Merge tag 'for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mst/vhost

[cris-mirror.git] / fs / cifs / misc.c

/*
 *   fs/cifs/misc.c
 *
 *   Copyright (C) International Business Machines  Corp., 2002,2008
 *   Author(s): Steve French (sfrench@us.ibm.com)
 *
 *   This library is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Lesser General Public License as published
 *   by the Free Software Foundation; either version 2.1 of the License, or
 *   (at your option) any later version.
 *
 *   This library is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
 *   the GNU Lesser General Public License for more details.
 *
 *   You should have received a copy of the GNU Lesser General Public License
 *   along with this library; if not, write to the Free Software
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */

#include <linux/slab.h>
#include <linux/ctype.h>
#include <linux/mempool.h>
#include <linux/vmalloc.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_debug.h"
#include "smberr.h"
#include "nterr.h"
#include "cifs_unicode.h"
#include "smb2pdu.h"

extern mempool_t *cifs_sm_req_poolp;
extern mempool_t *cifs_req_poolp;

/* The xid serves as a useful identifier for each incoming vfs request,
   in a similar way to the mid which is useful to track each sent smb,
   and CurrentXid can also provide a running counter (although it
   will eventually wrap past zero) of the total vfs operations handled
   since the cifs fs was mounted */

unsigned int
_get_xid(void)
{
        unsigned int xid;

        spin_lock(&GlobalMid_Lock);
        GlobalTotalActiveXid++;

        /* keep high water mark for number of simultaneous ops in filesystem */
        if (GlobalTotalActiveXid > GlobalMaxActiveXid)
                GlobalMaxActiveXid = GlobalTotalActiveXid;
        if (GlobalTotalActiveXid > 65000)
                cifs_dbg(FYI, "warning: more than 65000 requests active\n");
        xid = GlobalCurrentXid++;
        spin_unlock(&GlobalMid_Lock);
        return xid;
}

void
_free_xid(unsigned int xid)
{
        spin_lock(&GlobalMid_Lock);
        /* if (GlobalTotalActiveXid == 0)
                BUG(); */
        GlobalTotalActiveXid--;
        spin_unlock(&GlobalMid_Lock);
}

struct cifs_ses *
sesInfoAlloc(void)
{
        struct cifs_ses *ret_buf;

        ret_buf = kzalloc(sizeof(struct cifs_ses), GFP_KERNEL);
        if (ret_buf) {
                atomic_inc(&sesInfoAllocCount);
                ret_buf->status = CifsNew;
                ++ret_buf->ses_count;
                INIT_LIST_HEAD(&ret_buf->smb_ses_list);
                INIT_LIST_HEAD(&ret_buf->tcon_list);
                mutex_init(&ret_buf->session_mutex);
        }
        return ret_buf;
}

void
sesInfoFree(struct cifs_ses *buf_to_free)
{
        if (buf_to_free == NULL) {
                cifs_dbg(FYI, "Null buffer passed to sesInfoFree\n");
                return;
        }

        atomic_dec(&sesInfoAllocCount);
        kfree(buf_to_free->serverOS);
        kfree(buf_to_free->serverDomain);
        kfree(buf_to_free->serverNOS);
        kzfree(buf_to_free->password);
        kfree(buf_to_free->user_name);
        kfree(buf_to_free->domainName);
        kzfree(buf_to_free->auth_key.response);
        kzfree(buf_to_free);
}

struct cifs_tcon *
tconInfoAlloc(void)
{
        struct cifs_tcon *ret_buf;
        ret_buf = kzalloc(sizeof(struct cifs_tcon), GFP_KERNEL);
        if (ret_buf) {
                atomic_inc(&tconInfoAllocCount);
                ret_buf->tidStatus = CifsNew;
                ++ret_buf->tc_count;
                INIT_LIST_HEAD(&ret_buf->openFileList);
                INIT_LIST_HEAD(&ret_buf->tcon_list);
                spin_lock_init(&ret_buf->open_file_lock);
#ifdef CONFIG_CIFS_STATS
                spin_lock_init(&ret_buf->stat_lock);
#endif
        }
        return ret_buf;
}

