Messages in this thread Patch in this message | | | Subject | [patch, 2.6.17-rc5-mm3] Lockdep: Annotate the quota code | From | Arjan van de Ven <> | Date | Tue, 06 Jun 2006 20:55:20 +0200 |
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Hi,
The quota code plays interesting games with the lock ordering; to quote Jan:
| i_mutex of inode containing quota file is acquired after all other | quota locks. i_mutex of all other inodes is acquired before quota | locks. Quota code makes sure (by resetting inode operations and | setting special flag on inode) that noone tries to enter quota code | while holding i_mutex on a quota file...
The good news is that all of this special case i_mutex grabbing happens in the (per filesystem) low level quota write function. For this special case we need a new I_MUTEX_* nesting level, since this just entirely outside any of the regular VFS locking rules for i_mutex. I trust Jan on his blue eyes that this is not ever going to deadlock; and based on that the patch below is what it takes to inform lockdep of these very interesting new locking rules.
The new locking rule for the I_MUTEX_QUOTA nesting level is that this is the deepest possible level of nesting for i_mutex, and that this only should be used in quota write (and possibly read) function of filesystems. This makes the lock ordering of the I_MUTEX_* levels:
I_MUTEX_PARENT -> I_MUTEX_CHILD -> I_MUTEX_NORMAL -> I_MUTEX_QUOTA
Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Acked-by: Ingo Molnar <mingo@elte.hu>
--- fs/dquot.c | 2 +- fs/ext2/super.c | 2 +- fs/ext3/super.c | 2 +- fs/reiserfs/super.c | 2 +- fs/ufs/super.c | 2 +- include/linux/fs.h | 7 ++++++- 6 files changed, 11 insertions(+), 6 deletions(-)
Index: linux-2.6.17-rc5-mm3/fs/dquot.c =================================================================== --- linux-2.6.17-rc5-mm3.orig/fs/dquot.c +++ linux-2.6.17-rc5-mm3/fs/dquot.c @@ -1475,7 +1475,7 @@ static int vfs_quota_on_inode(struct ino goto out_file_init; } mutex_unlock(&dqopt->dqio_mutex); - mutex_unlock(&inode->i_mutex); + mutex_unlock_non_nested(&inode->i_mutex); set_enable_flags(dqopt, type); add_dquot_ref(sb, type); Index: linux-2.6.17-rc5-mm3/fs/ext2/super.c =================================================================== --- linux-2.6.17-rc5-mm3.orig/fs/ext2/super.c +++ linux-2.6.17-rc5-mm3/fs/ext2/super.c @@ -1157,7 +1157,7 @@ static ssize_t ext2_quota_write(struct s struct buffer_head tmp_bh; struct buffer_head *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; Index: linux-2.6.17-rc5-mm3/fs/ext3/super.c =================================================================== --- linux-2.6.17-rc5-mm3.orig/fs/ext3/super.c +++ linux-2.6.17-rc5-mm3/fs/ext3/super.c @@ -2614,7 +2614,7 @@ static ssize_t ext3_quota_write(struct s struct buffer_head *bh; handle_t *handle = journal_current_handle(); - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; Index: linux-2.6.17-rc5-mm3/fs/reiserfs/super.c =================================================================== --- linux-2.6.17-rc5-mm3.orig/fs/reiserfs/super.c +++ linux-2.6.17-rc5-mm3/fs/reiserfs/super.c @@ -2204,7 +2204,7 @@ static ssize_t reiserfs_quota_write(stru size_t towrite = len; struct buffer_head tmp_bh, *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; Index: linux-2.6.17-rc5-mm3/fs/ufs/super.c =================================================================== --- linux-2.6.17-rc5-mm3.orig/fs/ufs/super.c +++ linux-2.6.17-rc5-mm3/fs/ufs/super.c @@ -1269,7 +1269,7 @@ static ssize_t ufs_quota_write(struct su size_t towrite = len; struct buffer_head *bh; - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA); while (towrite > 0) { tocopy = sb->s_blocksize - offset < towrite ? sb->s_blocksize - offset : towrite; Index: linux-2.6.17-rc5-mm3/include/linux/fs.h =================================================================== --- linux-2.6.17-rc5-mm3.orig/include/linux/fs.h +++ linux-2.6.17-rc5-mm3/include/linux/fs.h @@ -563,12 +563,17 @@ struct inode { * 0: the object of the current VFS operation * 1: parent * 2: child/target + * 3: quota file + * + * The locking order between these types is + * parent -> child -> normal -> quota */ enum inode_i_mutex_lock_type { I_MUTEX_NORMAL, I_MUTEX_PARENT, - I_MUTEX_CHILD + I_MUTEX_CHILD, + I_MUTEX_QUOTA }; /* - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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