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authorZhang Yi <yi.zhang@huawei.com>2022-09-01 21:34:53 +0800
committerAndrew Morton <akpm@linux-foundation.org>2022-09-11 20:26:06 -0700
commitfdee117ee86479fd2644bcd9ac2b2469e55722d1 (patch)
treea2a4e97bd7dbba96807d47d3f080e7a99281cf6d /fs/buffer.c
parent214f8796907b8015b778badf4710a4701472779a (diff)
fs/buffer: add some new buffer read helpers
Current ll_rw_block() helper is fragile because it assumes that locked buffer means it's under IO which is submitted by some other who holds the lock, it skip buffer if it failed to get the lock, so it's only safe on the readahead path. Unfortunately, now that most filesystems still use this helper mistakenly on the sync metadata read path. There is no guarantee that the one who holds the buffer lock always submit IO (e.g. buffer_migrate_folio_norefs() after commit 88dbcbb3a484 ("blkdev: avoid migration stalls for blkdev pages"), it could lead to false positive -EIO when submitting reading IO. This patch add some friendly buffer read helpers to prepare replacing ll_rw_block() and similar calls. We can only call bh_readahead_[] helpers for the readahead paths. Link: https://lkml.kernel.org/r/20220901133505.2510834-3-yi.zhang@huawei.com Signed-off-by: Zhang Yi <yi.zhang@huawei.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/buffer.c')
-rw-r--r--fs/buffer.c65
1 files changed, 65 insertions, 0 deletions
diff --git a/fs/buffer.c b/fs/buffer.c
index a0b70b3239f3..a6bc769e665d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -3018,6 +3018,71 @@ int bh_uptodate_or_lock(struct buffer_head *bh)
EXPORT_SYMBOL(bh_uptodate_or_lock);
/**
+ * __bh_read - Submit read for a locked buffer
+ * @bh: struct buffer_head
+ * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
+ * @wait: wait until reading finish
+ *
+ * Returns zero on success or don't wait, and -EIO on error.
+ */
+int __bh_read(struct buffer_head *bh, blk_opf_t op_flags, bool wait)
+{
+ int ret = 0;
+
+ BUG_ON(!buffer_locked(bh));
+
+ get_bh(bh);
+ bh->b_end_io = end_buffer_read_sync;
+ submit_bh(REQ_OP_READ | op_flags, bh);
+ if (wait) {
+ wait_on_buffer(bh);
+ if (!buffer_uptodate(bh))
+ ret = -EIO;
+ }
+ return ret;
+}
+EXPORT_SYMBOL(__bh_read);
+
+/**
+ * __bh_read_batch - Submit read for a batch of unlocked buffers
+ * @nr: entry number of the buffer batch
+ * @bhs: a batch of struct buffer_head
+ * @op_flags: appending REQ_OP_* flags besides REQ_OP_READ
+ * @force_lock: force to get a lock on the buffer if set, otherwise drops any
+ * buffer that cannot lock.
+ *
+ * Returns zero on success or don't wait, and -EIO on error.
+ */
+void __bh_read_batch(int nr, struct buffer_head *bhs[],
+ blk_opf_t op_flags, bool force_lock)
+{
+ int i;
+
+ for (i = 0; i < nr; i++) {
+ struct buffer_head *bh = bhs[i];
+
+ if (buffer_uptodate(bh))
+ continue;
+
+ if (force_lock)
+ lock_buffer(bh);
+ else
+ if (!trylock_buffer(bh))
+ continue;
+
+ if (buffer_uptodate(bh)) {
+ unlock_buffer(bh);
+ continue;
+ }
+
+ bh->b_end_io = end_buffer_read_sync;
+ get_bh(bh);
+ submit_bh(REQ_OP_READ | op_flags, bh);
+ }
+}
+EXPORT_SYMBOL(__bh_read_batch);
+
+/**
* bh_submit_read - Submit a locked buffer for reading
* @bh: struct buffer_head
*