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[PATCH] netfs: If didn't read new data then abandon retry

Lizhi Xu posted 1 patch 2 weeks, 1 day ago 
fs/9p/vfs_addr.c         | 5 ++++-
fs/netfs/buffered_read.c | 1 +
fs/netfs/direct_read.c   | 1 +
fs/netfs/read_collect.c  | 9 ++++++---
fs/netfs/read_retry.c    | 2 ++
include/linux/netfs.h    | 2 ++
6 files changed, 16 insertions(+), 4 deletions(-)
[PATCH] netfs: If didn't read new data then abandon retry
Posted by Lizhi Xu 2 weeks, 1 day ago 
syzkaller reported a three-level circle calls (netfs_rreq_assess,
netfs_retry_reads, netfs_rreq_terminated), during an unbuffered or direct
I/O read.  [1]

netfs_rreq_terminated() only checks that subreq's transferred is greater
than consumed and then sets the retry flag. There is no limit on the number
of retries, and there is no judgment on whether the retry is effective in
reading new data. This hitting the stack guard page.

To avoid the issue, let's add retry read times and the length of the data
just read in struct netfs_io_subrequest, use them to assess the state of a
read request and decide what to do retry.

[1]
BUG: TASK stack guard page was hit at ffffc9000482ff48 (stack is ffffc90004830000..ffffc90004838000)
Oops: stack guard page: 0000 [#1] PREEMPT SMP KASAN NOPTI
CPU: 3 UID: 0 PID: 6237 Comm: syz-executor663 Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:mark_lock+0x25/0xc60 kernel/locking/lockdep.c:4686
Code: 90 90 90 90 90 55 48 89 e5 41 57 41 56 41 89 d6 48 ba 00 00 00 00 00 fc ff df 41 55 41 54 53 48 83 e4 f0 48 81 ec 10 01 00 00 <48> c7 44 24 30 b3 8a b5 41 48 8d 44 24 30 48 c7 44 24 38 c0 4d 7a
RSP: 0018:ffffc9000482ff50 EFLAGS: 00010086
RAX: 000000000000000c RBX: ffff8880306c2fba RCX: 0000000000000002
RDX: dffffc0000000000 RSI: ffff8880306c2f98 RDI: ffff8880306c2440
RBP: ffffc90004830088 R08: 0000000000000000 R09: 0000000000000006
R10: ffffffff96e2dd27 R11: 0000000000000000 R12: dffffc0000000000
R13: ffff8880306c2f98 R14: 0000000000000008 R15: ffff8880306c2440
FS:  00007fedf3b6e6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffc9000482ff48 CR3: 000000002c910000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <#DF>
 </#DF>
 <TASK>
 mark_usage kernel/locking/lockdep.c:4646 [inline]
 __lock_acquire+0x906/0x3ce0 kernel/locking/lockdep.c:5156
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
 ___slab_alloc+0x123/0x1880 mm/slub.c:3695
 __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3908
 __slab_alloc_node mm/slub.c:3961 [inline]
 slab_alloc_node mm/slub.c:4122 [inline]
 kmem_cache_alloc_noprof+0x2a7/0x2f0 mm/slub.c:4141
 radix_tree_node_alloc.constprop.0+0x1e8/0x350 lib/radix-tree.c:253
 idr_get_free+0x528/0xa40 lib/radix-tree.c:1506
 idr_alloc_u32+0x191/0x2f0 lib/idr.c:46
 idr_alloc+0xc1/0x130 lib/idr.c:87
 p9_tag_alloc+0x394/0x870 net/9p/client.c:321
 p9_client_prepare_req+0x19f/0x4d0 net/9p/client.c:644
 p9_client_zc_rpc.constprop.0+0x105/0x880 net/9p/client.c:793
 p9_client_read_once+0x443/0x820 net/9p/client.c:1570
 p9_client_read+0x13f/0x1b0 net/9p/client.c:1534
 v9fs_issue_read+0x115/0x310 fs/9p/vfs_addr.c:74
 netfs_retry_read_subrequests fs/netfs/read_retry.c:60 [inline]
 netfs_retry_reads+0x153a/0x1d00 fs/netfs/read_retry.c:232
 netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
 netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
 netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
 netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
 netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
 netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
 netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
 ...
 netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
 netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
 netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
 netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
 netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
 netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
 netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
 netfs_dispatch_unbuffered_reads fs/netfs/direct_read.c:103 [inline]
 netfs_unbuffered_read fs/netfs/direct_read.c:127 [inline]
 netfs_unbuffered_read_iter_locked+0x12f6/0x19b0 fs/netfs/direct_read.c:221
 netfs_unbuffered_read_iter+0xc5/0x100 fs/netfs/direct_read.c:256
 v9fs_file_read_iter+0xbf/0x100 fs/9p/vfs_file.c:361
 do_iter_readv_writev+0x614/0x7f0 fs/read_write.c:832
 vfs_readv+0x4cf/0x890 fs/read_write.c:1025
 do_preadv fs/read_write.c:1142 [inline]
 __do_sys_preadv fs/read_write.c:1192 [inline]
 __se_sys_preadv fs/read_write.c:1187 [inline]
 __x64_sys_preadv+0x22d/0x310 fs/read_write.c:1187
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fedf3bd4dd9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fedf3b6e168 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
RAX: ffffffffffffffda RBX: 00007fedf3c5e318 RCX: 00007fedf3bd4dd9
RDX: 0000000000000001 RSI: 00000000200015c0 RDI: 0000000000000003
RBP: 00007fedf3c5e310 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fedf3c5e31c
R13: 000000000000000b R14: 00007fffe9d355b0 R15: 00007fffe9d35698
 </TASK>

Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
Reported-and-tested-by: syzbot+1fc6f64c40a9d143cfb6@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=1fc6f64c40a9d143cfb6
Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
---
 fs/9p/vfs_addr.c         | 5 ++++-
 fs/netfs/buffered_read.c | 1 +
 fs/netfs/direct_read.c   | 1 +
 fs/netfs/read_collect.c  | 9 ++++++---
 fs/netfs/read_retry.c    | 2 ++
 include/linux/netfs.h    | 2 ++
 6 files changed, 16 insertions(+), 4 deletions(-)

diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
index 819c75233235..9fcc77bc77bd 100644
--- a/fs/9p/vfs_addr.c
+++ b/fs/9p/vfs_addr.c
@@ -80,8 +80,11 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
 	if (pos + total >= i_size_read(rreq->inode))
 		__set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags);
 
-	if (!err)
+	if (!err) {
 		subreq->transferred += total;
+		subreq->fresh_len = total;
+	} else
+		subreq->fresh_len = 0;
 
 	netfs_read_subreq_terminated(subreq, err, false);
 }
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index c40e226053cc..a233412ba08f 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -233,6 +233,7 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
 
 		subreq->start	= start;
 		subreq->len	= size;
+		subreq->rretry_times = 0;
 
 		atomic_inc(&rreq->nr_outstanding);
 		spin_lock_bh(&rreq->lock);
diff --git a/fs/netfs/direct_read.c b/fs/netfs/direct_read.c
index b1a66a6e6bc2..beb81e06d13b 100644
--- a/fs/netfs/direct_read.c
+++ b/fs/netfs/direct_read.c
@@ -66,6 +66,7 @@ static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq)
 		subreq->source	= NETFS_DOWNLOAD_FROM_SERVER;
 		subreq->start	= start;
 		subreq->len	= size;
+		subreq->rretry_times = 0;
 
 		atomic_inc(&rreq->nr_outstanding);
 		spin_lock_bh(&rreq->lock);
diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index b18c65ba5580..805e8f400797 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -509,9 +509,12 @@ void netfs_read_subreq_terminated(struct netfs_io_subrequest *subreq,
 		} else {
 			trace_netfs_sreq(subreq, netfs_sreq_trace_short);
 			if (subreq->transferred > subreq->consumed) {
-				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
-				__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
-				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
+				/* if we didn't read new data, abandon retry*/
+				if (subreq->rretry_times && subreq->fresh_len) {
+					__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
+					__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
+					set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
+				}
 			} else if (!__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
 				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
 				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
index 0350592ea804..7aa0420cb4c4 100644
--- a/fs/netfs/read_retry.c
+++ b/fs/netfs/read_retry.c
@@ -56,6 +56,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 			if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
 				break;
 			if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
+				subreq->rretry_times++;
 				netfs_reset_iter(subreq);
 				netfs_reissue_read(rreq, subreq);
 			}
@@ -183,6 +184,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
 					goto abandon;
 				subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
 				subreq->start = start;
+				subreq->rretry_times = 0;
 
