gfs2: Fix freeze consistency check in log_write_header

Functions gfs2_freeze_super() and gfs2_thaw_super() are using the
SDF_FROZEN flag to indicate when the filesystem is frozen, synchronized
by sd_freeze_mutex.  However, this doesn't prevent writes from happening
between the point of calling thaw_super() and the point where the
SDF_FROZEN flag is cleared, so the following assert can trigger in
log_write_header():

    gfs2_assert_withdraw(sdp, !test_bit(SDF_FROZEN, &sdp->sd_flags));

Fix that by checking for sb->s_writers.frozen != SB_FREEZE_COMPLETE in
log_write_header() instead.  To make sure that the filesystem-specific
part of freezing happens before sb->s_writers.frozen is set to
SB_FREEZE_COMPLETE, move that code from gfs2_freeze_locally() into
gfs2_freeze_fs() and hook that up to the .freeze_fs operation.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 6b3ba8f7b67a936a0344e2fba27be079f68fbb52..8cddf955ebc0cca9d4de9e7577f081d8b947ac81 100644 (file)
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -913,8 +913,9 @@ void gfs2_write_log_header(struct gfs2_sbd *sdp, struct gfs2_jdesc *jd,
 static void log_write_header(struct gfs2_sbd *sdp, u32 flags)
 {
        blk_opf_t op_flags = REQ_PREFLUSH | REQ_FUA | REQ_META | REQ_SYNC;
+       struct super_block *sb = sdp->sd_vfs;
 
-       gfs2_assert_withdraw(sdp, !test_bit(SDF_FROZEN, &sdp->sd_flags));
+       gfs2_assert_withdraw(sdp, sb->s_writers.frozen != SB_FREEZE_COMPLETE);
 
        if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags)) {
                gfs2_ordered_wait(sdp);

diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index ae92ae1203d8fba772a070694f3467b9133f5877..e5f79466340d2aa3d5eb76262e0c04b1d8cfd9d5 100644 (file)
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -673,28 +673,6 @@ static int gfs2_sync_fs(struct super_block *sb, int wait)
        return sdp->sd_log_error;
 }
 
-static int gfs2_freeze_locally(struct gfs2_sbd *sdp)
-{
-       struct super_block *sb = sdp->sd_vfs;
-       int error;
-
-       error = freeze_super(sb, FREEZE_HOLDER_USERSPACE);
-       if (error)
-               return error;
-
-       if (test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags)) {
-               gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_FREEZE |
-                              GFS2_LFC_FREEZE_GO_SYNC);
-               if (gfs2_withdrawing_or_withdrawn(sdp)) {
-                       error = thaw_super(sb, FREEZE_HOLDER_USERSPACE);
-                       if (error)
-                               return error;
-                       return -EIO;
-               }
-       }
-       return 0;
-}
-
 static int gfs2_do_thaw(struct gfs2_sbd *sdp)
 {
        struct super_block *sb = sdp->sd_vfs;
@@ -724,7 +702,7 @@ void gfs2_freeze_func(struct work_struct *work)
        if (test_bit(SDF_FROZEN, &sdp->sd_flags))
                goto freeze_failed;
 
-       error = gfs2_freeze_locally(sdp);
+       error = freeze_super(sb, FREEZE_HOLDER_USERSPACE);
        if (error)
                goto freeze_failed;
 
@@ -765,7 +743,7 @@ static int gfs2_freeze_super(struct super_block *sb, enum freeze_holder who)
        }
 
        for (;;) {
-               error = gfs2_freeze_locally(sdp);
+               error = freeze_super(sb, FREEZE_HOLDER_USERSPACE);
                if (error) {
                        fs_info(sdp, "GFS2: couldn't freeze filesystem: %d\n",
                                error);
@@ -801,6 +779,19 @@ out:
        return error;
 }
 
+static int gfs2_freeze_fs(struct super_block *sb)
+{
+       struct gfs2_sbd *sdp = sb->s_fs_info;
+
+       if (test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags)) {
+               gfs2_log_flush(sdp, NULL, GFS2_LOG_HEAD_FLUSH_FREEZE |
+                              GFS2_LFC_FREEZE_GO_SYNC);
+               if (gfs2_withdrawing_or_withdrawn(sdp))
+                       return -EIO;
+       }
+       return 0;
+}
+
 /**
  * gfs2_thaw_super - reallow writes to the filesystem
  * @sb: the VFS structure for the filesystem
@@ -1599,6 +1590,7 @@ const struct super_operations gfs2_super_ops = {
        .put_super              = gfs2_put_super,
        .sync_fs                = gfs2_sync_fs,
        .freeze_super           = gfs2_freeze_super,
+       .freeze_fs              = gfs2_freeze_fs,
        .thaw_super             = gfs2_thaw_super,
        .statfs                 = gfs2_statfs,
        .drop_inode             = gfs2_drop_inode,