Message-ID: <YboL1hpl4JKCKHfn@suse.de>
Date:   Wed, 15 Dec 2021 15:37:58 +0000
From:   Luís Henriques <lhenriques@...e.de>
To:     Lukas Czerner <lczerner@...hat.com>
Cc:     Jan Kara <jack@...e.cz>, "Darrick J. Wong" <djwong@...nel.org>,
        Theodore Ts'o <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jonathan Corbet <corbet@....net>, linux-ext4@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Jeroen van Wolffelaar <jeroen@...ffelaar.nl>
Subject: Re: [PATCH v2] ext4: set csum seed in tmp inode while migrating to
 extents

On Wed, Dec 15, 2021 at 03:12:37PM +0100, Lukas Czerner wrote:
> On Wed, Dec 15, 2021 at 12:28:52PM +0100, Jan Kara wrote:
> > On Tue 14-12-21 16:49:45, Darrick J. Wong wrote:
> > > On Tue, Dec 14, 2021 at 05:50:58PM +0000, Luís Henriques wrote:
> > > > When migrating to extents, the temporary inode will have it's own checksum
> > > > seed.  This means that, when swapping the inodes data, the inode checksums
> > > > will be incorrect.
> > > > 
> > > > This can be fixed by recalculating the extents checksums again.  Or simply
> > > > by copying the seed into the temporary inode.
> > > > 
> > > > Link: https://bugzilla.kernel.org/show_bug.cgi?id=213357
> > > > Reported-by: Jeroen van Wolffelaar <jeroen@...ffelaar.nl>
> > > > Signed-off-by: Luís Henriques <lhenriques@...e.de>
> > > > ---
> > > >  fs/ext4/migrate.c | 12 +++++++++++-
> > > >  1 file changed, 11 insertions(+), 1 deletion(-)
> > > > 
> > > > changes since v1:
> > > > 
> > > > * Dropped tmp_ei variable
> > > > * ->i_csum_seed is now initialised immediately after tmp_inode is created
> > > > * New comment about the seed initialization and stating that recovery
> > > >   needs to be fixed.
> > > > 
> > > > Cheers,
> > > > --
> > > > Luís
> > > > 
> > > > diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> > > > index 7e0b4f81c6c0..36dfc88ce05b 100644
> > > > --- a/fs/ext4/migrate.c
> > > > +++ b/fs/ext4/migrate.c
> > > > @@ -459,6 +459,17 @@ int ext4_ext_migrate(struct inode *inode)
> > > >  		ext4_journal_stop(handle);
> > > >  		goto out_unlock;
> > > >  	}
> > > > +	/*
> > > > +	 * Use the correct seed for checksum (i.e. the seed from 'inode').  This
> > > > +	 * is so that the metadata blocks will have the correct checksum after
> > > > +	 * the migration.
> > > > +	 *
> > > > +	 * Note however that, if a crash occurs during the migration process,
> > > > +	 * the recovery process is broken because the tmp_inode checksums will
> > > > +	 * be wrong and the orphans cleanup will fail.
> > > 
> > > ...and then what does the user do?
> > 
> > Run fsck of course! And then recover from backups :) I know this is sad but
> > the situation is that our migration code just is not crash-safe (if we
> > crash we are going to free blocks that are still used by the migrated
> > inode) and Luis makes it work in case we do not crash (which should be
> > hopefully more common) and documents it does not work in case we crash.
> > So overall I'd call it a win.
> > 
> > But maybe we should just remove this online-migration functionality
> > completely from the kernel? That would be also a fine solution for me. I
> > was thinking whether we could somehow make the inode migration crash-safe
> > but I didn't think of anything which would not require on-disk format
> > change...
> 
> Since this is not something that anyone can honestly recommend doing
> without a prior backup and a word of warning I personaly would be in favor
> of removing it.

It's odd that my first fix to ext4 ends up wiping out a whole feature :-)

Anyway, in case the decision is to go ahead with the feature removal, I'm
inlining bellow an RFC that simply removes the whole file (and returns
-EOPNOTSUPP in the appropriate places).  This was only compile-tested, so
I may have missed something.

