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/md/dm-pcache/segment.h | 74 ++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 74 insertions(+) create mode 100644 drivers/md/dm-pcache/segment.h (limited to 'drivers/md/dm-pcache/segment.h') diff --git a/drivers/md/dm-pcache/segment.h b/drivers/md/dm-pcache/segment.h new file mode 100644 index 000000000..deca1ddcb --- /dev/null +++ b/drivers/md/dm-pcache/segment.h @@ -0,0 +1,74 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +#ifndef _PCACHE_SEGMENT_H +#define _PCACHE_SEGMENT_H + +#include +#include + +#include "pcache_internal.h" + +struct pcache_segment_info { + struct pcache_meta_header header; + __u32 flags; + __u32 next_seg; +}; + +#define PCACHE_SEG_INFO_FLAGS_HAS_NEXT BIT(0) + +#define PCACHE_SEG_INFO_FLAGS_TYPE_MASK GENMASK(4, 1) +#define PCACHE_SEGMENT_TYPE_CACHE_DATA 1 + +static inline bool segment_info_has_next(struct pcache_segment_info *seg_info) +{ + return (seg_info->flags & PCACHE_SEG_INFO_FLAGS_HAS_NEXT); +} + +static inline void segment_info_set_type(struct pcache_segment_info *seg_info, u8 type) +{ + seg_info->flags &= ~PCACHE_SEG_INFO_FLAGS_TYPE_MASK; + seg_info->flags |= FIELD_PREP(PCACHE_SEG_INFO_FLAGS_TYPE_MASK, type); +} + +static inline u8 segment_info_get_type(struct pcache_segment_info *seg_info) +{ + return FIELD_GET(PCACHE_SEG_INFO_FLAGS_TYPE_MASK, seg_info->flags); +} + +struct pcache_segment_pos { + struct pcache_segment *segment; /* Segment associated with the position */ + u32 off; /* Offset within the segment */ +}; + +struct pcache_segment_init_options { + u8 type; + u32 seg_id; + u32 data_off; + + struct pcache_segment_info *seg_info; +}; + +struct pcache_segment { + struct pcache_cache_dev *cache_dev; + + void *data; + u32 data_size; + u32 seg_id; + + struct pcache_segment_info *seg_info; +}; + +int segment_copy_to_bio(struct pcache_segment *segment, + u32 data_off, u32 data_len, struct bio *bio, u32 bio_off); +int segment_copy_from_bio(struct pcache_segment *segment, + u32 data_off, u32 data_len, struct bio *bio, u32 bio_off); + +static inline void segment_pos_advance(struct pcache_segment_pos *seg_pos, u32 len) +{ + BUG_ON(seg_pos->off + len > seg_pos->segment->data_size); + + seg_pos->off += len; +} + +void pcache_segment_init(struct pcache_cache_dev *cache_dev, struct pcache_segment *segment, + struct pcache_segment_init_options *options); +#endif /* _PCACHE_SEGMENT_H */ -- cgit v1.3.1