[PATCH] loop.c to use write ops for fs requiring special locking

[Robert S Peterson <rpeterso@redhat.com>]

Use normal write file operations rather than AOPS prepare_write and
commit_write when the backing filesystem requires special locking.

Signed-off-by:  Robert Peterson <rpeterso@redhat.com>

---

 drivers/block/loop.c |    9 ++++++++-
 include/linux/fs.h   |    1 +
 2 files changed, 9 insertions(+), 1 deletions(-)

121d2e76ae4b3f7ca3741e410664e138db5e1b13
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 9c3b94e..c762e76 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -44,6 +44,11 @@
  * backing filesystem.
  * Anton Altaparmakov, 16 Feb 2005
  *
+ * Extension of Anton's idea: Use normal write file operations rather than
+ * prepare_write and commit_write when the backing filesystem requires
+ * special locking.
+ * Robert Peterson <rpeterso@redhat.com>, 01 Mar 2006
+ *
  * Still To Fix:
  * - Advisory locking is ignored here.
  * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
@@ -74,6 +79,7 @@
 #include <linux/completion.h>
 #include <linux/highmem.h>
 #include <linux/gfp.h>
+#include <linux/mount.h>

 #include <asm/uaccess.h>

@@ -791,7 +797,8 @@ static int loop_set_fd(struct loop_devic
                 */
                if (!file->f_op->sendfile)
                        goto out_putf;
-               if (aops->prepare_write && aops->commit_write)
+               if (!(file->f_vfsmnt->mnt_sb->s_type->fs_flags & FS_AOPS_NEED_LOCKING) &&
+                       aops->prepare_write && aops->commit_write)
                        lo_flags |= LO_FLAGS_USE_AOPS;
                if (!(lo_flags & LO_FLAGS_USE_AOPS) && !file->f_op->write)
                        lo_flags |= LO_FLAGS_READ_ONLY;
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 9d96749..3def72e 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -88,6 +88,7 @@ extern int dir_notify_enable;
 /* public flags for file_system_type */
 #define FS_REQUIRES_DEV 1
 #define FS_BINARY_MOUNTDATA 2
+#define FS_AOPS_NEED_LOCKING 4 /* Filesystem aops have special locking needs */
 #define FS_REVAL_DOT   16384   /* Check the paths ".", ".." for staleness */
 #define FS_ODD_RENAME  32768   /* Temporary stuff; will go away as soon
                                  * as nfs_rename() will be cleaned up
--
1.2.4