Re: [PATCH] JBD: use GFP_NOFS in kmalloc

Andrew Morton
2007-09-19T21:35:24Z

On Wed, 19 Sep 2007 12:22:09 -0700
Mingming Cao <cmm@us.ibm.com> wrote:

> Convert the GFP_KERNEL flag used in JBD/JBD2 to GFP_NOFS, consistent
> with the rest of kmalloc flag used in the JBD/JBD2 layer.
>
> Signed-off-by: Mingming Cao <cmm@us.ibm.com>
>
> ---
> fs/jbd/journal.c | 6 +++---
> fs/jbd/revoke.c | 8 ++++----
> fs/jbd2/journal.c | 6 +++---
> fs/jbd2/revoke.c | 8 ++++----
> 4 files changed, 14 insertions(+), 14 deletions(-)
>
> Index: linux-2.6.23-rc6/fs/jbd/journal.c
> ===================================================================
> --- linux-2.6.23-rc6.orig/fs/jbd/journal.c 2007-09-19 11:51:10.000000000 -0700
> +++ linux-2.6.23-rc6/fs/jbd/journal.c 2007-09-19 11:51:57.000000000 -0700
> @@ -653,7 +653,7 @@ static journal_t * journal_init_common (
> journal_t *journal;
> int err;
>
> - journal = kmalloc(sizeof(*journal), GFP_KERNEL);
> + journal = kmalloc(sizeof(*journal), GFP_NOFS);
> if (!journal)
> goto fail;
> memset(journal, 0, sizeof(*journal));
> @@ -723,7 +723,7 @@ journal_t * journal_init_dev(struct bloc
> journal->j_blocksize = blocksize;
> n = journal->j_blocksize / sizeof(journal_block_tag_t);
> journal->j_wbufsize = n;
> - journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
> + journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_NOFS);
> if (!journal->j_wbuf) {
> printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
> __FUNCTION__);
> @@ -777,7 +777,7 @@ journal_t * journal_init_inode (struct i
> /* journal descriptor can store up to n blocks -bzzz */
> n = journal->j_blocksize / sizeof(journal_block_tag_t);
> journal->j_wbufsize = n;
> - journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_KERNEL);
> + journal->j_wbuf = kmalloc(n * sizeof(struct buffer_head*), GFP_NOFS);
> if (!journal->j_wbuf) {
> printk(KERN_ERR "%s: Cant allocate bhs for commit thread\n",
> __FUNCTION__);
> Index: linux-2.6.23-rc6/fs/jbd/revoke.c
> ===================================================================
> --- linux-2.6.23-rc6.orig/fs/jbd/revoke.c 2007-09-19 11:51:30.000000000 -0700
> +++ linux-2.6.23-rc6/fs/jbd/revoke.c 2007-09-19 11:52:34.000000000 -0700
> @@ -206,7 +206,7 @@ int journal_init_revoke(journal_t *journ
> while((tmp >>= 1UL) != 0UL)
> shift++;
>
> - journal->j_revoke_table[0] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
> + journal->j_revoke_table[0] = kmem_cache_alloc(revoke_table_cache, GFP_NOFS);
> if (!journal->j_revoke_table[0])
> return -ENOMEM;
> journal->j_revoke = journal->j_revoke_table[0];
> @@ -219,7 +219,7 @@ int journal_init_revoke(journal_t *journ
> journal->j_revoke->hash_shift = shift;
>
> journal->j_revoke->hash_table =
> - kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
> + kmalloc(hash_size * sizeof(struct list_head), GFP_NOFS);
> if (!journal->j_revoke->hash_table) {
> kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
> journal->j_revoke = NULL;
> @@ -229,7 +229,7 @@ int journal_init_revoke(journal_t *journ
> for (tmp = 0; tmp < hash_size; tmp++)
> INIT_LIST_HEAD(&journal->j_revoke->hash_table[tmp]);
>
> - journal->j_revoke_table[1] = kmem_cache_alloc(revoke_table_cache, GFP_KERNEL);
> + journal->j_revoke_table[1] = kmem_cache_alloc(revoke_table_cache, GFP_NOFS);
> if (!journal->j_revoke_table[1]) {
> kfree(journal->j_revoke_table[0]->hash_table);
> kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);
> @@ -246,7 +246,7 @@ int journal_init_revoke(journal_t *journ
> journal->j_revoke->hash_shift = shift;
>
> journal->j_revoke->hash_table =
> - kmalloc(hash_size * sizeof(struct list_head), GFP_KERNEL);
> + kmalloc(hash_size * sizeof(struct list_head), GFP_NOFS);
> if (!journal->j_revoke->hash_table) {
> kfree(journal->j_revoke_table[0]->hash_table);
> kmem_cache_free(revoke_table_cache, journal->j_revoke_table[0]);

These were all OK using GFP_KERNEL.

GFP_NOFS should only be used when the caller is holding some fs locks which
might cause a deadlock if that caller reentered the fs in ->writepage (and
maybe put_inode and such). That isn't the case in any of the above code,
which is all mount time stuff (I think).

ext3/4 should be using GFP_NOFS when the caller has a transaction open, has
a page locked, is holding i_mutex, etc.