void
tconInfoFree(struct cifs_tcon *buf_to_free)
{
        if (buf_to_free == NULL) {
                cifs_dbg(FYI, "Null buffer passed to tconInfoFree\n");
                return;
        }
        atomic_dec(&tconInfoAllocCount);
        kfree(buf_to_free->nativeFileSystem);
        kzfree(buf_to_free->password);
        kfree(buf_to_free);
}

struct smb_hdr *
cifs_buf_get(void)
{
        struct smb_hdr *ret_buf = NULL;
        /*
         * SMB2 header is bigger than CIFS one - no problems to clean some
         * more bytes for CIFS.
         */
        size_t buf_size = sizeof(struct smb2_hdr);

        /*
         * We could use negotiated size instead of max_msgsize -
         * but it may be more efficient to always alloc same size
         * albeit slightly larger than necessary and maxbuffersize
         * defaults to this and can not be bigger.
         */
        ret_buf = mempool_alloc(cifs_req_poolp, GFP_NOFS);

        /* clear the first few header bytes */
        /* for most paths, more is cleared in header_assemble */
        memset(ret_buf, 0, buf_size + 3);
        atomic_inc(&bufAllocCount);
#ifdef CONFIG_CIFS_STATS2
        atomic_inc(&totBufAllocCount);
#endif /* CONFIG_CIFS_STATS2 */

        return ret_buf;
}

void
cifs_buf_release(void *buf_to_free)
{
        if (buf_to_free == NULL) {
                /* cifs_dbg(FYI, "Null buffer passed to cifs_buf_release\n");*/
                return;
        }
        mempool_free(buf_to_free, cifs_req_poolp);

        atomic_dec(&bufAllocCount);
        return;
}

struct smb_hdr *
cifs_small_buf_get(void)
{
        struct smb_hdr *ret_buf = NULL;

/* We could use negotiated size instead of max_msgsize -
   but it may be more efficient to always alloc same size
   albeit slightly larger than necessary and maxbuffersize
   defaults to this and can not be bigger */
        ret_buf = mempool_alloc(cifs_sm_req_poolp, GFP_NOFS);
        /* No need to clear memory here, cleared in header assemble */
        /*      memset(ret_buf, 0, sizeof(struct smb_hdr) + 27);*/
        atomic_inc(&smBufAllocCount);
#ifdef CONFIG_CIFS_STATS2
        atomic_inc(&totSmBufAllocCount);
#endif /* CONFIG_CIFS_STATS2 */

        return ret_buf;
}

void
cifs_small_buf_release(void *buf_to_free)
{

        if (buf_to_free == NULL) {
                cifs_dbg(FYI, "Null buffer passed to cifs_small_buf_release\n");
                return;
        }
        mempool_free(buf_to_free, cifs_sm_req_poolp);

        atomic_dec(&smBufAllocCount);
        return;
}

void
free_rsp_buf(int resp_buftype, void *rsp)
{
        if (resp_buftype == CIFS_SMALL_BUFFER)
                cifs_small_buf_release(rsp);
        else if (resp_buftype == CIFS_LARGE_BUFFER)
                cifs_buf_release(rsp);
}

/* NB: MID can not be set if treeCon not passed in, in that
   case it is responsbility of caller to set the mid */
void
header_assemble(struct smb_hdr *buffer, char smb_command /* command */ ,
                const struct cifs_tcon *treeCon, int word_count
                /* length of fixed section (word count) in two byte units  */)
{
        char *temp = (char *) buffer;

        memset(temp, 0, 256); /* bigger than MAX_CIFS_HDR_SIZE */

        buffer->smb_buf_length = cpu_to_be32(
            (2 * word_count) + sizeof(struct smb_hdr) -
            4 /*  RFC 1001 length field does not count */  +
            2 /* for bcc field itself */) ;

