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cifs: make sure that channel scaling is done only once

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Following a successful cifs_tree_connect, we have the code
to scale up/down the number of channels in the session.
However, it is not protected by a lock today.

As a result, this code can be executed by several processes
that select the same channel. The core functions handle this
well, as they pick chan_lock. However, we've seen cases where
smb2_reconnect throws some warnings.

To fix that, this change introduces a flags bitmap inside the
cifs_ses structure. A new flag type is used to ensure that
only one process enters this section at any time.

Signed-off-by: Shyam Prasad N <sprasad@microsoft.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
This commit is contained in:
Shyam Prasad N 2024-01-29 13:58:13 +00:00 committed by Steve French
parent 41bccc98fb
commit ee36a3b345
2 changed files with 20 additions and 3 deletions
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3
fs/smb/client/cifsglob.h
View File

@ -1032,6 +1032,8 @@ struct cifs_chan {
__u8 signkey[SMB3_SIGN_KEY_SIZE];
};
#define CIFS_SES_FLAG_SCALE_CHANNELS (0x1)
/*
* Session structure. One of these for each uid session with a particular host
*/
@ -1064,6 +1066,7 @@ struct cifs_ses {
enum securityEnum sectype; /* what security flavor was specified? */
bool sign; /* is signing required? */
bool domainAuto:1;
unsigned int flags;
__u16 session_flags;
__u8 smb3signingkey[SMB3_SIGN_KEY_SIZE];
__u8 smb3encryptionkey[SMB3_ENC_DEC_KEY_SIZE];

20
fs/smb/client/smb2pdu.c
View File

@ -399,6 +399,15 @@ skip_sess_setup:
goto out;
}
spin_lock(&ses->ses_lock);
if (ses->flags & CIFS_SES_FLAG_SCALE_CHANNELS) {
spin_unlock(&ses->ses_lock);
mutex_unlock(&ses->session_mutex);
goto skip_add_channels;
}
ses->flags |= CIFS_SES_FLAG_SCALE_CHANNELS;
spin_unlock(&ses->ses_lock);
if (!rc &&
(server->capabilities & SMB2_GLOBAL_CAP_MULTI_CHANNEL)) {
mutex_unlock(&ses->session_mutex);
@ -428,17 +437,22 @@ skip_sess_setup:
if (ses->chan_max > ses->chan_count &&
ses->iface_count &&
!SERVER_IS_CHAN(server)) {
if (ses->chan_count == 1)
if (ses->chan_count == 1) {
cifs_server_dbg(VFS, "supports multichannel now\n");
queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
(SMB_INTERFACE_POLL_INTERVAL * HZ));
}
cifs_try_adding_channels(ses);
queue_delayed_work(cifsiod_wq, &tcon->query_interfaces,
(SMB_INTERFACE_POLL_INTERVAL * HZ));
}
} else {
mutex_unlock(&ses->session_mutex);
}
skip_add_channels:
spin_lock(&ses->ses_lock);
ses->flags &= ~CIFS_SES_FLAG_SCALE_CHANNELS;
spin_unlock(&ses->ses_lock);
if (smb2_command != SMB2_INTERNAL_CMD)
mod_delayed_work(cifsiod_wq, &server->reconnect, 0);