We have a request for tmpfs to support the AIO interface: easily done,
no more than replacing the old shmem_file_read by shmem_file_aio_read,
cribbed from generic_file_aio_read. (In 2.6.25 its write side was
already changed to use generic_file_aio_write.)
Tests out fine with LTP's ltp-aiodio.sh, given hacks (not included)
to support O_DIRECT. tmpfs cannot honestly support O_DIRECT: its
cache-avoiding-IO nature is at odds with direct IO-avoiding-cache.
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Tested-by: Lawrence Greenfield <leg@google.com>
---
mm/shmem.c | 57 +++++++++++++++++++++++++++++++++------------------
1 file changed, 37 insertions(+), 20 deletions(-)
--- 2.6.26-rc4/mm/shmem.c 2008-05-03 21:55:12.000000000 +0100
+++ linux/mm/shmem.c 2008-05-28 23:51:24.000000000 +0100
@@ -1690,26 +1690,42 @@ static void do_shmem_file_read(struct fi
file_accessed(filp);
}
-static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
+static ssize_t shmem_file_aio_read(struct kiocb *iocb,
+ const struct iovec *iov, unsigned long nr_segs, loff_t pos)
{
- read_descriptor_t desc;
-
- if ((ssize_t) count < 0)
- return -EINVAL;
- if (!access_ok(VERIFY_WRITE, buf, count))
- return -EFAULT;
- if (!count)
- return 0;
-
- desc.written = 0;
- desc.count = count;
- desc.arg.buf = buf;
- desc.error = 0;
-
- do_shmem_file_read(filp, ppos, &desc, file_read_actor);
- if (desc.written)
- return desc.written;
- return desc.error;
+ struct file *filp = iocb->ki_filp;
+ ssize_t retval;
+ unsigned long seg;
+ size_t count;
+ loff_t *ppos = &iocb->ki_pos;
+
+ count = 0;
+ retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
+ if (retval)
+ return retval;
+
+ retval = 0;
+ if (count) {
+ for (seg = 0; seg < nr_segs; seg++) {
+ read_descriptor_t desc;
+
+ desc.written = 0;
+ desc.arg.buf = iov[seg].iov_base;
+ desc.count = iov[seg].iov_len;
+ if (desc.count == 0)
+ continue;
+ desc.error = 0;
+ do_shmem_file_read(filp, ppos, &desc, file_read_actor);
+ retval += desc.written;
+ if (desc.error) {
+ retval = retval ?: desc.error;
+ break;
+ }
+ if (desc.count > 0)
+ break;
+ }
+ }
+ return retval;
}
static int shmem_statfs(struct dentry *dentry, struct kstatfs *buf)
@@ -2369,8 +2385,9 @@ static const struct file_operations shme
.mmap = shmem_mmap,
#ifdef CONFIG_TMPFS
.llseek = generic_file_llseek,
- .read = shmem_file_read,
+ .read = do_sync_read,
.write = do_sync_write,
+ .aio_read = shmem_file_aio_read,
.aio_write = generic_file_aio_write,
.fsync = simple_sync_file,
.splice_read = generic_file_splice_read,
--