        buffer->Protocol[0] = 0xFF;
        buffer->Protocol[1] = 'S';
        buffer->Protocol[2] = 'M';
        buffer->Protocol[3] = 'B';
        buffer->Command = smb_command;
        buffer->Flags = 0x00;   /* case sensitive */
        buffer->Flags2 = SMBFLG2_KNOWS_LONG_NAMES;
        buffer->Pid = cpu_to_le16((__u16)current->tgid);
        buffer->PidHigh = cpu_to_le16((__u16)(current->tgid >> 16));
        if (treeCon) {
                buffer->Tid = treeCon->tid;
                if (treeCon->ses) {
                        if (treeCon->ses->capabilities & CAP_UNICODE)
                                buffer->Flags2 |= SMBFLG2_UNICODE;
                        if (treeCon->ses->capabilities & CAP_STATUS32)
                                buffer->Flags2 |= SMBFLG2_ERR_STATUS;

                        /* Uid is not converted */
                        buffer->Uid = treeCon->ses->Suid;
                        buffer->Mid = get_next_mid(treeCon->ses->server);
                }
                if (treeCon->Flags & SMB_SHARE_IS_IN_DFS)
                        buffer->Flags2 |= SMBFLG2_DFS;
                if (treeCon->nocase)
                        buffer->Flags  |= SMBFLG_CASELESS;
                if ((treeCon->ses) && (treeCon->ses->server))
                        if (treeCon->ses->server->sign)
                                buffer->Flags2 |= SMBFLG2_SECURITY_SIGNATURE;
        }

/*  endian conversion of flags is now done just before sending */
        buffer->WordCount = (char) word_count;
        return;
}

static int
check_smb_hdr(struct smb_hdr *smb)
{
        /* does it have the right SMB "signature" ? */
        if (*(__le32 *) smb->Protocol != cpu_to_le32(0x424d53ff)) {
                cifs_dbg(VFS, "Bad protocol string signature header 0x%x\n",
                         *(unsigned int *)smb->Protocol);
                return 1;
        }

        /* if it's a response then accept */
        if (smb->Flags & SMBFLG_RESPONSE)
                return 0;

        /* only one valid case where server sends us request */
        if (smb->Command == SMB_COM_LOCKING_ANDX)
                return 0;

        cifs_dbg(VFS, "Server sent request, not response. mid=%u\n",
                 get_mid(smb));
        return 1;
}

int
checkSMB(char *buf, unsigned int total_read, struct TCP_Server_Info *server)
{
        struct smb_hdr *smb = (struct smb_hdr *)buf;
        __u32 rfclen = be32_to_cpu(smb->smb_buf_length);
        __u32 clc_len;  /* calculated length */
        cifs_dbg(FYI, "checkSMB Length: 0x%x, smb_buf_length: 0x%x\n",
                 total_read, rfclen);

        /* is this frame too small to even get to a BCC? */
        if (total_read < 2 + sizeof(struct smb_hdr)) {
                if ((total_read >= sizeof(struct smb_hdr) - 1)
                            && (smb->Status.CifsError != 0)) {
                        /* it's an error return */
                        smb->WordCount = 0;
                        /* some error cases do not return wct and bcc */
                        return 0;
                } else if ((total_read == sizeof(struct smb_hdr) + 1) &&
                                (smb->WordCount == 0)) {
                        char *tmp = (char *)smb;
                        /* Need to work around a bug in two servers here */
                        /* First, check if the part of bcc they sent was zero */
                        if (tmp[sizeof(struct smb_hdr)] == 0) {
                                /* some servers return only half of bcc
                                 * on simple responses (wct, bcc both zero)
                                 * in particular have seen this on
                                 * ulogoffX and FindClose. This leaves
                                 * one byte of bcc potentially unitialized
                                 */
                                /* zero rest of bcc */
                                tmp[sizeof(struct smb_hdr)+1] = 0;
                                return 0;
                        }
                        cifs_dbg(VFS, "rcvd invalid byte count (bcc)\n");
                } else {
                        cifs_dbg(VFS, "Length less than smb header size\n");
                }
                return -EIO;
        }

