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Date: Mon, 23 May 2011 18:41:23 +0200
From: Jan Kara <jack@...e.cz>
To: Manish Katiyar <mkatiyar@...il.com>
Cc: Jan Kara <jack@...e.cz>, ext4 <linux-ext4@...r.kernel.org>,
Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 2/5] ext4 : Update low level ext4 journal routines to
specify gfp_mask for transaction allocation.
On Sat 21-05-11 19:43:10, Manish Katiyar wrote:
> On Wed, May 11, 2011 at 9:04 AM, Jan Kara <jack@...e.cz> wrote:
> > On Sun 24-04-11 17:13:18, Manish Katiyar wrote:
> >> Update low level ext4 journal routines to pass an extra parameter
> >> to journal allocation routines to specify whether transaction allocation
> >> can fail or not. With this patch ext4_journal_start() can fail due to
> >> ENOMEM. Added a new interface ext4_journal_start_tryhard() which isn't
> >> supposed to fail and keep retrying till the allocation succeeds.
> > As I wrote in a comment in the comment to the first patch, first just
> > make ext4_journal_start_sb() and similar functions pass false as a part of
> > the first patch.
> >
> > Then it would be better to create a new function that passes true - the
> > name does not really matter since it will be removed later in the series
> > but it will help the review process. You can call it
> > ext4_journal_start_sb_enomem() or whatever. This way we keep backward
> > compatibility because currently all call sites really expect the retry
> > behavior.
>
> Hi Jan,
>
> Here is the updated patch incorporating your comments. This adds a new
> function ext4_journal_start_failok and updates the ext4 code where we
> can fail.
>
> This patch adds a new wrapper ext4_journal_start_failok() which
> can fail with -ENOMEM. Update the ext4 code with this, where callers
> are ok failing the transaction start.
Thanks. My comments are below.
> Signed-off-by: Manish Katiyar <mkatiyar@...il.com>
> ---
> fs/ext4/acl.c | 6 +++---
> fs/ext4/ext4_jbd2.h | 10 +++++++++-
> fs/ext4/extents.c | 2 +-
> fs/ext4/inode.c | 19 +++++++++++--------
> fs/ext4/ioctl.c | 4 ++--
> fs/ext4/migrate.c | 4 ++--
> fs/ext4/move_extent.c | 2 +-
> fs/ext4/namei.c | 23 +++++++++++++++--------
> fs/ext4/super.c | 17 ++++++++++++++---
> fs/ext4/xattr.c | 3 ++-
> fs/jbd2/transaction.c | 4 +++-
> 11 files changed, 63 insertions(+), 31 deletions(-)
>
> diff --git a/fs/ext4/acl.c b/fs/ext4/acl.c
> index 21eacd7..cdb1f51 100644
> --- a/fs/ext4/acl.c
> +++ b/fs/ext4/acl.c
> @@ -350,11 +350,10 @@ ext4_acl_chmod(struct inode *inode)
> int retries = 0;
>
> retry:
> - handle = ext4_journal_start(inode,
> + handle = ext4_journal_start_failok(inode,
> EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
> if (IS_ERR(handle)) {
> error = PTR_ERR(handle);
> - ext4_std_error(inode->i_sb, error);
Here, you should rather do
if (error != ENOMEM)
ext4_std_error(inode->i_sb, error);
We probably want to know about EIO (which is the other realistic error).
> @@ -449,7 +448,8 @@ ext4_xattr_set_acl(struct dentry *dentry, const
> char *name, const void *value,
> acl = NULL;
>
> retry:
> - handle = ext4_journal_start(inode, EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
> + handle = ext4_journal_start_failok(inode,
> + EXT4_DATA_TRANS_BLOCKS(inode->i_sb));
> if (IS_ERR(handle))
> return PTR_ERR(handle);
> error = ext4_set_acl(handle, inode, type, acl);
This change is OK. But looking at the code there, we should rather do
if (IS_ERR(handle)) {
error = PTR_ERR(handle);
goto release_and_out;
}
Can you please include this change in your other patch fixing ACL error
handling? Thanks.
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index f2fa5e8..f7b2d4d 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -3523,7 +3523,7 @@ retry:
> int err;
>
> /* Credits for sb + inode write */
> - handle = ext4_journal_start(inode, 2);
> + handle = ext4_journal_start_failok(inode, 2);
> if (IS_ERR(handle)) {
> /* This is really bad luck. We've written the data
> * but cannot extend i_size. Bail out and pretend
Here we shouldn't fail because that will leave blocks outside EOF
allocated. So just leave there original ext4_journal_start().
> @@ -5371,7 +5372,9 @@ int ext4_setattr(struct dentry *dentry, struct
> iattr *attr)
> rc = ext4_acl_chmod(inode);
>
> err_out:
> - ext4_std_error(inode->i_sb, error);
> + if (error != -ENOMEM) {
> + ext4_std_error(inode->i_sb, error);
> + }
No need for braces here...
> diff --git a/fs/ext4/migrate.c b/fs/ext4/migrate.c
> index 92816b4..8870746 100644
> --- a/fs/ext4/migrate.c
> +++ b/fs/ext4/migrate.c
> @@ -533,7 +533,7 @@ int ext4_ext_migrate(struct inode *inode)
> ext4_set_inode_state(inode, EXT4_STATE_EXT_MIGRATE);
> up_read((&EXT4_I(inode)->i_data_sem));
>
> - handle = ext4_journal_start(inode, 1);
> + handle = ext4_journal_start_failok(inode, 1);
> if (IS_ERR(handle)) {
> /*
> * It is impossible to update on-disk structures without
Here we should better not fail because we have inode on orphan list and
need to eventually remove it. So just keep old ext4_journal_start().
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 4e4c17f..2d57a57 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -247,7 +247,8 @@ static void ext4_put_nojournal(handle_t *handle)
> * ext4 prevents a new handle from being started by s_frozen, which
> * is in an upper layer.
> */
> -handle_t *ext4_journal_start_sb(struct super_block *sb, int nblocks)
> +static handle_t *ext4_journal_start_sb_int(struct super_block *sb,
> + int nblocks, bool errok)
Maybe __ext4_journal_start_sb() would be a more usual name...
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index b5c2550..3453c29 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -308,6 +308,8 @@ static handle_t *new_handle(int nblocks)
> * handle_t *jbd2_journal_start() - Obtain a new handle.
> * @journal: Journal to start transaction on.
> * @nblocks: number of block buffer we might modify
> + * @errok : True if the transaction allocation can fail
> + * with ENOMEM.
> *
> * We make sure that the transaction can guarantee at least nblocks of
> * modified buffers in the log. We block until the log can guarantee
Move this to the patch adding the parameter...
> @@ -338,7 +340,7 @@ handle_t *jbd2_journal_start(journal_t *journal,
> int nblocks, bool errok)
>
> current->journal_info = handle;
>
> - err = start_this_handle(journal, handle, GFP_NOFS);
> + err = start_this_handle(journal, handle, errok ? GFP_KERNEL : GFP_NOFS);
> if (err < 0) {
> jbd2_free_handle(handle);
> current->journal_info = NULL;
This is probably just a leftover from some previous version?
Honza
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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