fs/ext4: Make DAX mount option a tri-state

We add 'always', 'never', and 'inode' (default).  '-o dax' continues to
operate the same which is equivalent to 'always'.  This new
functionality is limited to ext4 only.

Specifically we introduce a 2nd DAX mount flag EXT4_MOUNT2_DAX_NEVER and set
it and EXT4_MOUNT_DAX_ALWAYS appropriately for the mode.

We also force EXT4_MOUNT2_DAX_NEVER if !CONFIG_FS_DAX.

Finally, EXT4_MOUNT2_DAX_INODE is used solely to detect if the user
specified that option for printing.

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20200528150003.828793-7-ira.weiny@intel.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f529169..65ffb83 100644 (file)
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1168,6 +1168,8 @@ struct ext4_inode_info {
                                                      blocks */
 #define EXT4_MOUNT2_HURD_COMPAT                0x00000004 /* Support HURD-castrated
                                                      file systems */
+#define EXT4_MOUNT2_DAX_NEVER          0x00000008 /* Do not allow Direct Access */
+#define EXT4_MOUNT2_DAX_INODE          0x00000010 /* For printing options only */
 
 #define EXT4_MOUNT2_EXPLICIT_JOURNAL_CHECKSUM  0x00000008 /* User explicitly
                                                specified journal checksum */

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 01636cf..68fac92 100644 (file)
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4402,6 +4402,8 @@ static bool ext4_should_enable_dax(struct inode *inode)
 {
        struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
 
+       if (test_opt2(inode->i_sb, DAX_NEVER))
+               return false;
        if (!S_ISREG(inode->i_mode))
                return false;
        if (ext4_should_journal_data(inode))

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 80eb814..5e056aa 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1512,7 +1512,8 @@ enum {
        Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
        Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
        Opt_noquota, Opt_barrier, Opt_nobarrier, Opt_err,
-       Opt_usrquota, Opt_grpquota, Opt_prjquota, Opt_i_version, Opt_dax,
+       Opt_usrquota, Opt_grpquota, Opt_prjquota, Opt_i_version,
+       Opt_dax, Opt_dax_always, Opt_dax_inode, Opt_dax_never,
        Opt_stripe, Opt_delalloc, Opt_nodelalloc, Opt_warn_on_error,
        Opt_nowarn_on_error, Opt_mblk_io_submit,
        Opt_lazytime, Opt_nolazytime, Opt_debug_want_extra_isize,
@@ -1579,6 +1580,9 @@ static const match_table_t tokens = {
        {Opt_nobarrier, "nobarrier"},
        {Opt_i_version, "i_version"},
        {Opt_dax, "dax"},
+       {Opt_dax_always, "dax=always"},
+       {Opt_dax_inode, "dax=inode"},
+       {Opt_dax_never, "dax=never"},
        {Opt_stripe, "stripe=%u"},
        {Opt_delalloc, "delalloc"},
        {Opt_warn_on_error, "warn_on_error"},
@@ -1726,6 +1730,7 @@ static int clear_qf_name(struct super_block *sb, int qtype)
 #define MOPT_NO_EXT3   0x0200
 #define MOPT_EXT4_ONLY (MOPT_NO_EXT2 | MOPT_NO_EXT3)
 #define MOPT_STRING    0x0400
+#define MOPT_SKIP      0x0800
 