        /* otherwise, there is enough to get to the BCC */
        if (check_smb_hdr(smb))
                return -EIO;
        clc_len = smbCalcSize(smb);

        if (4 + rfclen != total_read) {
                cifs_dbg(VFS, "Length read does not match RFC1001 length %d\n",
                         rfclen);
                return -EIO;
        }

        if (4 + rfclen != clc_len) {
                __u16 mid = get_mid(smb);
                /* check if bcc wrapped around for large read responses */
                if ((rfclen > 64 * 1024) && (rfclen > clc_len)) {
                        /* check if lengths match mod 64K */
                        if (((4 + rfclen) & 0xFFFF) == (clc_len & 0xFFFF))
                                return 0; /* bcc wrapped */
                }
                cifs_dbg(FYI, "Calculated size %u vs length %u mismatch for mid=%u\n",
                         clc_len, 4 + rfclen, mid);

                if (4 + rfclen < clc_len) {
                        cifs_dbg(VFS, "RFC1001 size %u smaller than SMB for mid=%u\n",
                                 rfclen, mid);
                        return -EIO;
                } else if (rfclen > clc_len + 512) {
                        /*
                         * Some servers (Windows XP in particular) send more
                         * data than the lengths in the SMB packet would
                         * indicate on certain calls (byte range locks and
                         * trans2 find first calls in particular). While the
                         * client can handle such a frame by ignoring the
                         * trailing data, we choose limit the amount of extra
                         * data to 512 bytes.
                         */
                        cifs_dbg(VFS, "RFC1001 size %u more than 512 bytes larger than SMB for mid=%u\n",
                                 rfclen, mid);
                        return -EIO;
                }
        }
        return 0;
}

bool
is_valid_oplock_break(char *buffer, struct TCP_Server_Info *srv)
{
        struct smb_hdr *buf = (struct smb_hdr *)buffer;
        struct smb_com_lock_req *pSMB = (struct smb_com_lock_req *)buf;
        struct list_head *tmp, *tmp1, *tmp2;
        struct cifs_ses *ses;
        struct cifs_tcon *tcon;
        struct cifsInodeInfo *pCifsInode;
        struct cifsFileInfo *netfile;

        cifs_dbg(FYI, "Checking for oplock break or dnotify response\n");
        if ((pSMB->hdr.Command == SMB_COM_NT_TRANSACT) &&
           (pSMB->hdr.Flags & SMBFLG_RESPONSE)) {
                struct smb_com_transaction_change_notify_rsp *pSMBr =
                        (struct smb_com_transaction_change_notify_rsp *)buf;
                struct file_notify_information *pnotify;
                __u32 data_offset = 0;
                if (get_bcc(buf) > sizeof(struct file_notify_information)) {
                        data_offset = le32_to_cpu(pSMBr->DataOffset);

                        pnotify = (struct file_notify_information *)
                                ((char *)&pSMBr->hdr.Protocol + data_offset);
                        cifs_dbg(FYI, "dnotify on %s Action: 0x%x\n",
                                 pnotify->FileName, pnotify->Action);
                        /*   cifs_dump_mem("Rcvd notify Data: ",buf,
                                sizeof(struct smb_hdr)+60); */
                        return true;
                }
                if (pSMBr->hdr.Status.CifsError) {
                        cifs_dbg(FYI, "notify err 0x%x\n",
                                 pSMBr->hdr.Status.CifsError);
                        return true;
                }
                return false;
        }
        if (pSMB->hdr.Command != SMB_COM_LOCKING_ANDX)
                return false;
        if (pSMB->hdr.Flags & SMBFLG_RESPONSE) {
                /* no sense logging error on invalid handle on oplock
                   break - harmless race between close request and oplock
                   break response is expected from time to time writing out
                   large dirty files cached on the client */
                if ((NT_STATUS_INVALID_HANDLE) ==
                   le32_to_cpu(pSMB->hdr.Status.CifsError)) {
                        cifs_dbg(FYI, "invalid handle on oplock break\n");
                        return true;
                } else if (ERRbadfid ==
                   le16_to_cpu(pSMB->hdr.Status.DosError.Error)) {
                        return true;
                } else {
                        return false; /* on valid oplock brk we get "request" */
                }
        }
        if (pSMB->hdr.WordCount != 8)
                return false;

