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authorSachin Prabhu <sprabhu@redhat.com>2014-03-11 16:11:47 +0000
committerSteve French <smfrench@gmail.com>2014-04-16 13:51:46 -0500
commitc11f1df5003d534fd067f0168bfad7befffb3b5c (patch)
tree048afe1d692c6ab1e446334930c3c116a161978e /fs/cifs/smb2ops.c
parent0f689a33ad17845363acdc6d52783befd6ad116c (diff)
cifs: Wait for writebacks to complete before attempting write.
Problem reported in Red Hat bz 1040329 for strict writes where we cache only when we hold oplock and write direct to the server when we don't. When we receive an oplock break, we first change the oplock value for the inode in cifsInodeInfo->oplock to indicate that we no longer hold the oplock before we enqueue a task to flush changes to the backing device. Once we have completed flushing the changes, we return the oplock to the server. There are 2 ways here where we can have data corruption 1) While we flush changes to the backing device as part of the oplock break, we can have processes write to the file. These writes check for the oplock, find none and attempt to write directly to the server. These direct writes made while we are flushing from cache could be overwritten by data being flushed from the cache causing data corruption. 2) While a thread runs in cifs_strict_writev, the machine could receive and process an oplock break after the thread has checked the oplock and found that it allows us to cache and before we have made changes to the cache. In that case, we end up with a dirty page in cache when we shouldn't have any. This will be flushed later and will overwrite all subsequent writes to the part of the file represented by this page. Before making any writes to the server, we need to confirm that we are not in the process of flushing data to the server and if we are, we should wait until the process is complete before we attempt the write. We should also wait for existing writes to complete before we process an oplock break request which changes oplock values. We add a version specific downgrade_oplock() operation to allow for differences in the oplock values set for the different smb versions. Cc: stable@vger.kernel.org Signed-off-by: Sachin Prabhu <sprabhu@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> Reviewed-by: Pavel Shilovsky <piastry@etersoft.ru> Signed-off-by: Steve French <smfrench@gmail.com>
Diffstat (limited to 'fs/cifs/smb2ops.c')
-rw-r--r--fs/cifs/smb2ops.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/fs/cifs/smb2ops.c b/fs/cifs/smb2ops.c
index 192f51a12cf1..35ddc3ed119d 100644
--- a/fs/cifs/smb2ops.c
+++ b/fs/cifs/smb2ops.c
@@ -905,6 +905,17 @@ smb2_query_symlink(const unsigned int xid, struct cifs_tcon *tcon,
}
static void
+smb2_downgrade_oplock(struct TCP_Server_Info *server,
+ struct cifsInodeInfo *cinode, bool set_level2)
+{
+ if (set_level2)
+ server->ops->set_oplock_level(cinode, SMB2_OPLOCK_LEVEL_II,
+ 0, NULL);
+ else
+ server->ops->set_oplock_level(cinode, 0, 0, NULL);
+}
+
+static void
smb2_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock,
unsigned int epoch, bool *purge_cache)
{
@@ -1110,6 +1121,7 @@ struct smb_version_operations smb20_operations = {
.clear_stats = smb2_clear_stats,
.print_stats = smb2_print_stats,
.is_oplock_break = smb2_is_valid_oplock_break,
+ .downgrade_oplock = smb2_downgrade_oplock,
.need_neg = smb2_need_neg,
.negotiate = smb2_negotiate,
.negotiate_wsize = smb2_negotiate_wsize,
@@ -1184,6 +1196,7 @@ struct smb_version_operations smb21_operations = {
.clear_stats = smb2_clear_stats,
.print_stats = smb2_print_stats,
.is_oplock_break = smb2_is_valid_oplock_break,
+ .downgrade_oplock = smb2_downgrade_oplock,
.need_neg = smb2_need_neg,
.negotiate = smb2_negotiate,
.negotiate_wsize = smb2_negotiate_wsize,
@@ -1259,6 +1272,7 @@ struct smb_version_operations smb30_operations = {
.print_stats = smb2_print_stats,
.dump_share_caps = smb2_dump_share_caps,
.is_oplock_break = smb2_is_valid_oplock_break,
+ .downgrade_oplock = smb2_downgrade_oplock,
.need_neg = smb2_need_neg,
.negotiate = smb2_negotiate,
.negotiate_wsize = smb2_negotiate_wsize,