tmpfs: support aio

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.)

Incorporate cleanups from Andrew Morton and Harvey Harrison.

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>
Cc: Christoph Rohland <hans-christoph.rohland@sap.com>
Cc: Badari Pulavarty <pbadari@us.ibm.com>
Cc: Zach Brown <zach.brown@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 34 insertions, 21 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index e2a6ae1a44e9..9ffbea9b79e1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1690,26 +1690,38 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_
         file_accessed(filp);
 }
 
-static ssize_t shmem_file_read(struct file *filp, char __user *buf, size_t count, loff_t *ppos)
-{
-        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;
+static ssize_t shmem_file_aio_read(struct kiocb *iocb,
+                const struct iovec *iov, unsigned long nr_segs, loff_t pos)
+{
+        struct file *filp = iocb->ki_filp;
+        ssize_t retval;
+        unsigned long seg;
+        size_t count;
+        loff_t *ppos = &iocb->ki_pos;
+
+        retval = generic_segment_checks(iov, &nr_segs, &count, VERIFY_WRITE);
+        if (retval)
+                return retval;
+
+        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 +2381,9 @@ static const struct file_operations shmem_file_operations = {
         .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,