(Oh, I almost forgot: I also wanted to mention the word dromedary just to
mess a little bit with Jon's article in tomorrow's LWN :-) )

Cheers,
--
Luís

>From 19810c891ca612fafbfdeeea6651ba5484d5039f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lu=C3=ADs=20Henriques?= <lhenriques@...e.de>
Date: Wed, 15 Dec 2021 15:10:26 +0000
Subject: [RFC PATCH] ext4: remove online-migration feature from the kernel
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Online migration is currently broken (see link bellow).  Although this
specific issue could be easily fixed, it seems to be very difficult to
implement it in a safe manner so that recovery can be done without risking
loosing data.  Instead of changing on-disk format, simply wipe the whole
feature.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=213357
Reported-by: Jeroen van Wolffelaar <jeroen@...ffelaar.nl>
Signed-off-by: Luís Henriques <lhenriques@...e.de>
---
 fs/ext4/Makefile  |   2 +-
 fs/ext4/ext4.h    |   4 -
 fs/ext4/ioctl.c   |  33 +--
 fs/ext4/migrate.c | 669 ----------------------------------------------
 4 files changed, 7 insertions(+), 701 deletions(-)
 delete mode 100644 fs/ext4/migrate.c

diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
index 7d89142e1421..d904a1cbc3d8 100644
--- a/fs/ext4/Makefile
+++ b/fs/ext4/Makefile
@@ -7,7 +7,7 @@ obj-$(CONFIG_EXT4_FS) += ext4.o
 
 ext4-y	:= balloc.o bitmap.o block_validity.o dir.o ext4_jbd2.o extents.o \
 		extents_status.o file.o fsmap.o fsync.o hash.o ialloc.o \
-		indirect.o inline.o inode.o ioctl.o mballoc.o migrate.o \
+		indirect.o inline.o inode.o ioctl.o mballoc.o \
 		mmp.o move_extent.o namei.o page-io.o readpage.o resize.o \
 		super.o symlink.o sysfs.o xattr.o xattr_hurd.o xattr_trusted.o \
 		xattr_user.o fast_commit.o orphan.o
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 404dd50856e5..7b92120cb560 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -3062,10 +3062,6 @@ int ext4_fileattr_set(struct user_namespace *mnt_userns,
 int ext4_fileattr_get(struct dentry *dentry, struct fileattr *fa);
 extern void ext4_reset_inode_seed(struct inode *inode);
 
-/* migrate.c */
-extern int ext4_ext_migrate(struct inode *);
-extern int ext4_ind_migrate(struct inode *inode);
-
 /* namei.c */
 extern int ext4_init_new_dir(handle_t *handle, struct inode *dir,
 			     struct inode *inode);
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index 606dee9e08a3..07f8461f69da 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -341,7 +341,7 @@ static int ext4_ioctl_setflags(struct inode *inode,
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);
 	handle_t *handle = NULL;
-	int err = -EPERM, migrate = 0;
+	int err = -EPERM;
 	struct ext4_iloc iloc;
 	unsigned int oldflags, mask, i;
 	struct super_block *sb = inode->i_sb;
@@ -365,8 +365,10 @@ static int ext4_ioctl_setflags(struct inode *inode,
 		goto flags_out;
 	}
 
-	if ((flags ^ oldflags) & EXT4_EXTENTS_FL)
-		migrate = 1;
+	if ((flags ^ oldflags) & EXT4_EXTENTS_FL) {
+		err = -EOPNOTSUPP;
+		goto flags_out;
+	}
 
 	if ((flags ^ oldflags) & EXT4_CASEFOLD_FL) {
 		if (!ext4_has_feature_casefold(sb)) {
@@ -449,12 +451,6 @@ static int ext4_ioctl_setflags(struct inode *inode,
 		if (err)
 			goto flags_out;
 	}
-	if (migrate) {
-		if (flags & EXT4_EXTENTS_FL)
-			err = ext4_ext_migrate(inode);
-		else
-			err = ext4_ind_migrate(inode);
-	}
 
 flags_out:
 	return err;
@@ -1009,24 +1005,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 
 	case EXT4_IOC_MIGRATE:
 	{
-		int err;
-		if (!inode_owner_or_capable(mnt_userns, inode))
-			return -EACCES;
-
-		err = mnt_want_write_file(filp);
-		if (err)
-			return err;
-		/*
-		 * inode_mutex prevent write and truncate on the file.