 				/* We get two refs, but need just one. */
 				netfs_put_subrequest(subreq, false, netfs_sreq_trace_new);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 5eaceef41e6c..c0b1f058f09a 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -191,6 +191,8 @@ struct netfs_io_subrequest {
 	unsigned char		curr_folio_order; /* Order of folio */
 	struct folio_queue	*curr_folioq;	/* Queue segment in which current folio resides */
 	unsigned long		flags;
+	size_t			fresh_len;	/* The length of the data just read */
+	u8			rretry_times;   /* The times of retry read */
 #define NETFS_SREQ_COPY_TO_CACHE	0	/* Set if should copy the data to the cache */
 #define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
 #define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */
-- 
2.43.0
Re: [PATCH] netfs: If didn't read new data then abandon retry
Posted by asmadeus@codewreck.org 1 week ago 
David,

I see now you weren't in Cc, does that patch make sense to you?
https://lkml.kernel.org/r/20241108034020.3695718-1-lizhi.xu@windriver.com


Lizhi Xu wrote on Fri, Nov 08, 2024 at 11:40:20AM +0800:
Subject: [PATCH] netfs: If didn't read new data then abandon retry

Since this is ended up a netfs patch please run get_maintainers.pl on it
and add appropriate maintainers neext time.

(You might want to reword that subject line as well to make it more
direct ("fix infinite recursion" or something), but if English isn't
your forte maintainers probably can fix it up anyway...)


