From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org --- drivers/base/regmap/regcache-flat.c | 175 ++++++++++++++++++++++++++++++++++++ 1 file changed, 175 insertions(+) create mode 100644 drivers/base/regmap/regcache-flat.c (limited to 'drivers/base/regmap/regcache-flat.c') diff --git a/drivers/base/regmap/regcache-flat.c b/drivers/base/regmap/regcache-flat.c new file mode 100644 index 000000000..be8497fd2 --- /dev/null +++ b/drivers/base/regmap/regcache-flat.c @@ -0,0 +1,175 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Register cache access API - flat caching support +// +// Copyright 2012 Wolfson Microelectronics plc +// +// Author: Mark Brown + +#include +#include +#include +#include +#include +#include +#include + +#include "internal.h" + +static inline unsigned int regcache_flat_get_index(const struct regmap *map, + unsigned int reg) +{ + return regcache_get_index_by_order(map, reg); +} + +struct regcache_flat_data { + unsigned long *valid; + unsigned int data[]; +}; + +static int regcache_flat_init(struct regmap *map) +{ + unsigned int cache_size; + struct regcache_flat_data *cache; + + if (!map || map->reg_stride_order < 0 || !map->max_register_is_set) + return -EINVAL; + + cache_size = regcache_flat_get_index(map, map->max_register) + 1; + cache = kzalloc_flex(*cache, data, cache_size, map->alloc_flags); + if (!cache) + return -ENOMEM; + + cache->valid = bitmap_zalloc(cache_size, map->alloc_flags); + if (!cache->valid) + goto err_free; + + map->cache = cache; + + return 0; + +err_free: + kfree(cache); + return -ENOMEM; +} + +static void regcache_flat_exit(struct regmap *map) +{ + struct regcache_flat_data *cache = map->cache; + + if (cache) + bitmap_free(cache->valid); + + kfree(cache); + map->cache = NULL; +} + +static int regcache_flat_populate(struct regmap *map) +{ + struct regcache_flat_data *cache = map->cache; + unsigned int i; + + for (i = 0; i < map->num_reg_defaults; i++) { + unsigned int reg = map->reg_defaults[i].reg; + unsigned int index = regcache_flat_get_index(map, reg); + + cache->data[index] = map->reg_defaults[i].def; + __set_bit(index, cache->valid); + } + + if (map->reg_default_cb) { + dev_dbg(map->dev, + "Populating regcache_flat using reg_default_cb callback\n"); + + for (i = 0; i <= map->max_register; i += map->reg_stride) { + unsigned int index = regcache_flat_get_index(map, i); + unsigned int value; + + if (test_bit(index, cache->valid)) + continue; + + if (map->reg_default_cb(map->dev, i, &value)) + continue; + + cache->data[index] = value; + __set_bit(index, cache->valid); + } + } + + return 0; +} + +static int regcache_flat_read(struct regmap *map, + unsigned int reg, unsigned int *value) +{ + struct regcache_flat_data *cache = map->cache; + unsigned int index = regcache_flat_get_index(map, reg); + + /* legacy behavior: ignore validity, but warn the user */ + if (unlikely(!test_bit(index, cache->valid))) + dev_warn_once(map->dev, + "using zero-initialized flat cache, this may cause unexpected behavior"); + + *value = cache->data[index]; + + return 0; +} + +static int regcache_flat_sparse_read(struct regmap *map, + unsigned int reg, unsigned int *value) +{ + struct regcache_flat_data *cache = map->cache; + unsigned int index = regcache_flat_get_index(map, reg); + + if (unlikely(!test_bit(index, cache->valid))) + return -ENOENT; + + *value = cache->data[index]; + + return 0; +} + +static int regcache_flat_write(struct regmap *map, unsigned int reg, + unsigned int value) +{ + struct regcache_flat_data *cache = map->cache; + unsigned int index = regcache_flat_get_index(map, reg); + + cache->data[index] = value; + __set_bit(index, cache->valid); + + return 0; +} + +static int regcache_flat_drop(struct regmap *map, unsigned int min, + unsigned int max) +{ + struct regcache_flat_data *cache = map->cache; + unsigned int bitmap_min = regcache_flat_get_index(map, min); + unsigned int bitmap_max = regcache_flat_get_index(map, max); + + bitmap_clear(cache->valid, bitmap_min, bitmap_max + 1 - bitmap_min); + + return 0; +} + +struct regcache_ops regcache_flat_ops = { + .type = REGCACHE_FLAT, + .name = "flat", + .init = regcache_flat_init, + .exit = regcache_flat_exit, + .populate = regcache_flat_populate, + .read = regcache_flat_read, + .write = regcache_flat_write, +}; + +struct regcache_ops regcache_flat_sparse_ops = { + .type = REGCACHE_FLAT_S, + .name = "flat-sparse", + .init = regcache_flat_init, + .exit = regcache_flat_exit, + .populate = regcache_flat_populate, + .read = regcache_flat_sparse_read, + .write = regcache_flat_write, + .drop = regcache_flat_drop, +}; -- cgit v1.3.1