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Date: Fri, 23 Jul 2010 17:32:22 +0200
From: Jan Kara <jack@...e.cz>
To: Ted Ts'o <tytso@....edu>
Cc: Jan Kara <jack@...e.cz>, David Rientjes <rientjes@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Andreas Dilger <adilger@....com>,
Jiri Kosina <jkosina@...e.cz>, linux-mm@...ck.org,
linux-ext4@...r.kernel.org
Subject: Re: [patch 6/6] jbd2: remove dependency on __GFP_NOFAIL
On Fri 23-07-10 11:05:43, Ted Ts'o wrote:
> Yeah, oops. Nice catches. I also hadn't done a test compile, so
> there were some missing #include's.
>
> So once more, this time with feeling...
>
> - Ted
>
> From d24408e1b50e47b21b7d2ec5857b710e9b752dc9 Mon Sep 17 00:00:00 2001
> From: Theodore Ts'o <tytso@....edu>
> Date: Fri, 23 Jul 2010 11:03:45 -0400
> Subject: [PATCH] jbd2: Remove __GFP_NOFAIL from jbd2 layer
>
> __GFP_NOFAIL is going away, so add our own retry loop. Also add
> jbd2__journal_start() and jbd2__journal_restart() which take a gfp
> mask, so that file systems can optionally (re)start transaction
> handles using GFP_KERNEL. If they do this, then they need to be
> prepared to handle receiving an PTR_ERR(-ENOMEM) error, and be ready
> to reflect that error up to userspace.
>
> Signed-off-by: "Theodore Ts'o" <tytso@....edu>
Now the patch looks good.
Acked-by: Jan Kara <jack@...e.cz>
Honza
> ---
> fs/jbd2/journal.c | 15 +++++++++--
> fs/jbd2/transaction.c | 61 +++++++++++++++++++++++++++++++++---------------
> include/linux/jbd2.h | 4 ++-
> 3 files changed, 57 insertions(+), 23 deletions(-)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index f7bf157..a79d334 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -41,6 +41,7 @@
> #include <linux/hash.h>
> #include <linux/log2.h>
> #include <linux/vmalloc.h>
> +#include <linux/backing-dev.h>
>
> #define CREATE_TRACE_POINTS
> #include <trace/events/jbd2.h>
> @@ -48,8 +49,6 @@
> #include <asm/uaccess.h>
> #include <asm/page.h>
>
> -EXPORT_SYMBOL(jbd2_journal_start);
> -EXPORT_SYMBOL(jbd2_journal_restart);
> EXPORT_SYMBOL(jbd2_journal_extend);
> EXPORT_SYMBOL(jbd2_journal_stop);
> EXPORT_SYMBOL(jbd2_journal_lock_updates);
> @@ -311,7 +310,17 @@ int jbd2_journal_write_metadata_buffer(transaction_t *transaction,
> */
> J_ASSERT_BH(bh_in, buffer_jbddirty(bh_in));
>
> - new_bh = alloc_buffer_head(GFP_NOFS|__GFP_NOFAIL);
> +retry_alloc:
> + new_bh = alloc_buffer_head(GFP_NOFS);
> + if (!new_bh) {
> + /*
> + * Failure is not an option, but __GFP_NOFAIL is going
> + * away; so we retry ourselves here.
> + */
> + congestion_wait(BLK_RW_ASYNC, HZ/50);
> + goto retry_alloc;
> + }
> +
> /* keep subsequent assertions sane */
> new_bh->b_state = 0;
> init_buffer(new_bh, NULL, NULL);
> diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
> index e214d68..001e95f 100644
> --- a/fs/jbd2/transaction.c
> +++ b/fs/jbd2/transaction.c
> @@ -26,6 +26,8 @@
> #include <linux/mm.h>
> #include <linux/highmem.h>
> #include <linux/hrtimer.h>
> +#include <linux/backing-dev.h>
> +#include <linux/module.h>
>
> static void __jbd2_journal_temp_unlink_buffer(struct journal_head *jh);
>
> @@ -83,30 +85,38 @@ jbd2_get_transaction(journal_t *journal, transaction_t *transaction)
> * transaction's buffer credits.
> */
>
> -static int start_this_handle(journal_t *journal, handle_t *handle)
> +static int start_this_handle(journal_t *journal, handle_t *handle,
> + int gfp_mask)
> {
> transaction_t *transaction;
> int needed;
> int nblocks = handle->h_buffer_credits;
> transaction_t *new_transaction = NULL;
> - int ret = 0;
> unsigned long ts = jiffies;
>
> if (nblocks > journal->j_max_transaction_buffers) {
> printk(KERN_ERR "JBD: %s wants too many credits (%d > %d)\n",
> current->comm, nblocks,
> journal->j_max_transaction_buffers);
> - ret = -ENOSPC;
> - goto out;
> + return -ENOSPC;
> }
>
> alloc_transaction:
> if (!journal->j_running_transaction) {
> - new_transaction = kzalloc(sizeof(*new_transaction),
> - GFP_NOFS|__GFP_NOFAIL);
> + new_transaction = kzalloc(sizeof(*new_transaction), gfp_mask);
> if (!new_transaction) {
> - ret = -ENOMEM;
> - goto out;
> + /*
> + * If __GFP_FS is not present, then we may be
> + * being called from inside the fs writeback
> + * layer, so we MUST NOT fail. Since
> + * __GFP_NOFAIL is going away, we will arrange
> + * to retry the allocation ourselves.
