[PATCH RFC 5/8] fs/ext4: Make DAX mount option a tri-state

ira.weiny
2020-04-14T04:01:53Z

From: Ira Weiny <ira.weiny@intel.com>

We add 'always', 'never', and 'inode' (default). '-o dax' continue to
operate the same.

Specifically we introduce a 2nd DAX mount flag EXT4_MOUNT_NODAX and set
it and EXT4_MOUNT_DAX appropriately.

We also force EXT4_MOUNT_NODAX if !CONFIG_FS_DAX.

https://lore.kernel.org/lkml/20200405061945.GA94792@iweiny-DESK2.sc.intel.com/

Signed-off-by: Ira Weiny <ira.weiny@intel.com>
---
fs/ext4/ext4.h | 1 +
fs/ext4/super.c | 43 +++++++++++++++++++++++++++++++++++++++----
2 files changed, 40 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 434021fcec88..aadf33d5b37d 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1174,6 +1174,7 @@ struct ext4_inode_info {
blocks */
#define EXT4_MOUNT2_HURD_COMPAT 0x00000004 /* Support HURD-castrated
file systems */
+#define EXT4_MOUNT2_NODAX 0x00000008 /* Do not allow Direct Access */

#define EXT4_MOUNT2_EXPLICIT_JOURNAL_CHECKSUM 0x00000008 /* User explicitly
specified journal checksum */
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index b14863058115..0175fbfeb2ea 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1510,6 +1510,7 @@ enum {
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_dax_str,
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,
@@ -1575,6 +1576,7 @@ static const match_table_t tokens = {
{Opt_barrier, "barrier"},
{Opt_nobarrier, "nobarrier"},
{Opt_i_version, "i_version"},
+ {Opt_dax_str, "dax=%s"},
{Opt_dax, "dax"},
{Opt_stripe, "stripe=%u"},
{Opt_delalloc, "delalloc"},
@@ -1772,6 +1774,7 @@ 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_str, 0, MOPT_STRING},
{Opt_dax, EXT4_MOUNT_DAX, MOPT_SET},
{Opt_stripe, 0, MOPT_GTE0},
{Opt_resuid, 0, MOPT_GTE0},
@@ -2081,13 +2084,32 @@ 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_str) {
#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;
+ char *tmp = match_strdup(&args[0]);
+
+ if (!tmp || !strcmp(tmp, "always")) {
+ ext4_msg(sb, KERN_WARNING,
+ "DAX enabled. Warning: EXPERIMENTAL, use at your own risk");
+ sbi->s_mount_opt |= EXT4_MOUNT_DAX;
+ sbi->s_mount_opt2 &= ~EXT4_MOUNT2_NODAX;
+ } else if (!strcmp(tmp, "never")) {
+ sbi->s_mount_opt2 |= EXT4_MOUNT2_NODAX;
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
+ } else if (!strcmp(tmp, "inode")) {
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
+ sbi->s_mount_opt2 &= ~EXT4_MOUNT2_NODAX;
+ } else {
+ ext4_msg(sb, KERN_WARNING, "DAX invalid option.");
+ kfree(tmp);
+ return -1;
+ }
+
+ kfree(tmp);
#else
ext4_msg(sb, KERN_INFO, "dax option not supported");
+ sbi->s_mount_opt2 |= EXT4_MOUNT2_NODAX;
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX;
return -1;
#endif
} else if (token == Opt_data_err_abort) {
@@ -2303,6 +2325,13 @@ 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_opt2(sb, NODAX))
+ SEQ_OPTS_PUTS("dax=never");
+ else if (test_opt(sb, DAX))
+ SEQ_OPTS_PUTS("dax=always");
+ else
+ SEQ_OPTS_PUTS("dax=inode");
+
ext4_show_quota_options(seq, sb);
return 0;
}
@@ -5424,6 +5453,12 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
sbi->s_mount_opt ^= EXT4_MOUNT_DAX;
}

+ if ((sbi->s_mount_opt2 ^ old_opts.s_mount_opt2) & EXT4_MOUNT2_NODAX) {
+ ext4_msg(sb, KERN_WARNING, "warning: refusing change of "
+ "non-dax flag with busy inodes while remounting");
+ sbi->s_mount_opt2 ^= EXT4_MOUNT2_NODAX;
+ }
+
if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
ext4_abort(sb, "Abort forced by user");

--
2.25.1