[PATCH] ext4: improve handling of conflincting mount options

[Theodore Ts'o <tytso@mit.edu>]

If the user explicitly specifies conflicting mount options for
delalloc or dioread_nolock and data=journal, fail the mount, instead
of printing a warning and continuing (since many user's won't look at
dmesg and notice the warning).

Also, print a single warning that data=journal implies that delayed
allocation is not on by default (since it's not supported), and
furthermore that O_DIRECT is not supported.  Improve the text in
Documentation/filesystems/ext4.txt so this is clear there as well.

Similarly, if the dioread_nolock mount option is specified when the
file system block size != PAGE_SIZE, fail the mount instead of
printing a warning message and ignoring the mount option.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---

n.b.  I plan to follow this up with a patch to the mount man page in
util-linux-ng

 Documentation/filesystems/ext4.txt |    8 ++++--
 fs/ext4/ext4.h                     |    3 ++
 fs/ext4/super.c                    |   46 +++++++++++++++++++++---------------
 3 files changed, 35 insertions(+), 22 deletions(-)

diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 232a575..168242b 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -160,7 +160,9 @@ noload			if the filesystem was not unmounted cleanly,
                      	lead to any number of problems.
 
 data=journal		All data are committed into the journal prior to being
-			written into the main file system.
+			written into the main file system.  Enabling
+			this mode will disable delayed allocation and
+			O_DIRECT support.
 
 data=ordered	(*)	All data are forced directly out to the main file
 			system prior to its metadata being committed to the
@@ -419,8 +421,8 @@ written to the journal first, and then to its final location.
 In the event of a crash, the journal can be replayed, bringing both data and
 metadata into a consistent state.  This mode is the slowest except when data
 needs to be read from and written to disk at the same time where it
-outperforms all others modes.  Currently ext4 does not have delayed
-allocation support if this data journalling mode is selected.
+outperforms all others modes.  Enabling this mode will disable delayed
+allocation and O_DIRECT support.
 
 /proc entries
 =============
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e717dfd..062c668 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -917,6 +917,9 @@ struct ext4_inode_info {
 #define EXT4_MOUNT_DISCARD		0x40000000 /* Issue DISCARD requests */
 #define EXT4_MOUNT_INIT_INODE_TABLE	0x80000000 /* Initialize uninitialized itables */
 
+#define EXT4_MOUNT2_EXPLICIT_DELALLOC	0x00000001 /* User explicitly
+						      specified delalloc */
+
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
 						~EXT4_MOUNT_##opt
 #define set_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt |= \
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 44d0c8d..c3e3a80 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1801,6 +1801,7 @@ set_qf_format:
 			break;
 		case Opt_nodelalloc:
 			clear_opt(sb, DELALLOC);
+			clear_opt2(sb, EXPLICIT_DELALLOC);
 			break;
 		case Opt_mblk_io_submit:
 			set_opt(sb, MBLK_IO_SUBMIT);
@@ -1817,6 +1818,7 @@ set_qf_format:
 			break;
 		case Opt_delalloc:
 			set_opt(sb, DELALLOC);
+			set_opt2(sb, EXPLICIT_DELALLOC);
 			break;
 		case Opt_block_validity:
 			set_opt(sb, BLOCK_VALIDITY);
@@ -3224,6 +3226,31 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
 			   &journal_ioprio, NULL, 0))
 		goto failed_mount;
 
+	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
+		printk_once(KERN_WARNING "EXT4-fs: Warning: mounting "
+			    "with data=journal disables delayed "
+			    "allocation and O_DIRECT support!\n");
+		if (test_opt2(sb, EXPLICIT_DELALLOC)) {
+			ext4_msg(sb, KERN_ERR, "can't mount with "
+				 "both data=journal and delalloc");
+			goto failed_mount;
+		}
+		if (test_opt(sb, DIOREAD_NOLOCK)) {
+			ext4_msg(sb, KERN_ERR, "can't mount with "
+				 "both data=journal and delalloc");
+			goto failed_mount;
+		}
+		if (test_opt(sb, DELALLOC))
+			clear_opt(sb, DELALLOC);
+	}
+	if (test_opt(sb, DIOREAD_NOLOCK)) {
+		if (sb->s_blocksize < PAGE_SIZE) {
+			ext4_msg(sb, KERN_ERR, "can't mount with "
+				 "dioread_nolock if block size != PAGE_SIZE");
+			goto failed_mount;
+		}
+	}
+
 	sb->s_flags = (sb->s_flags & ~MS_POSIXACL) |
 		(test_opt(sb, POSIX_ACL) ? MS_POSIXACL : 0);
 
@@ -3679,25 +3706,6 @@ no_journal:
 			 "available");
 	}
 
-	if (test_opt(sb, DELALLOC) &&
-	    (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)) {
-		ext4_msg(sb, KERN_WARNING, "Ignoring delalloc option - "
-			 "requested data journaling mode");
-		clear_opt(sb, DELALLOC);
-	}
-	if (test_opt(sb, DIOREAD_NOLOCK)) {
-		if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA) {
-			ext4_msg(sb, KERN_WARNING, "Ignoring dioread_nolock "
-				"option - requested data journaling mode");
-			clear_opt(sb, DIOREAD_NOLOCK);
-		}
-		if (sb->s_blocksize < PAGE_SIZE) {
-			ext4_msg(sb, KERN_WARNING, "Ignoring dioread_nolock "
-				"option - block size is too small");
-			clear_opt(sb, DIOREAD_NOLOCK);
-		}
-	}