-		 * Read still goes through. We take i_data_sem in
-		 * ext4_ext_swap_inode_data before we switch the
-		 * inode format to prevent read.
-		 */
-		inode_lock((inode));
-		err = ext4_ext_migrate(inode);
-		inode_unlock((inode));
-		mnt_drop_write_file(filp);
-		return err;
+		return -EOPNOTSUPP;
 	}
 
 	case EXT4_IOC_ALLOC_DA_BLKS:
diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
deleted file mode 100644
index 7e0b4f81c6c0..000000000000
--- a/fs/ext4/migrate.c
+++ /dev/null
@@ -1,669 +0,0 @@
-// SPDX-License-Identifier: LGPL-2.1
-/*
- * Copyright IBM Corporation, 2007
- * Author Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
- *
- */
-
-#include <linux/slab.h>
-#include "ext4_jbd2.h"
-#include "ext4_extents.h"
-
-/*
- * The contiguous blocks details which can be
- * represented by a single extent
- */
-struct migrate_struct {
-	ext4_lblk_t first_block, last_block, curr_block;
-	ext4_fsblk_t first_pblock, last_pblock;
-};
-
-static int finish_range(handle_t *handle, struct inode *inode,
-				struct migrate_struct *lb)
-
-{
-	int retval = 0, needed;
-	struct ext4_extent newext;
-	struct ext4_ext_path *path;
-	if (lb->first_pblock == 0)
-		return 0;
-
-	/* Add the extent to temp inode*/
-	newext.ee_block = cpu_to_le32(lb->first_block);
-	newext.ee_len   = cpu_to_le16(lb->last_block - lb->first_block + 1);
-	ext4_ext_store_pblock(&newext, lb->first_pblock);
-	/* Locking only for convenience since we are operating on temp inode */
-	down_write(&EXT4_I(inode)->i_data_sem);
-	path = ext4_find_extent(inode, lb->first_block, NULL, 0);
-	if (IS_ERR(path)) {
-		retval = PTR_ERR(path);
-		path = NULL;
-		goto err_out;
-	}
-
-	/*
-	 * Calculate the credit needed to inserting this extent
-	 * Since we are doing this in loop we may accumulate extra
-	 * credit. But below we try to not accumulate too much
-	 * of them by restarting the journal.
-	 */
-	needed = ext4_ext_calc_credits_for_single_extent(inode,
-		    lb->last_block - lb->first_block + 1, path);
-
-	retval = ext4_datasem_ensure_credits(handle, inode, needed, needed, 0);
-	if (retval < 0)
-		goto err_out;
-	retval = ext4_ext_insert_extent(handle, inode, &path, &newext, 0);
-err_out:
-	up_write((&EXT4_I(inode)->i_data_sem));
-	ext4_ext_drop_refs(path);
-	kfree(path);
-	lb->first_pblock = 0;
-	return retval;
-}
-
-static int update_extent_range(handle_t *handle, struct inode *inode,
-			       ext4_fsblk_t pblock, struct migrate_struct *lb)
-{
-	int retval;
-	/*
-	 * See if we can add on to the existing range (if it exists)
-	 */
-	if (lb->first_pblock &&
-		(lb->last_pblock+1 == pblock) &&
-		(lb->last_block+1 == lb->curr_block)) {
-		lb->last_pblock = pblock;
-		lb->last_block = lb->curr_block;
-		lb->curr_block++;
-		return 0;
-	}
-	/*
-	 * Start a new range.
