From: Qian Yingjin <qian(a)ddn.com>
I was running traces of the read code against an RAID storage
system to understand why read requests were being misaligned
against the underlying RAID strips. I found that the page end
offset calculation in filemap_get_read_batch() was off by one.
When a read is submitted with end offset 1048575, then it
calculates the end page for read of 256 when it should be 255.
"last_index" is the index of the page beyond the end of the read
and it should be skipped when get a batch of pages for read in
@filemap_get_read_batch().
The below simple patch fixes the problem. This code was introduced
in kernel 5.12.
Fixes: cbd59c48ae2b ("mm/filemap: use head pages in generic_file_buffered_read")
Signed-off-by: Qian Yingjin <qian(a)ddn.com>
---
mm/filemap.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index c4d4ace9cc70..b7754760c09a 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2371,7 +2371,7 @@ static void shrink_readahead_size_eio(struct file_ra_state *ra)
* clear so that the caller can take the appropriate action.
*/
static void filemap_get_read_batch(struct address_space *mapping,
- pgoff_t index, pgoff_t max, struct folio_batch *fbatch)
+ pgoff_t index, pgoff_t last_index, struct folio_batch *fbatch)
{
XA_STATE(xas, &mapping->i_pages, index);
struct folio *folio;
@@ -2380,7 +2380,11 @@ static void filemap_get_read_batch(struct address_space *mapping,
for (folio = xas_load(&xas); folio; folio = xas_next(&xas)) {
if (xas_retry(&xas, folio))
continue;
- if (xas.xa_index > max || xa_is_value(folio))
+ /*
+ * "last_index" is the index of the page beyond the end of
+ * the read.
+ */
+ if (xas.xa_index >= last_index || xa_is_value(folio))
break;
if (xa_is_sibling(folio))
break;
@@ -2588,6 +2592,7 @@ static int filemap_get_pages(struct kiocb *iocb, struct iov_iter *iter,
struct folio *folio;
int err = 0;
+ /* "last_index" is the index of the page beyond the end of the read */
last_index = DIV_ROUND_UP(iocb->ki_pos + iter->count, PAGE_SIZE);
retry:
if (fatal_signal_pending(current))
--
2.34.1
The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable(a)vger.kernel.org>.
Possible dependencies:
b389286d0234 ("drm/mgag200: Fix PLL setup for G200_SE_A rev >=4")
877507bb954e ("drm/mgag200: Provide per-device callbacks for PIXPLLC")
8aeeb3144fe2 ("drm/mgag200: Provide per-device callbacks for BMC synchronization")
f639f74a7895 ("drm/mgag200: Add per-device callbacks")
1baf9127c482 ("drm/mgag200: Replace simple-KMS with regular atomic helpers")
4f4dc37e374c ("drm/mgag200: Reorganize before dropping simple-KMS helpers")
ed2ef21f1089 ("drm/mgag200: Store primary plane's color format in CRTC state")
2d70b9a1482e ("drm/mgag200: Acquire I/O-register lock in atomic_commit_tail function")
1ee181fe958a ("drm/mgag200: Move DAC-register setup into model-specific code")
44373151ab42 ("drm/mgag200: Split mgag200_modeset_init()")
98da4b99a052 ("drm/mgag200: Store maximum resolution and memory bandwidth in device info")
21e74bf99596 ("drm/mgag200: Store HW_BUG_NO_STARTADD flag in device info")
b9a577a407d9 ("drm/mgag200: Add struct mgag200_device_info")
b62d943e9686 ("drm/mgag200: Implement new init logic")
d45e32c9d98c ("drm/mgag200: Call mgag200_device_probe_vram() from per-model init")
ce19021fd99a ("drm/mgag200: Move PCI-option setup into model-specific code")
85397f6bc4ff ("drm/mgag200: Initialize each model in separate function")
73f54d5d9682 ("drm/mgag200: Remove special case for G200SE with <2 MiB")
475e2b970cc3 ("drm/mgag200: Split up connector's mode_valid helper")
69340e529a06 ("drm/mgag200: Test memory requirements in drm_mode_config_funcs.mode_valid")
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From b389286d0234e1edbaf62ed8bc0892a568c33662 Mon Sep 17 00:00:00 2001
From: Jocelyn Falempe <jfalempe(a)redhat.com>
Date: Thu, 13 Oct 2022 15:28:10 +0200
Subject: [PATCH] drm/mgag200: Fix PLL setup for G200_SE_A rev >=4
For G200_SE_A, PLL M setting is wrong, which leads to blank screen,
or "signal out of range" on VGA display.
previous code had "m |= 0x80" which was changed to
m |= ((pixpllcn & BIT(8)) >> 1);
Tested on G200_SE_A rev 42
This line of code was moved to another file with
commit 877507bb954e ("drm/mgag200: Provide per-device callbacks for
PIXPLLC") but can be easily backported before this commit.
v2: * put BIT(7) First to respect MSB-to-LSB (Thomas)
* Add a comment to explain that this bit must be set (Thomas)
Fixes: 2dd040946ecf ("drm/mgag200: Store values (not bits) in struct mgag200_pll_values")
Cc: stable(a)vger.kernel.org
Signed-off-by: Jocelyn Falempe <jfalempe(a)redhat.com>
Reviewed-by: Thomas Zimmermann <tzimmermann(a)suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20221013132810.521945-1-jfale…
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200se.c b/drivers/gpu/drm/mgag200/mgag200_g200se.c
index be389ed91cbd..bd6e573c9a1a 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200se.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200se.c
@@ -284,7 +284,8 @@ static void mgag200_g200se_04_pixpllc_atomic_update(struct drm_crtc *crtc,
pixpllcp = pixpllc->p - 1;
pixpllcs = pixpllc->s;
- xpixpllcm = pixpllcm | ((pixpllcn & BIT(8)) >> 1);
+ // For G200SE A, BIT(7) should be set unconditionally.
+ xpixpllcm = BIT(7) | pixpllcm;
xpixpllcn = pixpllcn;
xpixpllcp = (pixpllcs << 3) | pixpllcp;