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Date: Thu, 5 Nov 2009 14:55:21 +0100 From: Jan Kara <jack@...e.cz> To: Jan Blunck <jblunck@...e.de> Cc: Andi Kleen <andi@...stfloor.org>, linux-fsdevel@...r.kernel.org, Matthew Wilcox <matthew@....cx>, linux-kernel@...r.kernel.org, Jan Kara <jack@...e.cz>, Al Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, Andi Kleen <ak@...ux.intel.com>, Christoph Hellwig <hch@....de>, Pekka Enberg <penberg@...helsinki.fi>, Andreas Dilger <adilger@....com>, linux-ext4@...r.kernel.org Subject: Re: [PATCH 04/27] ext2: Add ext2_sb_info mutex On Mon 02-11-09 17:57:52, Jan Blunck wrote: > On Mon, Nov 02, Andi Kleen wrote: > > > > @@ -762,6 +767,12 @@ static int ext2_fill_super(struct super_block *sb, void *data, int silent) > > > sbi->s_sb_block = sb_block; > > > > > > /* > > > + * mutex for protection of modifications of the superblock while being > > > + * write out by ext2_write_super() or ext2_sync_fs(). > > > + */ > > > + mutex_init(&sbi->s_mutex); > > > > I didn't go over all the code paths in detail, but if you replace > > the BKL with a mutex that is hold over a longer write-out sleep > > period you potentially limit IO parallelism a lot. > > Right. I converted it to be a spinlock and unlock before calling > ext2_sync_super(). > > What do you think? The patch is generally fine. I have just a few minor comments below: > diff --git a/fs/ext2/super.c b/fs/ext2/super.c > index 5af1775..70c326c 100644 > --- a/fs/ext2/super.c > +++ b/fs/ext2/super.c > @@ -52,8 +52,10 @@ void ext2_error (struct super_block * sb, const char * function, > struct ext2_super_block *es = sbi->s_es; > > if (!(sb->s_flags & MS_RDONLY)) { > + spin_lock(&sbi->s_lock); > sbi->s_mount_state |= EXT2_ERROR_FS; > es->s_state |= cpu_to_le16(EXT2_ERROR_FS); > + /* drops sbi->s_lock */ > ext2_sync_super(sb, es); I don't like this dropping of spinlock inside ext2_sync_super. Can we just drop it here and retake it in ext2_sync_super? It's by far not a performance critical path so it should not really matter. > diff --git a/include/linux/ext2_fs_sb.h b/include/linux/ext2_fs_sb.h > index 1cdb663..0d20278 100644 > --- a/include/linux/ext2_fs_sb.h > +++ b/include/linux/ext2_fs_sb.h > @@ -106,6 +106,8 @@ struct ext2_sb_info { > spinlock_t s_rsv_window_lock; > struct rb_root s_rsv_window_root; > struct ext2_reserve_window_node s_rsv_window_head; > + /* protect against concurrent modifications of this structure */ > + spinlock_t s_lock; > }; As I'm reading the code s_lock protects some of the fieds but definitely not all. I'd say it protects s_mount_state, s_blocks_last, s_overhead_last, and a content of superblock's buffer pointed to by sbi->s_es. The rest just either does not change during lifetime of the filesystem or has different locks (either s_umount semaphore or other spinlocks). Honza -- Jan Kara <jack@...e.cz> SUSE Labs, CR -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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