ext4: improve handling of conflicting mount options

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>

2 files changed, 32 insertions, 21 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ccfa81f33bb0..48ae98819d35 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -922,6 +922,9 @@ 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 44d0c8db2239..ee2f74a7084d 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 +3226,33 @@ 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);
+        }
+
+        blocksize = BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
+        if (test_opt(sb, DIOREAD_NOLOCK)) {
+                if (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);
 
@@ -3265,8 +3294,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
         if (!ext4_feature_set_ok(sb, (sb->s_flags & MS_RDONLY)))
                 goto failed_mount;
 
-        blocksize = BLOCK_SIZE << le32_to_cpu(es->s_log_block_size);
-
         if (blocksize < EXT4_MIN_BLOCK_SIZE ||
             blocksize > EXT4_MAX_BLOCK_SIZE) {
                 ext4_msg(sb, KERN_ERR,
@@ -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);
-                }
-        }
-
         err = ext4_setup_system_zone(sb);
         if (err) {
                 ext4_msg(sb, KERN_ERR, "failed to initialize system "