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Subject[PATCH V4 6/8] fs/ext4: Make DAX mount option a tri-state
Date
From: Ira Weiny <ira.weiny@intel.com>

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>

---
Changes from V1:
Fix up mounting options to only show an option if specified
Fix remount to prevent dax changes
Isolate behavior to ext4 only

Changes from RFC:
Combine remount check for DAX_NEVER with DAX_ALWAYS
Update ext4_should_enable_dax()
---
fs/ext4/ext4.h | 2 ++
fs/ext4/inode.c | 2 ++
fs/ext4/super.c | 67 +++++++++++++++++++++++++++++++++++++++++--------
3 files changed, 61 insertions(+), 10 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index f5291693ce6e..65ffb831b2b9 100644
--- 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 01636cf5f322..68fac9289109 100644
--- 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 80eb814c47eb..5e056aa20ce9 100644
--- 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)
--
2.25.1
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