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authorKent Overstreet2024-01-15 20:37:23 -0500
committerKent Overstreet2024-01-21 13:27:10 -0500
commit46bf2e9cc745996ca56e56ed816e60d07811bd9a (patch)
tree94858ccb5646f0629924d68761471e24b67433df /fs
parent1a5039041b376f545dfc11d89af77cc720217b44 (diff)
bcachefs: Fix excess transaction restarts in __bchfs_fallocate()
drop_locks_do() should not be used in a fastpath without first trying the do in nonblocking mode - the unlock and relock will cause excessive transaction restarts and potentially livelocking with other threads that are contending for the same locks. Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Diffstat (limited to 'fs')
-rw-r--r--fs/bcachefs/btree_iter.h5
-rw-r--r--fs/bcachefs/fs-io-pagecache.c37
-rw-r--r--fs/bcachefs/fs-io-pagecache.h2
-rw-r--r--fs/bcachefs/fs-io.c7
4 files changed, 35 insertions, 16 deletions
diff --git a/fs/bcachefs/btree_iter.h b/fs/bcachefs/btree_iter.h
index da2b74fa63fc..24772538e4cc 100644
--- a/fs/bcachefs/btree_iter.h
+++ b/fs/bcachefs/btree_iter.h
@@ -819,6 +819,11 @@ __bch2_btree_iter_peek_and_restart(struct btree_trans *trans,
#define for_each_btree_key_continue_norestart(_iter, _flags, _k, _ret) \
for_each_btree_key_upto_continue_norestart(_iter, SPOS_MAX, _flags, _k, _ret)
+/*
+ * This should not be used in a fastpath, without first trying _do in
+ * nonblocking mode - it will cause excessive transaction restarts and
+ * potentially livelocking:
+ */
#define drop_locks_do(_trans, _do) \
({ \
bch2_trans_unlock(_trans); \
diff --git a/fs/bcachefs/fs-io-pagecache.c b/fs/bcachefs/fs-io-pagecache.c
index ff664fd0d8ef..d359aa9b33b8 100644
--- a/fs/bcachefs/fs-io-pagecache.c
+++ b/fs/bcachefs/fs-io-pagecache.c
@@ -309,39 +309,49 @@ void bch2_mark_pagecache_unallocated(struct bch_inode_info *inode,
}
}
-void bch2_mark_pagecache_reserved(struct bch_inode_info *inode,
- u64 start, u64 end)
+int bch2_mark_pagecache_reserved(struct bch_inode_info *inode,
+ u64 *start, u64 end,
+ bool nonblocking)
{
struct bch_fs *c = inode->v.i_sb->s_fs_info;
- pgoff_t index = start >> PAGE_SECTORS_SHIFT;
+ pgoff_t index = *start >> PAGE_SECTORS_SHIFT;
pgoff_t end_index = (end - 1) >> PAGE_SECTORS_SHIFT;
struct folio_batch fbatch;
s64 i_sectors_delta = 0;
- unsigned i, j;
+ int ret = 0;
- if (end <= start)
- return;
+ if (end <= *start)
+ return 0;
folio_batch_init(&fbatch);
while (filemap_get_folios(inode->v.i_mapping,
&index, end_index, &fbatch)) {
- for (i = 0; i < folio_batch_count(&fbatch); i++) {
+ for (unsigned i = 0; i < folio_batch_count(&fbatch); i++) {
struct folio *folio = fbatch.folios[i];
+
+ if (!nonblocking)
+ folio_lock(folio);
+ else if (!folio_trylock(folio)) {
+ folio_batch_release(&fbatch);
+ ret = -EAGAIN;
+ break;
+ }
+
u64 folio_start = folio_sector(folio);
u64 folio_end = folio_end_sector(folio);
- unsigned folio_offset = max(start, folio_start) - folio_start;
- unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;
- struct bch_folio *s;
BUG_ON(end <= folio_start);
- folio_lock(folio);
- s = bch2_folio(folio);
+ *start = min(end, folio_end);
+ struct bch_folio *s = bch2_folio(folio);
if (s) {
+ unsigned folio_offset = max(*start, folio_start) - folio_start;
+ unsigned folio_len = min(end, folio_end) - folio_offset - folio_start;
+
spin_lock(&s->lock);
- for (j = folio_offset; j < folio_offset + folio_len; j++) {
+ for (unsigned j = folio_offset; j < folio_offset + folio_len; j++) {
i_sectors_delta -= s->s[j].state == SECTOR_dirty;
bch2_folio_sector_set(folio, s, j,
folio_sector_reserve(s->s[j].state));
@@ -356,6 +366,7 @@ void bch2_mark_pagecache_reserved(struct bch_inode_info *inode,
}
bch2_i_sectors_acct(c, inode, NULL, i_sectors_delta);
+ return ret;
}
static inline unsigned sectors_to_reserve(struct bch_folio_sector *s,
diff --git a/fs/bcachefs/fs-io-pagecache.h b/fs/bcachefs/fs-io-pagecache.h
index 27f712ae37a6..8cbaba6565b4 100644
--- a/fs/bcachefs/fs-io-pagecache.h
+++ b/fs/bcachefs/fs-io-pagecache.h
@@ -143,7 +143,7 @@ int bch2_folio_set(struct bch_fs *, subvol_inum, struct folio **, unsigned);
void bch2_bio_page_state_set(struct bio *, struct bkey_s_c);
void bch2_mark_pagecache_unallocated(struct bch_inode_info *, u64, u64);
-void bch2_mark_pagecache_reserved(struct bch_inode_info *, u64, u64);
+int bch2_mark_pagecache_reserved(struct bch_inode_info *, u64 *, u64, bool);
int bch2_get_folio_disk_reservation(struct bch_fs *,
struct bch_inode_info *,
diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
index 98bd5babab19..dc52918d06ef 100644
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -675,8 +675,11 @@ static int __bchfs_fallocate(struct bch_inode_info *inode, int mode,
bch2_i_sectors_acct(c, inode, &quota_res, i_sectors_delta);
- drop_locks_do(trans,
- (bch2_mark_pagecache_reserved(inode, hole_start, iter.pos.offset), 0));
+ if (bch2_mark_pagecache_reserved(inode, &hole_start,
+ iter.pos.offset, true))
+ drop_locks_do(trans,
+ bch2_mark_pagecache_reserved(inode, &hole_start,
+ iter.pos.offset, false));
bkey_err:
bch2_quota_reservation_put(c, inode, &quota_res);
if (bch2_err_matches(ret, BCH_ERR_transaction_restart))