 static const struct mount_opts {
        int     token;
@@ -1775,7 +1780,13 @@ static const struct mount_opts {
        {Opt_min_batch_time, 0, MOPT_GTE0},
        {Opt_inode_readahead_blks, 0, MOPT_GTE0},
        {Opt_init_itable, 0, MOPT_GTE0},
-       {Opt_dax, EXT4_MOUNT_DAX_ALWAYS, MOPT_SET},
+       {Opt_dax, EXT4_MOUNT_DAX_ALWAYS, MOPT_SET | MOPT_SKIP},
+       {Opt_dax_always, EXT4_MOUNT_DAX_ALWAYS,
+               MOPT_EXT4_ONLY | MOPT_SET | MOPT_SKIP},
+       {Opt_dax_inode, EXT4_MOUNT2_DAX_INODE,
+               MOPT_EXT4_ONLY | MOPT_SET | MOPT_SKIP},
+       {Opt_dax_never, EXT4_MOUNT2_DAX_NEVER,
+               MOPT_EXT4_ONLY | MOPT_SET | MOPT_SKIP},
        {Opt_stripe, 0, MOPT_GTE0},
        {Opt_resuid, 0, MOPT_GTE0},
        {Opt_resgid, 0, MOPT_GTE0},
@@ -2084,13 +2095,32 @@ static int handle_mount_opt(struct super_block *sb, char *opt, int token,
                }
                sbi->s_jquota_fmt = m->mount_opt;
 #endif
-       } else if (token == Opt_dax) {
+       } else if (token == Opt_dax || token == Opt_dax_always ||
+                  token == Opt_dax_inode || token == Opt_dax_never) {
 #ifdef CONFIG_FS_DAX
-               ext4_msg(sb, KERN_WARNING,
-               "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
-               sbi->s_mount_opt |= m->mount_opt;
+               switch (token) {
+               case Opt_dax:
+               case Opt_dax_always:
+                       ext4_msg(sb, KERN_WARNING,
+                               "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+                       sbi->s_mount_opt |= EXT4_MOUNT_DAX_ALWAYS;
+                       sbi->s_mount_opt2 &= ~EXT4_MOUNT2_DAX_NEVER;
+                       break;
+               case Opt_dax_never:
+                       sbi->s_mount_opt2 |= EXT4_MOUNT2_DAX_NEVER;
+                       sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
+                       break;
+               case Opt_dax_inode:
+                       sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
+                       sbi->s_mount_opt2 &= ~EXT4_MOUNT2_DAX_NEVER;
+                       /* Strictly for printing options */
+                       sbi->s_mount_opt2 |= EXT4_MOUNT2_DAX_INODE;
+                       break;
+               }
 #else
                ext4_msg(sb, KERN_INFO, "dax option not supported");
+               sbi->s_mount_opt2 |= EXT4_MOUNT2_DAX_NEVER;
+               sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
                return -1;
 #endif
        } else if (token == Opt_data_err_abort) {
@@ -2254,7 +2284,7 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
        for (m = ext4_mount_opts; m->token != Opt_err; m++) {
                int want_set = m->flags & MOPT_SET;
                if (((m->flags & (MOPT_SET|MOPT_CLEAR)) == 0) ||
-                   (m->flags & MOPT_CLEAR_ERR))
+                   (m->flags & MOPT_CLEAR_ERR) || m->flags & MOPT_SKIP)
                        continue;
                if (!nodefs && !(m->mount_opt & (sbi->s_mount_opt ^ def_mount_opt)))
                        continue; /* skip if same as the default */
@@ -2314,6 +2344,17 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
        if (DUMMY_ENCRYPTION_ENABLED(sbi))
                SEQ_OPTS_PUTS("test_dummy_encryption");
 
+       if (test_opt(sb, DAX_ALWAYS)) {
+               if (IS_EXT2_SB(sb))
+                       SEQ_OPTS_PUTS("dax");
+               else
+                       SEQ_OPTS_PUTS("dax=always");
+       } else if (test_opt2(sb, DAX_NEVER)) {
+               SEQ_OPTS_PUTS("dax=never");
+       } else if (test_opt2(sb, DAX_INODE)) {
+               SEQ_OPTS_PUTS("dax=inode");
+       }
+
        ext4_show_quota_options(seq, sb);
        return 0;
 }
@@ -5436,10 +5477,16 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
                goto restore_opts;
        }
 
-       if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_DAX_ALWAYS) {
+       if ((sbi->s_mount_opt ^ old_opts.s_mount_opt) & EXT4_MOUNT_DAX_ALWAYS ||
+           (sbi->s_mount_opt2 ^ old_opts.s_mount_opt2) & EXT4_MOUNT2_DAX_NEVER ||
+           (sbi->s_mount_opt2 ^ old_opts.s_mount_opt2) & EXT4_MOUNT2_DAX_INODE) {
                ext4_msg(sb, KERN_WARNING, "warning: refusing change of "
-                       "dax flag with busy inodes while remounting");
-               sbi->s_mount_opt ^= EXT4_MOUNT_DAX_ALWAYS;
+                       "dax mount option with busy inodes while remounting");
+               sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
+               sbi->s_mount_opt |= old_opts.s_mount_opt & EXT4_MOUNT_DAX_ALWAYS;
+               sbi->s_mount_opt2 &= ~(EXT4_MOUNT2_DAX_NEVER | EXT4_MOUNT2_DAX_INODE);
+               sbi->s_mount_opt2 |= old_opts.s_mount_opt2 &
+                                    (EXT4_MOUNT2_DAX_NEVER | EXT4_MOUNT2_DAX_INODE);
        }
 
        if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)