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Message-Id: <C9F75389-C7EB-4139-988C-A2CD89FF1097@dilger.ca>
Date: Fri, 21 Oct 2016 12:31:58 -0600
From: Andreas Dilger <adilger@...ger.ca>
To: Fabian Frederick <fabf@...net.be>
Cc: tytso@....edu, Andreas Dilger <adilger.kernel@...ger.ca>,
linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org
Subject: Re: [PATCH V2 linux-next] ext4: make online resizing conditional
On Oct 21, 2016, at 12:16 PM, Fabian Frederick <fabf@...net.be> wrote:
>
> This patch tries to address the following comment in ext4/resize.c
> "This could probably be made into a module, because it is not often in use."
>
> Having ext4 resizing in a module would give a lot of depmod
> dependency cycles but we can make it an option.
>
> resize.h has been added for more readability.
>
> Tried the following resizing:
> dd if=/dev/zero of=ddext4 bs=1M count=100
> losetup -f ddext4
> mkfs -t ext4 /dev/loop0
> losetup -D
> dd if=/dev/zero of=ddappend bs=1M count=50
> cat ddappend >> ddext4
> losetup -f ddext4
> mount /dev/loop0 /mnt
> resize2fs /dev/loop0
>
> With option disabled:
> "Operation not supported While checking for on-line resizing support"
>
> Signed-off-by: Fabian Frederick <fabf@...net.be>
Reviewed-by: Andreas Dilger <adilger@...ger.ca>
> ---
>
> V2:
>
> -Fix checkpatch warnings on identifier names like:
> WARNING: function definition argument 'struct super_block *'
> should also have an identifier name
> #130: FILE: fs/ext4/resize.h:8:
> +extern int ext4_resize_fs(struct super_block *, ext4_fsblk_t);
>
> -Reorder extern functions in resize.h to match -EOPNOTSUPP definitions
>
> -Rename EXT4_RESIZING to EXT4_RESIZING_ACTIVE
> (Andreas Dilger suggested EXT4_RESIZE_ACTIVE but we already have
> EXT4_RESIZE_INO in another context)
>
> Other suggestions by Andreas:
>
> -Add comment to s_resize_flags for EXT4_RESIZING_* bits
> -Leave the module comment in resize.h
> -Use ifdef CONFIG instead of IS_ENABLED()
>
> fs/ext4/Kconfig | 7 +++++++
> fs/ext4/Makefile | 3 ++-
> fs/ext4/ext4.h | 16 +++-------------
> fs/ext4/ioctl.c | 1 +
> fs/ext4/resize.c | 6 ++++--
> fs/ext4/resize.h | 42 ++++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 59 insertions(+), 16 deletions(-)
> create mode 100644 fs/ext4/resize.h
>
> diff --git a/fs/ext4/Kconfig b/fs/ext4/Kconfig
> index e38039f..2ec35c3 100644
> --- a/fs/ext4/Kconfig
> +++ b/fs/ext4/Kconfig
> @@ -122,3 +122,10 @@ config EXT4_DEBUG
> If you select Y here, then you will be able to turn on debugging
> with a command such as:
> echo 1 > /sys/module/ext4/parameters/mballoc_debug
> +
> +config EXT4_RESIZE
> + bool "EXT4 resize"
> + depends on EXT4_FS
> + default y
> + help
> + Support online ext4 partition resizing.
> diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
> index 354103f..efe6579 100644
> --- a/fs/ext4/Makefile
> +++ b/fs/ext4/Makefile
> @@ -5,10 +5,11 @@
> obj-$(CONFIG_EXT4_FS) += ext4.o
>
> ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
> - ioctl.o namei.o super.o symlink.o hash.o resize.o extents.o \
> + ioctl.o namei.o super.o symlink.o hash.o extents.o \
> ext4_jbd2.o migrate.o mballoc.o block_validity.o move_extent.o \
> mmp.o indirect.o extents_status.o xattr.o xattr_user.o \
> xattr_trusted.o inline.o readpage.o sysfs.o
>
> ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o
> ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
> +ext4-$(CONFIG_EXT4_RESIZE) += resize.o
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index 282a51b..542ebc2 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1403,7 +1403,9 @@ struct ext4_sb_info {
> struct list_head s_orphan;
> struct mutex s_orphan_lock;
> unsigned long s_resize_flags; /* Flags indicating if there
> - is a resizer */
> + * is a resizer using
> + * EXT4_RESIZING_* bits
> + */
> unsigned long s_commit_interval;
> u32 s_max_batch_time;
> u32 s_min_batch_time;
> @@ -2555,14 +2557,6 @@ extern int ext4_generic_delete_entry(handle_t *handle,
> int csum_size);
> extern bool ext4_empty_dir(struct inode *inode);
>
> -/* resize.c */
> -extern int ext4_group_add(struct super_block *sb,
> - struct ext4_new_group_data *input);
> -extern int ext4_group_extend(struct super_block *sb,
> - struct ext4_super_block *es,
> - ext4_fsblk_t n_blocks_count);
> -extern int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count);
> -
> /* super.c */
> extern int ext4_seq_options_show(struct seq_file *seq, void *offset);
> extern int ext4_calculate_overhead(struct super_block *sb);
> @@ -3239,10 +3233,6 @@ static inline void ext4_inode_resume_unlocked_dio(struct inode *inode)
> EXT4_WQ_HASH_SZ])
> extern wait_queue_head_t ext4__ioend_wq[EXT4_WQ_HASH_SZ];
>
> -#define EXT4_RESIZING 0
> -extern int ext4_resize_begin(struct super_block *sb);
> -extern void ext4_resize_end(struct super_block *sb);
> -
> static inline void ext4_set_io_unwritten_flag(struct inode *inode,
> struct ext4_io_end *io_end)
> {
> diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
> index bf5ae8e..81d28d2 100644
> --- a/fs/ext4/ioctl.c
> +++ b/fs/ext4/ioctl.c
> @@ -18,6 +18,7 @@
> #include <asm/uaccess.h>
> #include "ext4_jbd2.h"
> #include "ext4.h"
> +#include "resize.h"
>
> /**
> * Swap memory between @a and @b for @len bytes.
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index cf68100..4c7cd75 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -15,6 +15,7 @@
> #include <linux/slab.h>
>
> #include "ext4_jbd2.h"
> +#include "resize.h"
>
> int ext4_resize_begin(struct super_block *sb)
> {
> @@ -45,7 +46,8 @@ int ext4_resize_begin(struct super_block *sb)
> return -EPERM;
> }
>
> - if (test_and_set_bit_lock(EXT4_RESIZING, &EXT4_SB(sb)->s_resize_flags))
> + if (test_and_set_bit_lock(EXT4_RESIZING_ACTIVE,
> + &EXT4_SB(sb)->s_resize_flags))
> ret = -EBUSY;
>
> return ret;
> @@ -53,7 +55,7 @@ int ext4_resize_begin(struct super_block *sb)
>
> void ext4_resize_end(struct super_block *sb)
> {
> - clear_bit_unlock(EXT4_RESIZING, &EXT4_SB(sb)->s_resize_flags);
> + clear_bit_unlock(EXT4_RESIZING_ACTIVE, &EXT4_SB(sb)->s_resize_flags);
> smp_mb__after_atomic();
> }
>
> diff --git a/fs/ext4/resize.h b/fs/ext4/resize.h
> new file mode 100644
> index 0000000..df15285
> --- /dev/null
> +++ b/fs/ext4/resize.h
> @@ -0,0 +1,42 @@
> +/*
> + * linux/fs/ext4/resize.h
> + *
> + */
> +
> +#ifdef CONFIG_EXT4_RESIZE
> +#define EXT4_RESIZING_ACTIVE 0
> +extern int ext4_resize_begin(struct super_block *sb);
> +extern void ext4_resize_end(struct super_block *sb);
> +extern int ext4_group_add(struct super_block *sb,
> + struct ext4_new_group_data *input);
> +extern int ext4_group_extend(struct super_block *sb,
> + struct ext4_super_block *es, ext4_fsblk_t n_blocks_count);
> +extern int ext4_resize_fs(struct super_block *sb, ext4_fsblk_t n_blocks_count);
> +#else
> +static int ext4_resize_begin(struct super_block *sb)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static void ext4_resize_end(struct super_block *sb)
> +{
> +}
> +
> +static inline int ext4_group_add(struct super_block *sb,
> + struct ext4_new_group_data *input)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline int ext4_group_extend(struct super_block *sb,
> + struct ext4_super_block *es, ext4_fsblk_t n_blocks_count)
> +{
> + return -EOPNOTSUPP;
> +}
> +
> +static inline int ext4_resize_fs(struct super_block *sb,
> + ext4_fsblk_t n_blocks_count)
> +{
> + return -EOPNOTSUPP;
> +}
> +#endif
> --
> 2.7.4
>
Cheers, Andreas
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