From 1b057bd800c3ea0c926191d7950cd2365eddc9bb Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Tue, 19 Sep 2023 09:37:42 +0200 Subject: drivers/char/mem: implement splice() for /dev/zero, /dev/full This allows splicing zeroed pages into a pipe, and allows discarding pages from a pipe by splicing them to /dev/zero. Writing to /dev/zero should have the same effect as writing to /dev/null, and a "splice_write" implementation exists only for /dev/null. (The /dev/zero splice_read implementation could be optimized by pushing references to the global zero page to the pipe, but that's an optimization for another day.) Signed-off-by: Max Kellermann Link: https://lore.kernel.org/r/20230919073743.1066313-1-max.kellermann@ionos.com Signed-off-by: Greg Kroah-Hartman --- drivers/char/mem.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'drivers/char/mem.c') diff --git a/drivers/char/mem.c b/drivers/char/mem.c index 1052b0f2d4cf..263c19cd6fb9 100644 --- a/drivers/char/mem.c +++ b/drivers/char/mem.c @@ -640,6 +640,7 @@ static int open_port(struct inode *inode, struct file *filp) #define full_lseek null_lseek #define write_zero write_null #define write_iter_zero write_iter_null +#define splice_write_zero splice_write_null #define open_mem open_port static const struct file_operations __maybe_unused mem_fops = { @@ -677,6 +678,8 @@ static const struct file_operations zero_fops = { .read_iter = read_iter_zero, .read = read_zero, .write_iter = write_iter_zero, + .splice_read = copy_splice_read, + .splice_write = splice_write_zero, .mmap = mmap_zero, .get_unmapped_area = get_unmapped_area_zero, #ifndef CONFIG_MMU @@ -688,6 +691,7 @@ static const struct file_operations full_fops = { .llseek = full_lseek, .read_iter = read_iter_zero, .write = write_full, + .splice_read = copy_splice_read, }; static const struct memdev { -- cgit v1.2.3