[Devel] [PATCH RHEL7 COMMIT] ploop: io_direct must fsync after fallocate

[Konstantin Khorenko]

The commit is pushed to "branch-rh7-3.10.0-327.10.1.vz7.12.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-327.10.1.vz7.12.6
------>
commit 290460b9ae7a6add1de0ed4fcfba13ed0cbd9234
Author: Maxim Patlasov <mpatlasov at virtuozzo.com>
Date:   Fri Apr 8 13:14:59 2016 +0400

    ploop: io_direct must fsync after fallocate
    
    While handling fallocate(), ext4 firstly calls ext4_update_inode_size(),
    then ext4_mark_inode_dirty().  Both update only in-core state. After
    fallocate(), ploop updates BAT bypassing vfs layer (submit bio to
    underlying block device). Hence, it's possible that BAT is already
    updated, but i_size in now written to the disk yet. If a crash happens
    in the middle, BAT points beyond end-of-file, i.e. ploop image is
    corrupted.
    
    The patch fixes the problem by ordinary fsync(). This is OK because
    we fallocate relatively seldom (PLOOP_MAX_PREALLOC=128MB) and also
    because no dirty pages to sync (all I/O is direct).
    
    https://jira.sw.ru/browse/PSBM-45326
    
    Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
    Acked-by: Dmitry Monakhov <dmonakhov at virtuozzo.com>
---
 drivers/block/ploop/io_direct.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/block/ploop/io_direct.c b/drivers/block/ploop/io_direct.c
index 0c7e0c4..8032999 100644
--- a/drivers/block/ploop/io_direct.c
+++ b/drivers/block/ploop/io_direct.c
@@ -376,6 +376,7 @@ cached_submit(struct ploop_io *io, iblock_t iblk, struct ploop_request * preq,
 	loff_t new_size;
 	loff_t used_pos;
 	bool may_fallocate = io->files.file->f_op->fallocate &&
+		io->files.file->f_op->fsync &&
 		io->files.flags & EXT4_EXTENTS_FL;
 
 	trace_cached_submit(preq);
@@ -404,6 +405,11 @@ try_again:
 				}
 			}
 
+			/* flush new i_size to disk */
+			err = io->files.file->f_op->FOP_FSYNC(io->files.file, 0);
+			if (err)
+				goto end_write;
+
 			io->prealloced_size = prealloc;
 		}