NOWAIT, so /dev/zero can be
advertised as FMODE_NOWAIT. It's useful for io_uring, which needs it to
apply certain optimisations when doing I/O against the device.
Set FMODE_NOWAIT for /dev/null as well, it never waits and therefore
trivially meets the criteria.
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f11090f97ddc2b2ce49ea1211258658ddfbc5563.1631127867.git.asml.silence@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/char/mem.c')
| -rw-r--r-- | drivers/char/mem.c | 8 |
1 files changed, 6 insertions, 2 deletions
diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1c596b5cdb27..cc296f0823bd 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -495,6 +495,10 @@ static ssize_t read_iter_zero(struct kiocb *iocb, struct iov_iter *iter) written += n; if (signal_pending(current)) return written ? written : -ERESTARTSYS; + if (!need_resched()) + continue; + if (iocb->ki_flags & IOCB_NOWAIT) + return written ? written : -EAGAIN; cond_resched(); } return written; @@ -696,11 +700,11 @@ static const struct memdev { #ifdef CONFIG_DEVMEM [DEVMEM_MINOR] = { "mem", 0, &mem_fops, FMODE_UNSIGNED_OFFSET }, #endif - [3] = { "null", 0666, &null_fops, 0 }, + [3] = { "null", 0666, &null_fops, FMODE_NOWAIT }, #ifdef CONFIG_DEVPORT [4] = { "port", 0, &port_fops, 0 }, #endif - [5] = { "zero", 0666, &zero_fops, 0 }, + [5] = { "zero", 0666, &zero_fops, FMODE_NOWAIT }, [7] = { "full", 0666, &full_fops, 0 }, [8] = { "random", 0666, &random_fops, 0 }, [9] = { "urandom", 0666, &urandom_fops, 0 }, |