-	 */
-	retval = finish_range(handle, inode, lb);
-	lb->first_pblock = lb->last_pblock = pblock;
-	lb->first_block = lb->last_block = lb->curr_block;
-	lb->curr_block++;
-	return retval;
-}
-
-static int update_ind_extent_range(handle_t *handle, struct inode *inode,
-				   ext4_fsblk_t pblock,
-				   struct migrate_struct *lb)
-{
-	struct buffer_head *bh;
-	__le32 *i_data;
-	int i, retval = 0;
-	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;
-
-	bh = ext4_sb_bread(inode->i_sb, pblock, 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	i_data = (__le32 *)bh->b_data;
-	for (i = 0; i < max_entries; i++) {
-		if (i_data[i]) {
-			retval = update_extent_range(handle, inode,
-						le32_to_cpu(i_data[i]), lb);
-			if (retval)
-				break;
-		} else {
-			lb->curr_block++;
-		}
-	}
-	put_bh(bh);
-	return retval;
-
-}
-
-static int update_dind_extent_range(handle_t *handle, struct inode *inode,
-				    ext4_fsblk_t pblock,
-				    struct migrate_struct *lb)
-{
-	struct buffer_head *bh;
-	__le32 *i_data;
-	int i, retval = 0;
-	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;
-
-	bh = ext4_sb_bread(inode->i_sb, pblock, 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	i_data = (__le32 *)bh->b_data;
-	for (i = 0; i < max_entries; i++) {
-		if (i_data[i]) {
-			retval = update_ind_extent_range(handle, inode,
-						le32_to_cpu(i_data[i]), lb);
-			if (retval)
-				break;
-		} else {
-			/* Only update the file block number */
-			lb->curr_block += max_entries;
-		}
-	}
-	put_bh(bh);
-	return retval;
-
-}
-
-static int update_tind_extent_range(handle_t *handle, struct inode *inode,
-				    ext4_fsblk_t pblock,
-				    struct migrate_struct *lb)
-{
-	struct buffer_head *bh;
-	__le32 *i_data;
-	int i, retval = 0;
-	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;
-
-	bh = ext4_sb_bread(inode->i_sb, pblock, 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	i_data = (__le32 *)bh->b_data;
-	for (i = 0; i < max_entries; i++) {
-		if (i_data[i]) {
-			retval = update_dind_extent_range(handle, inode,
-						le32_to_cpu(i_data[i]), lb);
-			if (retval)
-				break;
-		} else {
-			/* Only update the file block number */
-			lb->curr_block += max_entries * max_entries;
-		}
-	}
-	put_bh(bh);
-	return retval;
-
-}
-
-static int free_dind_blocks(handle_t *handle,
-				struct inode *inode, __le32 i_data)
-{
-	int i;
-	__le32 *tmp_idata;
-	struct buffer_head *bh;
-	struct super_block *sb = inode->i_sb;
-	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;
-	int err;
-
-	bh = ext4_sb_bread(sb, le32_to_cpu(i_data), 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	tmp_idata = (__le32 *)bh->b_data;
-	for (i = 0; i < max_entries; i++) {
-		if (tmp_idata[i]) {
-			err = ext4_journal_ensure_credits(handle,
-				EXT4_RESERVE_TRANS_BLOCKS,
-				ext4_free_metadata_revoke_credits(sb, 1));
-			if (err < 0) {
-				put_bh(bh);
-				return err;
-			}
-			ext4_free_blocks(handle, inode, NULL,
-					 le32_to_cpu(tmp_idata[i]), 1,
-					 EXT4_FREE_BLOCKS_METADATA |
-					 EXT4_FREE_BLOCKS_FORGET);
-		}
-	}
-	put_bh(bh);
-	err = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
-				ext4_free_metadata_revoke_credits(sb, 1));
-	if (err < 0)
-		return err;
-	ext4_free_blocks(handle, inode, NULL, le32_to_cpu(i_data), 1,
