[PATCH RFC 7/8] ext4: Add mount option for provisioning blocks during allocations

[Sarthak Kukreti <sarthakkukreti@chromium.org>]

From: Sarthak Kukreti <sarthakkukreti@chromium.org>

Add a mount option that sets the default provisioning mode for
all files within the filesystem.

Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
---
 fs/ext4/ext4.h    | 1 +
 fs/ext4/extents.c | 7 +++++++
 fs/ext4/super.c   | 7 +++++++
 3 files changed, 15 insertions(+)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index ec0871e687c1..75f6e7f2f90b 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1271,6 +1271,7 @@ struct ext4_inode_info {
 #define EXT4_MOUNT2_MB_OPTIMIZE_SCAN	0x00000080 /* Optimize group
 						    * scanning in mballoc
 						    */
+#define EXT4_MOUNT2_PROVISION		0x00000100 /* Provision while allocating file blocks */
 
 #define clear_opt(sb, opt)		EXT4_SB(sb)->s_mount_opt &= \
 						~EXT4_MOUNT_##opt
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 7a096144b7f8..746213b5ec3d 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4437,6 +4437,13 @@ static int ext4_alloc_file_blocks(struct file *file, ext4_lblk_t offset,
 	unsigned int credits;
 	loff_t epos;
 
+	/*
+	 * Attempt to provision file blocks if the mount is mounted with
+	 * provision.
+	 */
+	if (test_opt2(inode->i_sb, PROVISION))
+		flags |= EXT4_GET_BLOCKS_PROVISION;
+
 	BUG_ON(!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS));
 	map.m_lblk = offset;
 	map.m_len = len;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 9a66abcca1a8..5ece1868f332 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1596,6 +1596,7 @@ enum {
 	Opt_max_dir_size_kb, Opt_nojournal_checksum, Opt_nombcache,
 	Opt_no_prefetch_block_bitmaps, Opt_mb_optimize_scan,
 	Opt_errors, Opt_data, Opt_data_err, Opt_jqfmt, Opt_dax_type,
+	Opt_provision, Opt_noprovision,
 #ifdef CONFIG_EXT4_DEBUG
 	Opt_fc_debug_max_replay, Opt_fc_debug_force
 #endif
@@ -1744,6 +1745,8 @@ static const struct fs_parameter_spec ext4_param_specs[] = {
 	fsparam_flag	("reservation",		Opt_removed),	/* mount option from ext2/3 */
 	fsparam_flag	("noreservation",	Opt_removed),	/* mount option from ext2/3 */
 	fsparam_u32	("journal",		Opt_removed),	/* mount option from ext2/3 */
+	fsparam_flag	("discard",		Opt_provision),
+	fsparam_flag	("noprovision",		Opt_noprovision),
 	{}
 };
 
@@ -1840,6 +1843,8 @@ static const struct mount_opts {
 	{Opt_nombcache, EXT4_MOUNT_NO_MBCACHE, MOPT_SET},
 	{Opt_no_prefetch_block_bitmaps, EXT4_MOUNT_NO_PREFETCH_BLOCK_BITMAPS,
 	 MOPT_SET},
+	{Opt_provision, EXT4_MOUNT2_PROVISION, MOPT_SET | MOPT_2},
+	{Opt_noprovision, EXT4_MOUNT2_PROVISION, MOPT_CLEAR | MOPT_2},
 #ifdef CONFIG_EXT4_DEBUG
 	{Opt_fc_debug_force, EXT4_MOUNT2_JOURNAL_FAST_COMMIT,
 	 MOPT_SET | MOPT_2 | MOPT_EXT4_ONLY},
@@ -3010,6 +3015,8 @@ static int _ext4_show_options(struct seq_file *seq, struct super_block *sb,
 		SEQ_OPTS_PUTS("dax=never");
 	} else if (test_opt2(sb, DAX_INODE)) {
 		SEQ_OPTS_PUTS("dax=inode");
+	} else if (test_opt2(sb, PROVISION)) {
+		SEQ_OPTS_PUTS("provision");
 	}
 
 	if (sbi->s_groups_count >= MB_DEFAULT_LINEAR_SCAN_THRESHOLD &&
-- 
2.31.0