dont-complain-about-incorrect-features-when-probing

   1 ext4: don't complain about incorrect features when probing
   2
   3 From: Eric Sandeen <sandeen@redhat.com>
   4
   5 If mount is auto-probing for filesystem type, it will try various
   6 filesystems in order, with the MS_SILENT flag set.  We get
   7 that flag as the silent arg to ext4_fill_super.
   8
   9 If we're probing (silent==1) then don't complain about feature
  10 incompatibilities that are found if it looks like it's actually
  11 a different valid extN type - failed probes should be silent
  12 in this case.
  13
  14 If the on-disk features are unknown even to ext4, then complain.
  15
  16 Reported-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
  17 Tested-by: Joakim Tjernlund <Joakim.Tjernlund@infinera.com>
  18 Signed-off-by: Eric Sandeen <sandeen@redhat.com>
  19 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
  20 Reviewed-by: Jan Kara <jack@suse.cz>
  21 ---
  22
  23 compile-tested only, sorry.
  24
  25 V2.  I lied.  (actually I hand-edited the patch in mail)  /Now/ it's compile tested,
  26 with the proper args to ext4_feature_set_ok :/
  27
  28 Having 2 gotos like this might not be preferable, but trying
  29 to write it more compactly led to what I thought was more
  30 difficult-to-read logic.
  31
  32
  33
  34
  35 diff --git a/fs/ext4/super.c b/fs/ext4/super.c
  36 index b0915b7..ae40368 100644
  37 --- a/fs/ext4/super.c
  38 +++ b/fs/ext4/super.c
  39 @@ -3659,6 +3659,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
  40                         ext4_msg(sb, KERN_INFO, "mounting ext2 file system "
  41                                  "using the ext4 subsystem");
  42                 else {
  43 +                       /*
  44 +                        * If we're probing be silent, if this looks like
  45 +                        * it's actually an ext[34] filesystem.
  46 +                        */
  47 +                       if (silent && ext4_feature_set_ok(sb, sb_rdonly(sb)))
  48 +                               goto failed_mount;
  49                         ext4_msg(sb, KERN_ERR, "couldn't mount as ext2 due "
  50                                  "to feature incompatibilities");
  51                         goto failed_mount;
  52 @@ -3670,6 +3676,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
  53                         ext4_msg(sb, KERN_INFO, "mounting ext3 file system "
  54                                  "using the ext4 subsystem");
  55                 else {
  56 +                       /*
  57 +                        * If we're probing be silent, if this looks like
  58 +                        * it's actually an ext4 filesystem.
  59 +                        */
  60 +                       if (silent && ext4_feature_set_ok(sb, sb_rdonly(sb)))
  61 +                               goto failed_mount;
  62                         ext4_msg(sb, KERN_ERR, "couldn't mount as ext3 due "
  63                                  "to feature incompatibilities");
  64                         goto failed_mount;
  65
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