{"id":2215744,"url":"http://patchwork.ozlabs.org/api/patches/2215744/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-ext4/patch/20260325093349.630193-2-diangangli@gmail.com/","project":{"id":8,"url":"http://patchwork.ozlabs.org/api/projects/8/?format=json","name":"Linux ext4 filesystem development","link_name":"linux-ext4","list_id":"linux-ext4.vger.kernel.org","list_email":"linux-ext4@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20260325093349.630193-2-diangangli@gmail.com>","list_archive_url":null,"date":"2026-03-25T09:33:49","name":"[RFC,1/1] ext4: fail fast on repeated metadata reads after IO failure","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"006feecb6c5f31c0d8f1a942abe294d512ffb9f6","submitter":{"id":92966,"url":"http://patchwork.ozlabs.org/api/people/92966/?format=json","name":"Diangang Li","email":"diangangli@gmail.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/linux-ext4/patch/20260325093349.630193-2-diangangli@gmail.com/mbox/","series":[{"id":497401,"url":"http://patchwork.ozlabs.org/api/series/497401/?format=json","web_url":"http://patchwork.ozlabs.org/project/linux-ext4/list/?series=497401","date":"2026-03-25T09:33:49","name":"ext4: fail fast on repeated metadata reads after IO failure","version":1,"mbox":"http://patchwork.ozlabs.org/series/497401/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/2215744/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/2215744/checks/","tags":{},"related":[],"headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-ext4@vger.kernel.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","patchwork-incoming@ozlabs.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=gmail.com header.i=@gmail.com header.a=rsa-sha256\n header.s=20251104 header.b=jrSRf3WT;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=2404:9400:2221:ea00::3; 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If the read fails,\nthe buffer remains !Uptodate. With concurrent callers, each waiter can\nretry the same failing read after the previous holder drops BH_Lock. This\namplifies device retry latency and may trigger hung tasks.\n\nIn the normal read path the block driver already performs its own retries.\nOnce the retries keep failing, re-submitting the same metadata read from\nthe filesystem just amplifies the latency by serializing waiters on\nBH_Lock.\n\nRemember read failures on buffer_head and fail fast for ext4 metadata reads\nonce a buffer has already failed to read. Clear the flag on successful\nread/write completion so the buffer can recover. ext4 read-ahead uses\next4_read_bh_nowait(), so it does not set the failure flag and remains\nbest-effort.\n\nExample hung stacks:\n\n INFO: task toutiao.infra.t:3760933 blocked for more than 327 seconds.\n Call Trace:\n __schedule\n io_schedule\n __wait_on_bit_lock\n bh_uptodate_or_lock\n __read_extent_tree_block\n ext4_find_extent\n ext4_ext_map_blocks\n ext4_map_blocks\n ext4_getblk\n ext4_bread\n __ext4_read_dirblock\n dx_probe\n ext4_htree_fill_tree\n ext4_readdir\n iterate_dir\n ksys_getdents64\n\n INFO: task toutiao.infra.t:2724456 blocked for more than 327 seconds.\n Call Trace:\n __schedule\n io_schedule\n __wait_on_bit_lock\n ext4_read_bh_lock\n ext4_bread\n __ext4_read_dirblock\n htree_dirblock_to_tree\n ext4_htree_fill_tree\n ext4_readdir\n iterate_dir\n ksys_getdents64\n\nSigned-off-by: Diangang Li \nReviewed-by: Fengnan Chang \n---\n fs/buffer.c | 2 ++\n fs/ext4/super.c | 12 +++++++++++-\n include/linux/buffer_head.h | 2 ++\n 3 files changed, 15 insertions(+), 1 deletion(-)","diff":"diff --git a/fs/buffer.c b/fs/buffer.c\nindex 2d2e3ecec6b2b..b41d54b8b1f4d 100644\n--- a/fs/buffer.c\n+++ b/fs/buffer.c\n@@ -145,6 +145,7 @@ static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)\n {\n \tif (uptodate) {\n \t\tset_buffer_uptodate(bh);\n+\t\tclear_buffer_read_io_error(bh);\n \t} else {\n \t\t/* This happens, due to failed read-ahead attempts. */\n \t\tclear_buffer_uptodate(bh);\n@@ -167,6 +168,7 @@ void end_buffer_write_sync(struct buffer_head *bh, int uptodate)\n {\n \tif (uptodate) {\n \t\tset_buffer_uptodate(bh);\n+\t\tclear_buffer_read_io_error(bh);\n \t} else {\n \t\tbuffer_io_error(bh, \", lost sync page write\");\n \t\tmark_buffer_write_io_error(bh);\ndiff --git a/fs/ext4/super.c b/fs/ext4/super.c\nindex 781c083000c2e..89a99851864a0 100644\n--- a/fs/ext4/super.c\n+++ b/fs/ext4/super.c\n@@ -198,7 +198,13 @@ int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,\n {\n \tBUG_ON(!buffer_locked(bh));\n \n+\tif (!buffer_write_io_error(bh) && buffer_read_io_error(bh)) {\n+\t\tunlock_buffer(bh);\n+\t\treturn -EIO;\n+\t}\n+\n \tif (ext4_buffer_uptodate(bh)) {\n+\t\tclear_buffer_read_io_error(bh);\n \t\tunlock_buffer(bh);\n \t\treturn 0;\n \t}\n@@ -206,8 +212,12 @@ int ext4_read_bh(struct buffer_head *bh, blk_opf_t op_flags,\n \t__ext4_read_bh(bh, op_flags, end_io, simu_fail);\n \n \twait_on_buffer(bh);\n-\tif (buffer_uptodate(bh))\n+\tif (buffer_uptodate(bh)) {\n+\t\tclear_buffer_read_io_error(bh);\n \t\treturn 0;\n+\t}\n+\tif (!buffer_write_io_error(bh))\n+\t\tset_buffer_read_io_error(bh);\n \treturn -EIO;\n }\n \ndiff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h\nindex b16b88bfbc3e7..be8bedcde379e 100644\n--- a/include/linux/buffer_head.h\n+++ b/include/linux/buffer_head.h\n@@ -29,6 +29,7 @@ enum bh_state_bits {\n \tBH_Delay,\t/* Buffer is not yet allocated on disk */\n \tBH_Boundary,\t/* Block is followed by a discontiguity */\n \tBH_Write_EIO,\t/* I/O error on write */\n+\tBH_Read_EIO,\t/* I/O error on read */\n \tBH_Unwritten,\t/* Buffer is allocated on disk but not written */\n \tBH_Quiet,\t/* Buffer Error Prinks to be quiet */\n \tBH_Meta,\t/* Buffer contains metadata */\n@@ -132,6 +133,7 @@ BUFFER_FNS(Async_Write, async_write)\n BUFFER_FNS(Delay, delay)\n BUFFER_FNS(Boundary, boundary)\n BUFFER_FNS(Write_EIO, write_io_error)\n+BUFFER_FNS(Read_EIO, read_io_error)\n BUFFER_FNS(Unwritten, unwritten)\n BUFFER_FNS(Meta, meta)\n BUFFER_FNS(Prio, prio)\n","prefixes":["RFC","1/1"]}