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9p: treat read return values of 0 as EOF

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If your 9p server shares a synthetic file system such as sysfs, the file
size from stat often disagrees with the actual file size.

Treat non-error reads of 0 as EOF, except in the case where the request
was for 0 bytes.

Tested:
	git@github.com:hugelgupf/p9.git, served "/" on 10.0.2.2

	bash-5.3# mount -t 9p -o trans=tcp,port=12345,cache=none 10.0.2.2 /tmp/foo
	bash-5.3# cat /tmp/foo/sys/devices/system/cpu/online
	0-47

Fixes: eb497943fa ("9p: Convert to using the netfs helper lib to do reads and caching")
Signed-off-by: Barret Rhoden <brho@google.com>
Message-ID: <20260702090941.1298188-1-brho@google.com>
Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
This commit is contained in:
Barret Rhoden 2026-07-02 09:09:32 +00:00 committed by Dominique Martinet
parent 9b4cf60c6b
commit a3a6212c7d
1 changed files with 3 additions and 0 deletions
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3
fs/9p/vfs_addr.c
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@ -99,6 +99,7 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
char *target;
unsigned long long pos = subreq->start + subreq->transferred;
int total = 0, err, len, n;
size_t to_read = iov_iter_count(&subreq->io_iter);
if (S_ISLNK(rreq->inode->i_mode)) {
/* p9_client_readlink() must not be called for legacy protocols
@ -131,6 +132,8 @@ static void v9fs_issue_read(struct netfs_io_subrequest *subreq)
__set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
if (pos + total >= i_size_read(rreq->inode))
__set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags);
if (!err && !total && to_read)
__set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags);
if (!err && total) {
subreq->transferred += total;
__set_bit(NETFS_SREQ_MADE_PROGRESS, &subreq->flags);