netfs: zero the tail of a short DIO/unbuffered readgrafted

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 <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 59 insertions, 0 deletions

diff --git a/include/scsi/scsi_eh.h b/include/scsi/scsi_eh.h
new file mode 100644
index 000000000..15679be90
--- /dev/null
+++ b/include/scsi/scsi_eh.h
@@ -0,0 +1,59 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _SCSI_SCSI_EH_H
+#define _SCSI_SCSI_EH_H
+
+#include <linux/scatterlist.h>
+
+#include <scsi/scsi_cmnd.h>
+#include <scsi/scsi_common.h>
+struct scsi_device;
+struct Scsi_Host;
+
+extern void scsi_eh_finish_cmd(struct scsi_cmnd *scmd,
+			       struct list_head *done_q);
+extern void scsi_eh_flush_done_q(struct list_head *done_q);
+extern void scsi_report_bus_reset(struct Scsi_Host *, int);
+extern void scsi_report_device_reset(struct Scsi_Host *, int, int);
+extern int scsi_block_when_processing_errors(struct scsi_device *);
+extern bool scsi_command_normalize_sense(const struct scsi_cmnd *cmd,
+					 struct scsi_sense_hdr *sshdr);
+extern enum scsi_disposition scsi_check_sense(struct scsi_cmnd *);
+
+static inline bool scsi_sense_is_deferred(const struct scsi_sense_hdr *sshdr)
+{
+	return ((sshdr->response_code >= 0x70) && (sshdr->response_code & 1));
+}
+
+extern bool scsi_get_sense_info_fld(const u8 *sense_buffer, int sb_len,
+				    u64 *info_out);
+
+extern int scsi_ioctl_reset(struct scsi_device *, int __user *);
+
+struct scsi_eh_save {
+	/* saved state */
+	int result;
+	unsigned int resid_len;
+	int eh_eflags;
+	enum dma_data_direction data_direction;
+	unsigned underflow;
+	unsigned char cmd_len;
+	unsigned char prot_op;
+	unsigned char cmnd[32];
+	struct scsi_data_buffer sdb;
+	struct scatterlist sense_sgl;
+
+	/* struct request fields */
+#ifdef CONFIG_BLK_INLINE_ENCRYPTION
+	struct bio_crypt_ctx *rq_crypt_ctx;
+	struct blk_crypto_keyslot *rq_crypt_keyslot;
+#endif
+};
+
+extern void scsi_eh_prep_cmnd(struct scsi_cmnd *scmd,
+		struct scsi_eh_save *ses, unsigned char *cmnd,
+		int cmnd_size, unsigned sense_bytes);
+
+extern void scsi_eh_restore_cmnd(struct scsi_cmnd* scmd,
+		struct scsi_eh_save *ses);
+
+#endif /* _SCSI_SCSI_EH_H */