> syzkaller reported a three-level circle calls (netfs_rreq_assess,
> netfs_retry_reads, netfs_rreq_terminated), during an unbuffered or direct
> I/O read.  [1]
> 
> netfs_rreq_terminated() only checks that subreq's transferred is greater
> than consumed and then sets the retry flag. There is no limit on the number
> of retries, and there is no judgment on whether the retry is effective in
> reading new data. This hitting the stack guard page.
> 
> To avoid the issue, let's add retry read times and the length of the data
> just read in struct netfs_io_subrequest, use them to assess the state of a
> read request and decide what to do retry.
> 
> [1]
> BUG: TASK stack guard page was hit at ffffc9000482ff48 (stack is ffffc90004830000..ffffc90004838000)
> Oops: stack guard page: 0000 [#1] PREEMPT SMP KASAN NOPTI
> CPU: 3 UID: 0 PID: 6237 Comm: syz-executor663 Not tainted 6.12.0-rc6-syzkaller-00077-g2e1b3cc9d7f7 #0
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
> RIP: 0010:mark_lock+0x25/0xc60 kernel/locking/lockdep.c:4686
> Code: 90 90 90 90 90 55 48 89 e5 41 57 41 56 41 89 d6 48 ba 00 00 00 00 00 fc ff df 41 55 41 54 53 48 83 e4 f0 48 81 ec 10 01 00 00 <48> c7 44 24 30 b3 8a b5 41 48 8d 44 24 30 48 c7 44 24 38 c0 4d 7a
> RSP: 0018:ffffc9000482ff50 EFLAGS: 00010086
> RAX: 000000000000000c RBX: ffff8880306c2fba RCX: 0000000000000002
> RDX: dffffc0000000000 RSI: ffff8880306c2f98 RDI: ffff8880306c2440
> RBP: ffffc90004830088 R08: 0000000000000000 R09: 0000000000000006
> R10: ffffffff96e2dd27 R11: 0000000000000000 R12: dffffc0000000000
> R13: ffff8880306c2f98 R14: 0000000000000008 R15: ffff8880306c2440
> FS:  00007fedf3b6e6c0(0000) GS:ffff88806a900000(0000) knlGS:0000000000000000
> CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: ffffc9000482ff48 CR3: 000000002c910000 CR4: 0000000000352ef0
> DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
> DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
> Call Trace:
>  <#DF>
>  </#DF>
>  <TASK>
>  mark_usage kernel/locking/lockdep.c:4646 [inline]
>  __lock_acquire+0x906/0x3ce0 kernel/locking/lockdep.c:5156
>  lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
>  local_lock_acquire include/linux/local_lock_internal.h:29 [inline]
>  ___slab_alloc+0x123/0x1880 mm/slub.c:3695
>  __slab_alloc.constprop.0+0x56/0xb0 mm/slub.c:3908
>  __slab_alloc_node mm/slub.c:3961 [inline]
>  slab_alloc_node mm/slub.c:4122 [inline]
>  kmem_cache_alloc_noprof+0x2a7/0x2f0 mm/slub.c:4141
>  radix_tree_node_alloc.constprop.0+0x1e8/0x350 lib/radix-tree.c:253
>  idr_get_free+0x528/0xa40 lib/radix-tree.c:1506
>  idr_alloc_u32+0x191/0x2f0 lib/idr.c:46
>  idr_alloc+0xc1/0x130 lib/idr.c:87
>  p9_tag_alloc+0x394/0x870 net/9p/client.c:321
>  p9_client_prepare_req+0x19f/0x4d0 net/9p/client.c:644
>  p9_client_zc_rpc.constprop.0+0x105/0x880 net/9p/client.c:793
>  p9_client_read_once+0x443/0x820 net/9p/client.c:1570
>  p9_client_read+0x13f/0x1b0 net/9p/client.c:1534
>  v9fs_issue_read+0x115/0x310 fs/9p/vfs_addr.c:74
>  netfs_retry_read_subrequests fs/netfs/read_retry.c:60 [inline]
>  netfs_retry_reads+0x153a/0x1d00 fs/netfs/read_retry.c:232
>  netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
>  netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
>  netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
>  netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
>  netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
>  netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
>  netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
>  ...
>  netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
>  netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
>  netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
>  netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
>  netfs_retry_reads+0x155e/0x1d00 fs/netfs/read_retry.c:235
>  netfs_rreq_assess+0x5d3/0x870 fs/netfs/read_collect.c:371
>  netfs_rreq_terminated+0xe5/0x110 fs/netfs/read_collect.c:407
>  netfs_dispatch_unbuffered_reads fs/netfs/direct_read.c:103 [inline]
>  netfs_unbuffered_read fs/netfs/direct_read.c:127 [inline]
>  netfs_unbuffered_read_iter_locked+0x12f6/0x19b0 fs/netfs/direct_read.c:221
>  netfs_unbuffered_read_iter+0xc5/0x100 fs/netfs/direct_read.c:256
>  v9fs_file_read_iter+0xbf/0x100 fs/9p/vfs_file.c:361
>  do_iter_readv_writev+0x614/0x7f0 fs/read_write.c:832
>  vfs_readv+0x4cf/0x890 fs/read_write.c:1025
>  do_preadv fs/read_write.c:1142 [inline]
>  __do_sys_preadv fs/read_write.c:1192 [inline]
>  __se_sys_preadv fs/read_write.c:1187 [inline]
>  __x64_sys_preadv+0x22d/0x310 fs/read_write.c:1187
>  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>  do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
>  entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7fedf3bd4dd9
> Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 51 18 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007fedf3b6e168 EFLAGS: 00000246 ORIG_RAX: 0000000000000127
> RAX: ffffffffffffffda RBX: 00007fedf3c5e318 RCX: 00007fedf3bd4dd9
