From: Michal Hocko <mhocko@xxxxxxxx>
Subject: jbd2: mark the transaction context with the scope GFP_NOFS context
now that we have memalloc_nofs_{save,restore} api we can mark the whole
transaction context as implicitly GFP_NOFS. All allocations will
automatically inherit GFP_NOFS this way. This means that we do not have
to mark any of those requests with GFP_NOFS and moreover all the
ext4_kv[mz]alloc(GFP_NOFS) are also safe now because even the hardcoded
GFP_KERNEL allocations deep inside the vmalloc will be NOFS now.
[akpm@xxxxxxxxxxxxxxxxxxxx: tweak comments]
Link: http://lkml.kernel.org/r/20170306131408.9828-7-mhocko@xxxxxxxxxx
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Cc: Chris Mason <clm@xxxxxx>
Cc: David Sterba <dsterba@xxxxxxx>
Cc: Brian Foster <bfoster@xxxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Nikolay Borisov <nborisov@xxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/jbd2/transaction.c | 12 ++++++++++++
include/linux/jbd2.h | 2 ++
2 files changed, 14 insertions(+)
diff -puN fs/jbd2/transaction.c~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context fs/jbd2/transaction.c
--- a/fs/jbd2/transaction.c~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context
+++ a/fs/jbd2/transaction.c
@@ -29,6 +29,7 @@
#include <linux/backing-dev.h>
#include <linux/bug.h>
#include <linux/module.h>
+#include <linux/sched/mm.h>
#include <trace/events/jbd2.h>
@@ -388,6 +389,11 @@ repeat:
rwsem_acquire_read(&journal->j_trans_commit_map, 0, 0, _THIS_IP_);
jbd2_journal_free_transaction(new_transaction);
+ /*
+ * Ensure that no allocations done while the transaction is open are
+ * going to recurse back to the fs layer.
+ */
+ handle->saved_alloc_context = memalloc_nofs_save();
return 0;
}
@@ -466,6 +472,7 @@ handle_t *jbd2__journal_start(journal_t
trace_jbd2_handle_start(journal->j_fs_dev->bd_dev,
handle->h_transaction->t_tid, type,
line_no, nblocks);
+
return handle;
}
EXPORT_SYMBOL(jbd2__journal_start);
@@ -1760,6 +1767,11 @@ int jbd2_journal_stop(handle_t *handle)
if (handle->h_rsv_handle)
jbd2_journal_free_reserved(handle->h_rsv_handle);
free_and_exit:
+ /*
+ * Scope of the GFP_NOFS context is over here and so we can restore the
+ * original alloc context.
+ */
+ memalloc_nofs_restore(handle->saved_alloc_context);
jbd2_free_handle(handle);
return err;
}
diff -puN include/linux/jbd2.h~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context include/linux/jbd2.h
--- a/include/linux/jbd2.h~jbd2-mark-the-transaction-context-with-the-scope-gfp_nofs-context
+++ a/include/linux/jbd2.h
@@ -491,6 +491,8 @@ struct jbd2_journal_handle
unsigned long h_start_jiffies;
unsigned int h_requested_credits;
+
+ unsigned int saved_alloc_context;
};
_
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
