ceph: fix short sync reads from the OSD

If we get a short read from the OSD because the object is small, we need to
zero the remainder of the buffer.  For O_DIRECT reads, the attempted range
is not trimmed to i_size by the VFS, so we were actually looping
indefinitely.

Fix by trimming by i_size, and the unconditionally zeroing the trailing
range.

Reported-by: Jeff Wu <cpwu@tnsoft.com.cn>
Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 15 insertions, 13 deletions

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 8c5ac4e72832..b654f403139e 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -283,7 +283,7 @@ int ceph_release(struct inode *inode, struct file *file)
 static int striped_read(struct inode *inode,
                         u64 off, u64 len,
                         struct page **pages, int num_pages,
-                        int *checkeof, bool align_to_pages,
+                        int *checkeof, bool o_direct,
                         unsigned long buf_align)
 {
         struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
@@ -308,7 +308,7 @@ static int striped_read(struct inode *inode,
         io_align = off & ~PAGE_MASK;
 
 more:
-        if (align_to_pages)
+        if (o_direct)
                 page_align = (pos - io_align + buf_align) & ~PAGE_MASK;
         else
                 page_align = pos & ~PAGE_MASK;
@@ -346,20 +346,22 @@ more:
         }
 
         if (was_short) {
-                /* was original extent fully inside i_size? */
-                if (pos + left <= inode->i_size) {
-                        dout("zero tail\n");
-                        ceph_zero_page_vector_range(page_off + read, len - read,
+                /* did we bounce off eof? */
+                if (pos + left > inode->i_size)
+                        *checkeof = 1;
+
+                /* zero trailing bytes (inside i_size) */
+                if (left > 0 && pos < inode->i_size) {
+                        if (pos + left > inode->i_size)
+                                left = inode->i_size - pos;
+
+                        dout("zero tail %d\n", left);
+                        ceph_zero_page_vector_range(page_off + read, left,
                                                     pages);
-                        read = len;
-                        goto out;
+                        read += left;
                 }
-
-                /* check i_size */
-                *checkeof = 1;
         }
 
-out:
         if (ret >= 0)
                 ret = read;
         dout("striped_read returns %d\n", ret);
@@ -659,7 +661,7 @@ out:
 
                 /* hit EOF or hole? */
                 if (statret == 0 && *ppos < inode->i_size) {
-                        dout("aio_read sync_read hit hole, reading more\n");
+                        dout("aio_read sync_read hit hole, ppos %lld < size %lld, reading more\n", *ppos, inode->i_size);
                         read += ret;
                         base += ret;
                         len -= ret;