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Date: Sat, 24 May 2014 12:02:39 +0400
From: Azat Khuzhin <a3at.mail@...il.com>
To: Miklos Szeredi <miklos@...redi.hu>
Cc: viro@...IV.linux.org.uk, torvalds@...ux-foundation.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
hch@...radead.org, akpm@...ux-foundation.org, apw@...onical.com,
nbd@...nwrt.org, neilb@...e.de, jordipujolp@...il.com,
ezk@....cs.sunysb.edu, dhowells@...hat.com, sedat.dilek@...il.com,
hooanon05@...oo.co.jp, mszeredi@...e.cz
Subject: Re: [PATCH 07/13] vfs: add RENAME_WHITEOUT
On Fri, May 23, 2014 at 11:43:37AM +0200, Miklos Szeredi wrote:
> From: Miklos Szeredi <mszeredi@...e.cz>
>
> This adds a new RENAME_WHITEOUT flag. This flag makes rename() create a
> whiteout of source. The whiteout creation is atomic relative to the
> rename.
>
> Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
> ---
> fs/ext4/namei.c | 99 ++++++++++++++++++++++++++++++++++++++++---------
> fs/namei.c | 8 +++-
> include/linux/fs.h | 7 ++++
> include/uapi/linux/fs.h | 1 +
> 4 files changed, 95 insertions(+), 20 deletions(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index 1cb84f78909e..f782831b19dc 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -3148,6 +3148,39 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
> }
> }
>
> +static struct inode *ext4_whiteout_for_rename(struct ext4_renament *ent,
> + int credits, handle_t **h)
> +{
> + struct inode *wh;
> + handle_t *handle;
> + int retries = 0;
> +
> + /*
> + * for inode block, sb block, group summaries,
> + * and inode bitmap
> + */
> + credits += (EXT4_MAXQUOTAS_TRANS_BLOCKS(ent->dir->i_sb) +
> + EXT4_XATTR_TRANS_BLOCKS + 4);
> +retry:
> + wh = ext4_new_inode_start_handle(ent->dir, S_IFCHR | WHITEOUT_MODE,
> + &ent->dentry->d_name, 0, NULL,
> + EXT4_HT_DIR, credits);
> +
> + handle = ext4_journal_current_handle();
> + if (IS_ERR(wh)) {
> + if (handle)
> + ext4_journal_stop(handle);
> + if (PTR_ERR(wh) == -ENOSPC &&
> + ext4_should_retry_alloc(ent->dir->i_sb, &retries))
> + goto retry;
> + } else {
> + *h = handle;
> + init_special_inode(wh, wh->i_mode, WHITEOUT_DEV);
> + wh->i_op = &ext4_special_inode_operations;
> + }
> + return wh;
> +}
> +
> /*
> * Anybody can rename anything with this: the permission checks are left to the
> * higher-level routines.
> @@ -3156,8 +3189,9 @@ static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
> * while new_{dentry,inode) refers to the destination dentry/inode
> * This comes from rename(const char *oldpath, const char *newpath)
> */
> -static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> - struct inode *new_dir, struct dentry *new_dentry)
> +static int ext4_simple_rename(struct inode *old_dir, struct dentry *old_dentry,
> + struct inode *new_dir, struct dentry *new_dentry,
> + unsigned int flags)
> {
> handle_t *handle = NULL;
> struct ext4_renament old = {
> @@ -3171,6 +3205,9 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> .inode = new_dentry->d_inode,
> };
> int retval;
> + struct inode *whiteout = NULL;
> + int credits;
> + u8 old_file_type;
>
> dquot_initialize(old.dir);
> dquot_initialize(new.dir);
> @@ -3202,11 +3239,17 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> if (new.inode && !test_opt(new.dir->i_sb, NO_AUTO_DA_ALLOC))
> ext4_alloc_da_blocks(old.inode);
>
> - handle = ext4_journal_start(old.dir, EXT4_HT_DIR,
> - (2 * EXT4_DATA_TRANS_BLOCKS(old.dir->i_sb) +
> - EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2));
> - if (IS_ERR(handle))
> - return PTR_ERR(handle);
> + credits = (2 * EXT4_DATA_TRANS_BLOCKS(old.dir->i_sb) +
> + EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2);
> + if (!(flags & RENAME_WHITEOUT)) {
> + handle = ext4_journal_start(old.dir, EXT4_HT_DIR, credits);
> + if (IS_ERR(handle))
> + return PTR_ERR(handle);
> + } else {
> + whiteout = ext4_whiteout_for_rename(&old, credits, &handle);
> + if (IS_ERR(whiteout))
> + return PTR_ERR(whiteout);
> + }
>
> if (IS_DIRSYNC(old.dir) || IS_DIRSYNC(new.dir))
> ext4_handle_sync(handle);
> @@ -3225,13 +3268,21 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> if (retval)
> goto end_rename;
> }
> + old_file_type = old.de->file_type;