-			 EXT4_FREE_BLOCKS_METADATA |
-			 EXT4_FREE_BLOCKS_FORGET);
-	return 0;
-}
-
-static int free_tind_blocks(handle_t *handle,
-				struct inode *inode, __le32 i_data)
-{
-	int i, retval = 0;
-	__le32 *tmp_idata;
-	struct buffer_head *bh;
-	unsigned long max_entries = inode->i_sb->s_blocksize >> 2;
-
-	bh = ext4_sb_bread(inode->i_sb, le32_to_cpu(i_data), 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	tmp_idata = (__le32 *)bh->b_data;
-	for (i = 0; i < max_entries; i++) {
-		if (tmp_idata[i]) {
-			retval = free_dind_blocks(handle,
-					inode, tmp_idata[i]);
-			if (retval) {
-				put_bh(bh);
-				return retval;
-			}
-		}
-	}
-	put_bh(bh);
-	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
-			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
-	if (retval < 0)
-		return retval;
-	ext4_free_blocks(handle, inode, NULL, le32_to_cpu(i_data), 1,
-			 EXT4_FREE_BLOCKS_METADATA |
-			 EXT4_FREE_BLOCKS_FORGET);
-	return 0;
-}
-
-static int free_ind_block(handle_t *handle, struct inode *inode, __le32 *i_data)
-{
-	int retval;
-
-	/* ei->i_data[EXT4_IND_BLOCK] */
-	if (i_data[0]) {
-		retval = ext4_journal_ensure_credits(handle,
-			EXT4_RESERVE_TRANS_BLOCKS,
-			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
-		if (retval < 0)
-			return retval;
-		ext4_free_blocks(handle, inode, NULL,
-				le32_to_cpu(i_data[0]), 1,
-				 EXT4_FREE_BLOCKS_METADATA |
-				 EXT4_FREE_BLOCKS_FORGET);
-	}
-
-	/* ei->i_data[EXT4_DIND_BLOCK] */
-	if (i_data[1]) {
-		retval = free_dind_blocks(handle, inode, i_data[1]);
-		if (retval)
-			return retval;
-	}
-
-	/* ei->i_data[EXT4_TIND_BLOCK] */
-	if (i_data[2]) {
-		retval = free_tind_blocks(handle, inode, i_data[2]);
-		if (retval)
-			return retval;
-	}
-	return 0;
-}
-
-static int ext4_ext_swap_inode_data(handle_t *handle, struct inode *inode,
-						struct inode *tmp_inode)
-{
-	int retval, retval2 = 0;
-	__le32	i_data[3];
-	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_inode_info *tmp_ei = EXT4_I(tmp_inode);
-
-	/*
-	 * One credit accounted for writing the
-	 * i_data field of the original inode
-	 */
-	retval = ext4_journal_ensure_credits(handle, 1, 0);
-	if (retval < 0)
-		goto err_out;
-
-	i_data[0] = ei->i_data[EXT4_IND_BLOCK];
-	i_data[1] = ei->i_data[EXT4_DIND_BLOCK];
-	i_data[2] = ei->i_data[EXT4_TIND_BLOCK];
-
-	down_write(&EXT4_I(inode)->i_data_sem);
-	/*
-	 * if EXT4_STATE_EXT_MIGRATE is cleared a block allocation
-	 * happened after we started the migrate. We need to
-	 * fail the migrate
-	 */
-	if (!ext4_test_inode_state(inode, EXT4_STATE_EXT_MIGRATE)) {
-		retval = -EAGAIN;
-		up_write(&EXT4_I(inode)->i_data_sem);
-		goto err_out;
-	} else
-		ext4_clear_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
-	/*
-	 * We have the extent map build with the tmp inode.
-	 * Now copy the i_data across
-	 */
-	ext4_set_inode_flag(inode, EXT4_INODE_EXTENTS);
-	memcpy(ei->i_data, tmp_ei->i_data, sizeof(ei->i_data));
-
-	/*
-	 * Update i_blocks with the new blocks that got
-	 * allocated while adding extents for extent index
-	 * blocks.
-	 *
-	 * While converting to extents we need not
-	 * update the original inode i_blocks for extent blocks
-	 * via quota APIs. The quota update happened via tmp_inode already.
