UDF: Add support for O_DIRECT

Add support for the O_DIRECT flag.  There are two cases to deal with:

1. Small files stored in the ICB (inode control block?): just return 0
from the new udf_adinicb_direct_IO() handler to fall back to buffered
I/O.

2. Larger files, not stored in the ICB: nothing special here.  Just call
blockdev_direct_IO() from our new udf_direct_IO() handler and tidy up
any blocks instantiated outside i_size on error.  This is pretty
standard.  Factor error handling code out of udf_write_begin() into new
function udf_write_failed() so it can also be called by udf_direct_IO().

Also change the whitespace in udf_aops to make it a bit neater.

Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Signed-off-by: Jan Kara <jack@suse.cz>

2 files changed, 45 insertions, 16 deletions

diff --git a/fs/udf/file.c b/fs/udf/file.c
index d1c6093fd3d3..77b5953eaac8 100644
--- a/fs/udf/file.c
+++ b/fs/udf/file.c
@@ -118,11 +118,20 @@ static int udf_adinicb_write_end(struct file *file,
         return simple_write_end(file, mapping, pos, len, copied, page, fsdata);
 }
 
+static ssize_t udf_adinicb_direct_IO(int rw, struct kiocb *iocb,
+                                     const struct iovec *iov,
+                                     loff_t offset, unsigned long nr_segs)
+{
+        /* Fallback to buffered I/O. */
+        return 0;
+}
+
 const struct address_space_operations udf_adinicb_aops = {
         .readpage       = udf_adinicb_readpage,
         .writepage      = udf_adinicb_writepage,
         .write_begin    = udf_adinicb_write_begin,
         .write_end      = udf_adinicb_write_end,
+        .direct_IO      = udf_adinicb_direct_IO,
 };
 
 static ssize_t udf_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 1a0588e77a2f..41d58309d6a8 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -95,6 +95,22 @@ void udf_evict_inode(struct inode *inode)
         }
 }
 
+static void udf_write_failed(struct address_space *mapping, loff_t to)
+{
+        struct inode *inode = mapping->host;
+        struct udf_inode_info *iinfo = UDF_I(inode);
+        loff_t isize = inode->i_size;
+
+        if (to > isize) {
+                truncate_pagecache(inode, to, isize);
+                if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
+                        down_write(&iinfo->i_data_sem);
+                        udf_truncate_extents(inode);
+                        up_write(&iinfo->i_data_sem);
+                }
+        }
+}
+
 static int udf_writepage(struct page *page, struct writeback_control *wbc)
 {
         return block_write_full_page(page, udf_get_block, wbc);
@@ -124,21 +140,24 @@ static int udf_write_begin(struct file *file, struct address_space *mapping,
         int ret;
 
         ret = block_write_begin(mapping, pos, len, flags, pagep, udf_get_block);
-        if (unlikely(ret)) {
-                struct inode *inode = mapping->host;
-                struct udf_inode_info *iinfo = UDF_I(inode);
-                loff_t isize = inode->i_size;
-
-                if (pos + len > isize) {
-                        truncate_pagecache(inode, pos + len, isize);
-                        if (iinfo->i_alloc_type != ICBTAG_FLAG_AD_IN_ICB) {
-                                down_write(&iinfo->i_data_sem);
-                                udf_truncate_extents(inode);
-                                up_write(&iinfo->i_data_sem);
-                        }
-                }
-        }
+        if (unlikely(ret))
+                udf_write_failed(mapping, pos + len);
+        return ret;
+}
 
+static ssize_t udf_direct_IO(int rw, struct kiocb *iocb,
+                             const struct iovec *iov,
+                             loff_t offset, unsigned long nr_segs)
+{
+        struct file *file = iocb->ki_filp;
+        struct address_space *mapping = file->f_mapping;
+        struct inode *inode = mapping->host;
+        ssize_t ret;
+
+        ret = blockdev_direct_IO(rw, iocb, inode, iov, offset, nr_segs,
+                                  udf_get_block);
+        if (unlikely(ret < 0 && (rw & WRITE)))
+                udf_write_failed(mapping, offset + iov_length(iov, nr_segs));
         return ret;
 }
 
@@ -152,8 +171,9 @@ const struct address_space_operations udf_aops = {
         .readpages      = udf_readpages,
         .writepage      = udf_writepage,
         .writepages     = udf_writepages,
-        .write_begin            = udf_write_begin,
-        .write_end              = generic_write_end,
+        .write_begin    = udf_write_begin,
+        .write_end      = generic_write_end,
+        .direct_IO      = udf_direct_IO,
         .bmap           = udf_bmap,
 };