> + if (whiteout) {
> + retval = ext4_setent(handle, &old, whiteout->i_ino,
> + EXT4_FT_CHRDEV);
> + if (retval)
> + goto end_rename;
> + ext4_mark_inode_dirty(handle, whiteout);
> + }
> if (!new.bh) {
> retval = ext4_add_entry(handle, new.dentry, old.inode);
> if (retval)
> goto end_rename;
> } else {
> retval = ext4_setent(handle, &new,
> - old.inode->i_ino, old.de->file_type);
> + old.inode->i_ino, old_file_type);
> if (retval)
> goto end_rename;
> }
> @@ -3243,10 +3294,12 @@ static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> old.inode->i_ctime = ext4_current_time(old.inode);
> ext4_mark_inode_dirty(handle, old.inode);
>
> - /*
> - * ok, that's it
> - */
> - ext4_rename_delete(handle, &old);
> + if (!whiteout) {
> + /*
> + * ok, that's it
> + */
> + ext4_rename_delete(handle, &old);
> + }
>
> if (new.inode) {
> ext4_dec_count(handle, new.inode);
> @@ -3282,6 +3335,12 @@ end_rename:
> brelse(old.dir_bh);
> brelse(old.bh);
> brelse(new.bh);
> + if (whiteout) {
> + if (retval)
> + drop_nlink(whiteout);
> + unlock_new_inode(whiteout);
> + iput(whiteout);
> + }
> if (handle)
> ext4_journal_stop(handle);
> return retval;
> @@ -3403,22 +3462,26 @@ end_rename:
> return retval;
> }
>
> +static int ext4_rename(struct inode *old_dir, struct dentry *old_dentry,
> + struct inode *new_dir, struct dentry *new_dentry)
> +{
> + return ext4_simple_rename(old_dir, old_dentry, new_dir, new_dentry, 0);
> +}
> +
> static int ext4_rename2(struct inode *old_dir, struct dentry *old_dentry,
> struct inode *new_dir, struct dentry *new_dentry,
> unsigned int flags)
> {
> - if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
> + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
> return -EINVAL;
>
> if (flags & RENAME_EXCHANGE) {
> return ext4_cross_rename(old_dir, old_dentry,
> new_dir, new_dentry);
> }
> - /*
> - * Existence checking was done by the VFS, otherwise "RENAME_NOREPLACE"
> - * is equivalent to regular rename.
> - */
> - return ext4_rename(old_dir, old_dentry, new_dir, new_dentry);
> +
> + return ext4_simple_rename(old_dir, old_dentry,
> + new_dir, new_dentry, flags);
> }
>
> /*
> diff --git a/fs/namei.c b/fs/namei.c
> index 413d7c138e95..adaa73d91173 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -4186,12 +4186,16 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
> bool should_retry = false;
> int error;
>
> - if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
> + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE | RENAME_WHITEOUT))
> return -EINVAL;
>
> - if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
> + if ((flags & (RENAME_NOREPLACE | RENAME_WHITEOUT)) &&
> + (flags & RENAME_EXCHANGE))
> return -EINVAL;
>
> + if ((flags & RENAME_WHITEOUT) && !capable(CAP_MKNOD))
> + return -EPERM;
> +
> retry:
> from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
> if (IS_ERR(from)) {
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 88ec7a2878bc..48d3bd908b5d 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -228,6 +228,13 @@ typedef void (dio_iodone_t)(struct kiocb *iocb, loff_t offset,
> #define WHITEOUT_DEV 0
>
> /*
> + * Whiteout is represented by a char device. The following constants define the
> + * mode and device number to use.
> + */
> +#define WHITEOUT_MODE 0
> +#define WHITEOUT_DEV 0
Quick note:
I suppose that there is no need in duplicating of WHITEOUT_{MODE,DEV}
Thanks.
> +
> +/*
> * This is the Inode Attributes structure, used for notify_change(). It
> * uses the above definitions as flags, to know which values have changed.
> * Also, in this manner, a Filesystem can look at only the values it cares
> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
> index ca1a11bb4443..3735fa0a6784 100644
> --- a/include/uapi/linux/fs.h
> +++ b/include/uapi/linux/fs.h
> @@ -37,6 +37,7 @@
>
> #define RENAME_NOREPLACE (1 << 0) /* Don't overwrite target */
> #define RENAME_EXCHANGE (1 << 1) /* Exchange source and dest */
> +#define RENAME_WHITEOUT (1 << 2) /* Whiteout source */
>
> struct fstrim_range {
> __u64 start;
> --
> 1.8.1.4
>
> --
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--
Respectfully
Azat Khuzhin
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