-	 */
-	spin_lock(&inode->i_lock);
-	inode->i_blocks += tmp_inode->i_blocks;
-	spin_unlock(&inode->i_lock);
-	up_write(&EXT4_I(inode)->i_data_sem);
-
-	/*
-	 * We mark the inode dirty after, because we decrement the
-	 * i_blocks when freeing the indirect meta-data blocks
-	 */
-	retval = free_ind_block(handle, inode, i_data);
-	retval2 = ext4_mark_inode_dirty(handle, inode);
-	if (unlikely(retval2 && !retval))
-		retval = retval2;
-
-err_out:
-	return retval;
-}
-
-static int free_ext_idx(handle_t *handle, struct inode *inode,
-					struct ext4_extent_idx *ix)
-{
-	int i, retval = 0;
-	ext4_fsblk_t block;
-	struct buffer_head *bh;
-	struct ext4_extent_header *eh;
-
-	block = ext4_idx_pblock(ix);
-	bh = ext4_sb_bread(inode->i_sb, block, 0);
-	if (IS_ERR(bh))
-		return PTR_ERR(bh);
-
-	eh = (struct ext4_extent_header *)bh->b_data;
-	if (eh->eh_depth != 0) {
-		ix = EXT_FIRST_INDEX(eh);
-		for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ix++) {
-			retval = free_ext_idx(handle, inode, ix);
-			if (retval) {
-				put_bh(bh);
-				return retval;
-			}
-		}
-	}
-	put_bh(bh);
-	retval = ext4_journal_ensure_credits(handle, EXT4_RESERVE_TRANS_BLOCKS,
-			ext4_free_metadata_revoke_credits(inode->i_sb, 1));
-	if (retval < 0)
-		return retval;
-	ext4_free_blocks(handle, inode, NULL, block, 1,
-			 EXT4_FREE_BLOCKS_METADATA | EXT4_FREE_BLOCKS_FORGET);
-	return 0;
-}
-
-/*
- * Free the extent meta data blocks only
- */
-static int free_ext_block(handle_t *handle, struct inode *inode)
-{
-	int i, retval = 0;
-	struct ext4_inode_info *ei = EXT4_I(inode);
-	struct ext4_extent_header *eh = (struct ext4_extent_header *)ei->i_data;
-	struct ext4_extent_idx *ix;
-	if (eh->eh_depth == 0)
-		/*
-		 * No extra blocks allocated for extent meta data
-		 */
-		return 0;
-	ix = EXT_FIRST_INDEX(eh);
-	for (i = 0; i < le16_to_cpu(eh->eh_entries); i++, ix++) {
-		retval = free_ext_idx(handle, inode, ix);
-		if (retval)
-			return retval;
-	}
-	return retval;
-}
-
-int ext4_ext_migrate(struct inode *inode)
-{
-	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
-	handle_t *handle;
-	int retval = 0, i;
-	__le32 *i_data;
-	struct ext4_inode_info *ei;
-	struct inode *tmp_inode = NULL;
-	struct migrate_struct lb;
-	unsigned long max_entries;
-	__u32 goal;
-	uid_t owner[2];
-
-	/*
-	 * If the filesystem does not support extents, or the inode
-	 * already is extent-based, error out.
-	 */
-	if (!ext4_has_feature_extents(inode->i_sb) ||
-	    (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
-		return -EINVAL;
-
-	if (S_ISLNK(inode->i_mode) && inode->i_blocks == 0)
-		/*
-		 * don't migrate fast symlink
-		 */
-		return retval;
-
-	percpu_down_write(&sbi->s_writepages_rwsem);
-
-	/*
-	 * Worst case we can touch the allocation bitmaps, a bgd
-	 * block, and a block to link in the orphan list.  We do need
-	 * need to worry about credits for modifying the quota inode.
