[PATCH V1 7/9] fs/ext4: Make DAX mount option a tri-state

ira.weiny
2020-05-14T06:53:51Z

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

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

We also force EXT4_MOUNT2_DAX_NEVER 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>

---
Changes from RFC:
Combine remount check for DAX_NEVER with DAX_ALWAYS
Update ext4_should_enable_dax()
---
fs/ext4/ext4.h | 1 +
fs/ext4/inode.c | 2 ++
fs/ext4/super.c | 43 +++++++++++++++++++++++++++++++++++++------
3 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 86a0994332ce..01d1de838896 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1168,6 +1168,7 @@ 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_EXPLICIT_JOURNAL_CHECKSUM 0x00000008 /* User explicitly
specified journal checksum */
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 23e42a223235..140b1930e2f4 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4400,6 +4400,8 @@ int ext4_get_inode_loc(struct inode *inode, struct ext4_iloc *iloc)

static bool ext4_should_enable_dax(struct inode *inode)
{
+ 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 5ec900fdf73c..e01a040a58a9 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1505,6 +1505,7 @@ 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,
@@ -1570,6 +1571,7 @@ 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"},
@@ -1767,6 +1769,7 @@ 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_ALWAYS, MOPT_SET},
{Opt_stripe, 0, MOPT_GTE0},
{Opt_resuid, 0, MOPT_GTE0},
@@ -2076,13 +2079,32 @@ 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_ALWAYS;
+ sbi->s_mount_opt2 &= ~EXT4_MOUNT2_DAX_NEVER;
+ } else if (!strcmp(tmp, "never")) {
+ sbi->s_mount_opt2 |= EXT4_MOUNT2_DAX_NEVER;
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
+ } else if (!strcmp(tmp, "inode")) {
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
+ sbi->s_mount_opt2 &= ~EXT4_MOUNT2_DAX_NEVER;
+ } 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_DAX_NEVER;
+ sbi->s_mount_opt &= ~EXT4_MOUNT_DAX_ALWAYS;
return -1;
#endif
} else if (token == Opt_data_err_abort) {
@@ -2306,6 +2328,13 @@ 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, DAX_NEVER))
+ SEQ_OPTS_PUTS("dax=never");
+ else if (test_opt(sb, DAX_ALWAYS))
+ SEQ_OPTS_PUTS("dax=always");
+ else
+ SEQ_OPTS_PUTS("dax=inode");
+
ext4_show_quota_options(seq, sb);
return 0;
}
@@ -5425,10 +5454,12 @@ 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) {
ext4_msg(sb, KERN_WARNING, "warning: refusing change of "
- "dax flag with busy inodes while remounting");
+ "dax mount option with busy inodes while remounting");
sbi->s_mount_opt ^= EXT4_MOUNT_DAX_ALWAYS;
+ sbi->s_mount_opt2 ^= EXT4_MOUNT2_DAX_NEVER;
}

if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED)
--
2.25.1