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bcachefs: Journal reclaim requires memalloc_noreclaim_save()

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Memory reclaim requires journal reclaim to make forward progress - it's
what cleans our caches - thus, while we're in journal reclaim or holding
the journal reclaim lock we can't recurse into  memory reclaim.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
This commit is contained in:
Kent Overstreet 2020-11-19 21:15:39 -05:00 committed by Kent Overstreet
parent b3c2a06b7d
commit 9d4582ffdb
1 changed files with 12 additions and 0 deletions
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12
fs/bcachefs/journal_reclaim.c
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@ -9,6 +9,8 @@
#include "super.h"
#include "trace.h"
#include <linux/sched/mm.h>
/* Free space calculations: */
static unsigned journal_space_from(struct journal_device *ja,
@ -537,8 +539,16 @@ void bch2_journal_reclaim(struct journal *j)
struct bch_fs *c = container_of(j, struct bch_fs, journal);
u64 seq_to_flush, nr_flushed = 0;
size_t min_nr;
unsigned flags;
/*
* We can't invoke memory reclaim while holding the reclaim_lock -
* journal reclaim is required to make progress for memory reclaim
* (cleaning the caches), so we can't get stuck in memory reclaim while
* we're holding the reclaim lock:
*/
lockdep_assert_held(&j->reclaim_lock);
flags = memalloc_noreclaim_save();
do {
bch2_journal_do_discards(j);
@ -575,6 +585,8 @@ void bch2_journal_reclaim(struct journal *j)
nr_flushed += journal_flush_pins(j, seq_to_flush, min_nr);
} while (min_nr);
memalloc_noreclaim_restore(flags);
trace_journal_reclaim_finish(c, nr_flushed);
if (!bch2_journal_error(j))