-	 */
-	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE,
-		4 + EXT4_MAXQUOTAS_TRANS_BLOCKS(inode->i_sb));
-
-	if (IS_ERR(handle)) {
-		retval = PTR_ERR(handle);
-		goto out_unlock;
-	}
-	goal = (((inode->i_ino - 1) / EXT4_INODES_PER_GROUP(inode->i_sb)) *
-		EXT4_INODES_PER_GROUP(inode->i_sb)) + 1;
-	owner[0] = i_uid_read(inode);
-	owner[1] = i_gid_read(inode);
-	tmp_inode = ext4_new_inode(handle, d_inode(inode->i_sb->s_root),
-				   S_IFREG, NULL, goal, owner, 0);
-	if (IS_ERR(tmp_inode)) {
-		retval = PTR_ERR(tmp_inode);
-		ext4_journal_stop(handle);
-		goto out_unlock;
-	}
-	i_size_write(tmp_inode, i_size_read(inode));
-	/*
-	 * Set the i_nlink to zero so it will be deleted later
-	 * when we drop inode reference.
-	 */
-	clear_nlink(tmp_inode);
-
-	ext4_ext_tree_init(handle, tmp_inode);
-	ext4_orphan_add(handle, tmp_inode);
-	ext4_journal_stop(handle);
-
-	/*
-	 * start with one credit accounted for
-	 * superblock modification.
-	 *
-	 * For the tmp_inode we already have committed the
-	 * transaction that created the inode. Later as and
-	 * when we add extents we extent the journal
-	 */
-	/*
-	 * Even though we take i_mutex we can still cause block
-	 * allocation via mmap write to holes. If we have allocated
-	 * new blocks we fail migrate.  New block allocation will
-	 * clear EXT4_STATE_EXT_MIGRATE flag.  The flag is updated
-	 * with i_data_sem held to prevent racing with block
-	 * allocation.
-	 */
-	down_read(&EXT4_I(inode)->i_data_sem);
-	ext4_set_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
-	up_read((&EXT4_I(inode)->i_data_sem));
-
-	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
-	if (IS_ERR(handle)) {
-		/*
-		 * It is impossible to update on-disk structures without
-		 * a handle, so just rollback in-core changes and live other
-		 * work to orphan_list_cleanup()
-		 */
-		ext4_orphan_del(NULL, tmp_inode);
-		retval = PTR_ERR(handle);
-		goto out_tmp_inode;
-	}
-
-	ei = EXT4_I(inode);
-	i_data = ei->i_data;
-	memset(&lb, 0, sizeof(lb));
-
-	/* 32 bit block address 4 bytes */
-	max_entries = inode->i_sb->s_blocksize >> 2;
-	for (i = 0; i < EXT4_NDIR_BLOCKS; i++) {
-		if (i_data[i]) {
-			retval = update_extent_range(handle, tmp_inode,
-						le32_to_cpu(i_data[i]), &lb);
-			if (retval)
-				goto err_out;
-		} else
-			lb.curr_block++;
-	}
-	if (i_data[EXT4_IND_BLOCK]) {
-		retval = update_ind_extent_range(handle, tmp_inode,
-				le32_to_cpu(i_data[EXT4_IND_BLOCK]), &lb);
-		if (retval)
-			goto err_out;
-	} else
-		lb.curr_block += max_entries;
-	if (i_data[EXT4_DIND_BLOCK]) {
-		retval = update_dind_extent_range(handle, tmp_inode,
-				le32_to_cpu(i_data[EXT4_DIND_BLOCK]), &lb);
-		if (retval)
-			goto err_out;
-	} else
-		lb.curr_block += max_entries * max_entries;
-	if (i_data[EXT4_TIND_BLOCK]) {
-		retval = update_tind_extent_range(handle, tmp_inode,
-				le32_to_cpu(i_data[EXT4_TIND_BLOCK]), &lb);
-		if (retval)
-			goto err_out;
-	}
-	/*
-	 * Build the last extent
-	 */
-	retval = finish_range(handle, tmp_inode, &lb);
-err_out:
-	if (retval)
-		/*
-		 * Failure case delete the extent information with the
-		 * tmp_inode
-		 */
-		free_ext_block(handle, tmp_inode);
-	else {
-		retval = ext4_ext_swap_inode_data(handle, inode, tmp_inode);
-		if (retval)
-			/*
-			 * if we fail to swap inode data free the extent
-			 * details of the tmp inode
-			 */
-			free_ext_block(handle, tmp_inode);
-	}
-
-	/* We mark the tmp_inode dirty via ext4_ext_tree_init. */
-	retval = ext4_journal_ensure_credits(handle, 1, 0);
-	if (retval < 0)
-		goto out_stop;
-	/*
-	 * Mark the tmp_inode as of size zero
-	 */
-	i_size_write(tmp_inode, 0);
-
-	/*
-	 * set the  i_blocks count to zero
-	 * so that the ext4_evict_inode() does the
-	 * right job
-	 *
-	 * We don't need to take the i_lock because
-	 * the inode is not visible to user space.