        cifs_dbg(FYI, "oplock type 0x%x level 0x%x\n",
                 pSMB->LockType, pSMB->OplockLevel);
        if (!(pSMB->LockType & LOCKING_ANDX_OPLOCK_RELEASE))
                return false;

        /* look up tcon based on tid & uid */
        spin_lock(&cifs_tcp_ses_lock);
        list_for_each(tmp, &srv->smb_ses_list) {
                ses = list_entry(tmp, struct cifs_ses, smb_ses_list);
                list_for_each(tmp1, &ses->tcon_list) {
                        tcon = list_entry(tmp1, struct cifs_tcon, tcon_list);
                        if (tcon->tid != buf->Tid)
                                continue;

                        cifs_stats_inc(&tcon->stats.cifs_stats.num_oplock_brks);
                        spin_lock(&tcon->open_file_lock);
                        list_for_each(tmp2, &tcon->openFileList) {
                                netfile = list_entry(tmp2, struct cifsFileInfo,
                                                     tlist);
                                if (pSMB->Fid != netfile->fid.netfid)
                                        continue;

                                cifs_dbg(FYI, "file id match, oplock break\n");
                                pCifsInode = CIFS_I(d_inode(netfile->dentry));

                                set_bit(CIFS_INODE_PENDING_OPLOCK_BREAK,
                                        &pCifsInode->flags);

                                /*
                                 * Set flag if the server downgrades the oplock
                                 * to L2 else clear.
                                 */
                                if (pSMB->OplockLevel)
                                        set_bit(
                                           CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2,
                                           &pCifsInode->flags);
                                else
                                        clear_bit(
                                           CIFS_INODE_DOWNGRADE_OPLOCK_TO_L2,
                                           &pCifsInode->flags);

                                queue_work(cifsoplockd_wq,
                                           &netfile->oplock_break);
                                netfile->oplock_break_cancelled = false;

                                spin_unlock(&tcon->open_file_lock);
                                spin_unlock(&cifs_tcp_ses_lock);
                                return true;
                        }
                        spin_unlock(&tcon->open_file_lock);
                        spin_unlock(&cifs_tcp_ses_lock);
                        cifs_dbg(FYI, "No matching file for oplock break\n");
                        return true;
                }
        }
        spin_unlock(&cifs_tcp_ses_lock);
        cifs_dbg(FYI, "Can not process oplock break for non-existent connection\n");
        return true;
}

void
dump_smb(void *buf, int smb_buf_length)
{
        if (traceSMB == 0)
                return;

        print_hex_dump(KERN_DEBUG, "", DUMP_PREFIX_NONE, 8, 2, buf,
                       smb_buf_length, true);
}

void
cifs_autodisable_serverino(struct cifs_sb_info *cifs_sb)
{
        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) {
                cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_SERVER_INUM;
                cifs_dbg(VFS, "Autodisabling the use of server inode numbers on %s. This server doesn't seem to support them properly. Hardlinks will not be recognized on this mount. Consider mounting with the \"noserverino\" option to silence this message.\n",
                         cifs_sb_master_tcon(cifs_sb)->treeName);
        }
}

void cifs_set_oplock_level(struct cifsInodeInfo *cinode, __u32 oplock)
{
        oplock &= 0xF;

        if (oplock == OPLOCK_EXCLUSIVE) {
                cinode->oplock = CIFS_CACHE_WRITE_FLG | CIFS_CACHE_READ_FLG;
                cifs_dbg(FYI, "Exclusive Oplock granted on inode %p\n",
                         &cinode->vfs_inode);
        } else if (oplock == OPLOCK_READ) {
                cinode->oplock = CIFS_CACHE_READ_FLG;
                cifs_dbg(FYI, "Level II Oplock granted on inode %p\n",
                         &cinode->vfs_inode);
        } else
                cinode->oplock = 0;
}

