Make direct_read_splice() limit the read to the end of the file for regular
files and block devices, thereby reducing the amount of allocation it will
do in such a case.
This means that the blockdev code doesn't require any special handling as
filemap_read_splice() also limits to i_size.
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Christoph Hellwig <hch@xxxxxx>
cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
cc: Jens Axboe <axboe@xxxxxxxxx>
cc: linux-block@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
cc: linux-mm@xxxxxxxxx
---
fs/splice.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/fs/splice.c b/fs/splice.c
index 4db3eee49423..89c8516554d1 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -315,6 +315,19 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos,
size_t used, npages, chunk, remain, keep = 0;
int i;
+ if (!len)
+ return 0;
+
+ if (S_ISREG(file_inode(in)->i_mode) ||
+ S_ISBLK(file_inode(in)->i_mode)) {
+ loff_t i_size = i_size_read(in->f_mapping->host);
+
+ if (*ppos >= i_size)
+ return 0;
+ if (len > i_size - *ppos)
+ len = i_size - *ppos;
+ }
+
/* Work out how much data we can actually add into the pipe */
used = pipe_occupancy(pipe->head, pipe->tail);
npages = max_t(ssize_t, pipe->max_usage - used, 0);