-	 */
-	tmp_inode->i_blocks = 0;
-
-	/* Reset the extent details */
-	ext4_ext_tree_init(handle, tmp_inode);
-out_stop:
-	ext4_journal_stop(handle);
-out_tmp_inode:
-	unlock_new_inode(tmp_inode);
-	iput(tmp_inode);
-out_unlock:
-	percpu_up_write(&sbi->s_writepages_rwsem);
-	return retval;
-}
-
-/*
- * Migrate a simple extent-based inode to use the i_blocks[] array
- */
-int ext4_ind_migrate(struct inode *inode)
-{
-	struct ext4_extent_header	*eh;
-	struct ext4_sb_info		*sbi = EXT4_SB(inode->i_sb);
-	struct ext4_super_block		*es = sbi->s_es;
-	struct ext4_inode_info		*ei = EXT4_I(inode);
-	struct ext4_extent		*ex;
-	unsigned int			i, len;
-	ext4_lblk_t			start, end;
-	ext4_fsblk_t			blk;
-	handle_t			*handle;
-	int				ret, ret2 = 0;
-
-	if (!ext4_has_feature_extents(inode->i_sb) ||
-	    (!ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
-		return -EINVAL;
-
-	if (ext4_has_feature_bigalloc(inode->i_sb))
-		return -EOPNOTSUPP;
-
-	/*
-	 * In order to get correct extent info, force all delayed allocation
-	 * blocks to be allocated, otherwise delayed allocation blocks may not
-	 * be reflected and bypass the checks on extent header.
-	 */
-	if (test_opt(inode->i_sb, DELALLOC))
-		ext4_alloc_da_blocks(inode);
-
-	percpu_down_write(&sbi->s_writepages_rwsem);
-
-	handle = ext4_journal_start(inode, EXT4_HT_MIGRATE, 1);
-	if (IS_ERR(handle)) {
-		ret = PTR_ERR(handle);
-		goto out_unlock;
-	}
-
-	down_write(&EXT4_I(inode)->i_data_sem);
-	ret = ext4_ext_check_inode(inode);
-	if (ret)
-		goto errout;
-
-	eh = ext_inode_hdr(inode);
-	ex  = EXT_FIRST_EXTENT(eh);
-	if (ext4_blocks_count(es) > EXT4_MAX_BLOCK_FILE_PHYS ||
-	    eh->eh_depth != 0 || le16_to_cpu(eh->eh_entries) > 1) {
-		ret = -EOPNOTSUPP;
-		goto errout;
-	}
-	if (eh->eh_entries == 0)
-		blk = len = start = end = 0;
-	else {
-		len = le16_to_cpu(ex->ee_len);
-		blk = ext4_ext_pblock(ex);
-		start = le32_to_cpu(ex->ee_block);
-		end = start + len - 1;
-		if (end >= EXT4_NDIR_BLOCKS) {
-			ret = -EOPNOTSUPP;
-			goto errout;
-		}
-	}
-
-	ext4_clear_inode_flag(inode, EXT4_INODE_EXTENTS);
-	memset(ei->i_data, 0, sizeof(ei->i_data));
-	for (i = start; i <= end; i++)
-		ei->i_data[i] = cpu_to_le32(blk++);
-	ret2 = ext4_mark_inode_dirty(handle, inode);
-	if (unlikely(ret2 && !ret))
-		ret = ret2;
-errout:
-	ext4_journal_stop(handle);
-	up_write(&EXT4_I(inode)->i_data_sem);
-out_unlock:
-	percpu_up_write(&sbi->s_writepages_rwsem);
-	return ret;
-}

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