> RDX: 0000000000000001 RSI: 00000000200015c0 RDI: 0000000000000003
> RBP: 00007fedf3c5e310 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000246 R12: 00007fedf3c5e31c
> R13: 000000000000000b R14: 00007fffe9d355b0 R15: 00007fffe9d35698
>  </TASK>
> 
> Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
> Reported-and-tested-by: syzbot+1fc6f64c40a9d143cfb6@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=1fc6f64c40a9d143cfb6
> Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com>
> ---
>  fs/9p/vfs_addr.c         | 5 ++++-
>  fs/netfs/buffered_read.c | 1 +
>  fs/netfs/direct_read.c   | 1 +
>  fs/netfs/read_collect.c  | 9 ++++++---
>  fs/netfs/read_retry.c    | 2 ++
>  include/linux/netfs.h    | 2 ++
>  6 files changed, 16 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/9p/vfs_addr.c b/fs/9p/vfs_addr.c
> index 819c75233235..9fcc77bc77bd 100644
> --- a/fs/9p/vfs_addr.c
> +++ b/fs/9p/vfs_addr.c
> @@ -80,8 +80,11 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
>  	if (pos + total >= i_size_read(rreq->inode))
>  		__set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags);
>  
> -	if (!err)
> +	if (!err) {
>  		subreq->transferred += total;
> +		subreq->fresh_len = total;
> +	} else
> +		subreq->fresh_len = 0;
>  
>  	netfs_read_subreq_terminated(subreq, err, false);
>  }
> diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
> index c40e226053cc..a233412ba08f 100644
> --- a/fs/netfs/buffered_read.c
> +++ b/fs/netfs/buffered_read.c
> @@ -233,6 +233,7 @@ static void netfs_read_to_pagecache(struct netfs_io_request *rreq)
>  
>  		subreq->start	= start;
>  		subreq->len	= size;
> +		subreq->rretry_times = 0;
>  
>  		atomic_inc(&rreq->nr_outstanding);
>  		spin_lock_bh(&rreq->lock);
> diff --git a/fs/netfs/direct_read.c b/fs/netfs/direct_read.c
> index b1a66a6e6bc2..beb81e06d13b 100644
> --- a/fs/netfs/direct_read.c
> +++ b/fs/netfs/direct_read.c
> @@ -66,6 +66,7 @@ static int netfs_dispatch_unbuffered_reads(struct netfs_io_request *rreq)
>  		subreq->source	= NETFS_DOWNLOAD_FROM_SERVER;
>  		subreq->start	= start;
>  		subreq->len	= size;
> +		subreq->rretry_times = 0;
>  
>  		atomic_inc(&rreq->nr_outstanding);
>  		spin_lock_bh(&rreq->lock);
> diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
> index b18c65ba5580..805e8f400797 100644
> --- a/fs/netfs/read_collect.c
> +++ b/fs/netfs/read_collect.c
> @@ -509,9 +509,12 @@ void netfs_read_subreq_terminated(struct netfs_io_subrequest *subreq,
>  		} else {
>  			trace_netfs_sreq(subreq, netfs_sreq_trace_short);
>  			if (subreq->transferred > subreq->consumed) {
> -				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
> -				__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
> -				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
> +				/* if we didn't read new data, abandon retry*/
> +				if (subreq->rretry_times && subreq->fresh_len) {
> +					__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
> +					__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
> +					set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
> +				}
>  			} else if (!__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
>  				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
>  				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
> diff --git a/fs/netfs/read_retry.c b/fs/netfs/read_retry.c
> index 0350592ea804..7aa0420cb4c4 100644
> --- a/fs/netfs/read_retry.c
> +++ b/fs/netfs/read_retry.c
> @@ -56,6 +56,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
>  			if (test_bit(NETFS_SREQ_FAILED, &subreq->flags))
>  				break;
>  			if (__test_and_clear_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags)) {
> +				subreq->rretry_times++;
>  				netfs_reset_iter(subreq);
>  				netfs_reissue_read(rreq, subreq);
>  			}
> @@ -183,6 +184,7 @@ static void netfs_retry_read_subrequests(struct netfs_io_request *rreq)
>  					goto abandon;
>  				subreq->source = NETFS_DOWNLOAD_FROM_SERVER;
>  				subreq->start = start;
> +				subreq->rretry_times = 0;
>  
>  				/* We get two refs, but need just one. */
>  				netfs_put_subrequest(subreq, false, netfs_sreq_trace_new);
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index 5eaceef41e6c..c0b1f058f09a 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -191,6 +191,8 @@ struct netfs_io_subrequest {
>  	unsigned char		curr_folio_order; /* Order of folio */
>  	struct folio_queue	*curr_folioq;	/* Queue segment in which current folio resides */
>  	unsigned long		flags;
> +	size_t			fresh_len;	/* The length of the data just read */
> +	u8			rretry_times;   /* The times of retry read */
>  #define NETFS_SREQ_COPY_TO_CACHE	0	/* Set if should copy the data to the cache */
>  #define NETFS_SREQ_CLEAR_TAIL		1	/* Set if the rest of the read should be cleared */
>  #define NETFS_SREQ_SEEK_DATA_READ	3	/* Set if ->read() should SEEK_DATA first */

-- 
Dominique Martinet | Asmadeus

Patchew 2.1-devel-b67e4c2

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