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SubjectRe: [PATCH REVIEW] udf: Fix lock inversion between iprune_mutex and alloc_mutex
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Hi Jan,

On Thursday 14 August 2008, Jan Kara wrote:
> A memory allocation inside alloc_mutex must not recurse back
> into the filesystem itself because that leads to lock inversion
> between iprune_mutex and alloc_mutex (and thus to deadlocks - see
> traces below). Make allocations inside alloc_mutex use GFP_NOFS
> to avoid this problem.

What about moving the allocation before taking the mutex?
That way, we even reduce the lock contention and simplify the failure path.

Signed-off-by: Ingo Oeser <ioe-lkml@rameria.de>

diff --git a/fs/udf/ialloc.c b/fs/udf/ialloc.c
index eb9cfa2..76446eb 100644
--- a/fs/udf/ialloc.c
+++ b/fs/udf/ialloc.c
@@ -90,6 +90,25 @@ struct inode *udf_new_inode(struct inode *dir, int mode, int *err)
return NULL;
}

+ if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_EXTENDED_FE)) {
+ iinfo->i_efe = 1;
+ if (UDF_VERS_USE_EXTENDED_FE > sbi->s_udfrev)
+ sbi->s_udfrev = UDF_VERS_USE_EXTENDED_FE;
+ iinfo->i_ext.i_data = kzalloc(inode->i_sb->s_blocksize -
+ sizeof(struct extendedFileEntry),
+ GFP_KERNEL);
+ } else {
+ iinfo->i_efe = 0;
+ iinfo->i_ext.i_data = kzalloc(inode->i_sb->s_blocksize -
+ sizeof(struct fileEntry),
+ GFP_KERNEL);
+ }
+ if (!iinfo->i_ext.i_data) {
+ iput(inode);
+ *err = -ENOMEM;
+ return NULL;
+ }
+
mutex_lock(&sbi->s_alloc_mutex);
if (sbi->s_lvid_bh) {
struct logicalVolIntegrityDesc *lvid =
@@ -129,25 +148,6 @@ struct inode *udf_new_inode(struct inode *dir, int mode, int *err)
iinfo->i_lenEAttr = 0;
iinfo->i_lenAlloc = 0;
iinfo->i_use = 0;
- if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_EXTENDED_FE)) {
- iinfo->i_efe = 1;
- if (UDF_VERS_USE_EXTENDED_FE > sbi->s_udfrev)
- sbi->s_udfrev = UDF_VERS_USE_EXTENDED_FE;
- iinfo->i_ext.i_data = kzalloc(inode->i_sb->s_blocksize -
- sizeof(struct extendedFileEntry),
- GFP_KERNEL);
- } else {
- iinfo->i_efe = 0;
- iinfo->i_ext.i_data = kzalloc(inode->i_sb->s_blocksize -
- sizeof(struct fileEntry),
- GFP_KERNEL);
- }
- if (!iinfo->i_ext.i_data) {
- iput(inode);
- *err = -ENOMEM;
- mutex_unlock(&sbi->s_alloc_mutex);
- return NULL;
- }
if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_AD_IN_ICB))
iinfo->i_alloc_type = ICBTAG_FLAG_AD_IN_ICB;
else if (UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_USE_SHORT_AD))

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