> + */
> + if ((gfp_mask & __GFP_FS) == 0) {
> + congestion_wait(BLK_RW_ASYNC, HZ/50);
> + goto alloc_transaction;
> + }
> + return -ENOMEM;
> }
> }
>
> @@ -123,8 +133,8 @@ repeat_locked:
> if (is_journal_aborted(journal) ||
> (journal->j_errno != 0 && !(journal->j_flags & JBD2_ACK_ERR))) {
> spin_unlock(&journal->j_state_lock);
> - ret = -EROFS;
> - goto out;
> + kfree(new_transaction);
> + return -EROFS;
> }
>
> /* Wait on the journal's transaction barrier if necessary */
> @@ -240,10 +250,8 @@ repeat_locked:
> spin_unlock(&journal->j_state_lock);
>
> lock_map_acquire(&handle->h_lockdep_map);
> -out:
> - if (unlikely(new_transaction)) /* It's usually NULL */
> - kfree(new_transaction);
> - return ret;
> + kfree(new_transaction);
> + return 0;
> }
>
> static struct lock_class_key jbd2_handle_key;
> @@ -278,7 +286,7 @@ static handle_t *new_handle(int nblocks)
> *
> * Return a pointer to a newly allocated handle, or NULL on failure
> */
> -handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
> +handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int gfp_mask)
> {
> handle_t *handle = journal_current_handle();
> int err;
> @@ -298,7 +306,7 @@ handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
>
> current->journal_info = handle;
>
> - err = start_this_handle(journal, handle);
> + err = start_this_handle(journal, handle, gfp_mask);
> if (err < 0) {
> jbd2_free_handle(handle);
> current->journal_info = NULL;
> @@ -308,6 +316,15 @@ handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
> out:
> return handle;
> }
> +EXPORT_SYMBOL(jbd2__journal_start);
> +
> +
> +handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
> +{
> + return jbd2__journal_start(journal, nblocks, GFP_NOFS);
> +}
> +EXPORT_SYMBOL(jbd2_journal_start);
> +
>
> /**
> * int jbd2_journal_extend() - extend buffer credits.
> @@ -394,8 +411,7 @@ out:
> * transaction capabable of guaranteeing the requested number of
> * credits.
> */
> -
> -int jbd2_journal_restart(handle_t *handle, int nblocks)
> +int jbd2__journal_restart(handle_t *handle, int nblocks, int gfp_mask)
> {
> transaction_t *transaction = handle->h_transaction;
> journal_t *journal = transaction->t_journal;
> @@ -428,10 +444,17 @@ int jbd2_journal_restart(handle_t *handle, int nblocks)
>
> lock_map_release(&handle->h_lockdep_map);
> handle->h_buffer_credits = nblocks;
> - ret = start_this_handle(journal, handle);
> + ret = start_this_handle(journal, handle, gfp_mask);
> return ret;
> }
> +EXPORT_SYMBOL(jbd2__journal_restart);
> +
>
> +int jbd2_journal_restart(handle_t *handle, int nblocks)
> +{
> + return jbd2__journal_restart(handle, nblocks, GFP_NOFS);
> +}
> +EXPORT_SYMBOL(jbd2_journal_restart);
>
> /**
> * void jbd2_journal_lock_updates () - establish a transaction barrier.
> diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
> index a4d2e9f..5a72bc7 100644
> --- a/include/linux/jbd2.h
> +++ b/include/linux/jbd2.h
> @@ -1081,7 +1081,9 @@ static inline handle_t *journal_current_handle(void)
> */
>
> extern handle_t *jbd2_journal_start(journal_t *, int nblocks);
> -extern int jbd2_journal_restart (handle_t *, int nblocks);
> +extern handle_t *jbd2__journal_start(journal_t *, int nblocks, int gfp_mask);
> +extern int jbd2_journal_restart(handle_t *, int nblocks);
> +extern int jbd2__journal_restart(handle_t *, int nblocks, int gfp_mask);
> extern int jbd2_journal_extend (handle_t *, int nblocks);
> extern int jbd2_journal_get_write_access(handle_t *, struct buffer_head *);
> extern int jbd2_journal_get_create_access (handle_t *, struct buffer_head *);
> --
> 1.7.0.4
>
--
Jan Kara <jack@...e.cz>
SUSE Labs, CR
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