/*
 * We wait for oplock breaks to be processed before we attempt to perform
 * writes.
 */
int cifs_get_writer(struct cifsInodeInfo *cinode)
{
        int rc;

start:
        rc = wait_on_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK,
                         TASK_KILLABLE);
        if (rc)
                return rc;

        spin_lock(&cinode->writers_lock);
        if (!cinode->writers)
                set_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags);
        cinode->writers++;
        /* Check to see if we have started servicing an oplock break */
        if (test_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags)) {
                cinode->writers--;
                if (cinode->writers == 0) {
                        clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags);
                        wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS);
                }
                spin_unlock(&cinode->writers_lock);
                goto start;
        }
        spin_unlock(&cinode->writers_lock);
        return 0;
}

void cifs_put_writer(struct cifsInodeInfo *cinode)
{
        spin_lock(&cinode->writers_lock);
        cinode->writers--;
        if (cinode->writers == 0) {
                clear_bit(CIFS_INODE_PENDING_WRITERS, &cinode->flags);
                wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_WRITERS);
        }
        spin_unlock(&cinode->writers_lock);
}

void cifs_done_oplock_break(struct cifsInodeInfo *cinode)
{
        clear_bit(CIFS_INODE_PENDING_OPLOCK_BREAK, &cinode->flags);
        wake_up_bit(&cinode->flags, CIFS_INODE_PENDING_OPLOCK_BREAK);
}

bool
backup_cred(struct cifs_sb_info *cifs_sb)
{
        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUPUID) {
                if (uid_eq(cifs_sb->mnt_backupuid, current_fsuid()))
                        return true;
        }
        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_BACKUPGID) {
                if (in_group_p(cifs_sb->mnt_backupgid))
                        return true;
        }

        return false;
}

void
cifs_del_pending_open(struct cifs_pending_open *open)
{
        spin_lock(&tlink_tcon(open->tlink)->open_file_lock);
        list_del(&open->olist);
        spin_unlock(&tlink_tcon(open->tlink)->open_file_lock);
}

void
cifs_add_pending_open_locked(struct cifs_fid *fid, struct tcon_link *tlink,
                             struct cifs_pending_open *open)
{
        memcpy(open->lease_key, fid->lease_key, SMB2_LEASE_KEY_SIZE);
        open->oplock = CIFS_OPLOCK_NO_CHANGE;
        open->tlink = tlink;
        fid->pending_open = open;
        list_add_tail(&open->olist, &tlink_tcon(tlink)->pending_opens);
}

void
cifs_add_pending_open(struct cifs_fid *fid, struct tcon_link *tlink,
                      struct cifs_pending_open *open)
{
        spin_lock(&tlink_tcon(tlink)->open_file_lock);
        cifs_add_pending_open_locked(fid, tlink, open);
        spin_unlock(&tlink_tcon(open->tlink)->open_file_lock);
}

/* parses DFS refferal V3 structure
 * caller is responsible for freeing target_nodes
 * returns:
 * - on success - 0
 * - on failure - errno
 */
int
parse_dfs_referrals(struct get_dfs_referral_rsp *rsp, u32 rsp_size,
                    unsigned int *num_of_nodes,
                    struct dfs_info3_param **target_nodes,
                    const struct nls_table *nls_codepage, int remap,
                    const char *searchName, bool is_unicode)
{
        int i, rc = 0;
        char *data_end;
        struct dfs_referral_level_3 *ref;

        *num_of_nodes = le16_to_cpu(rsp->NumberOfReferrals);

        if (*num_of_nodes < 1) {
                cifs_dbg(VFS, "num_referrals: must be at least > 0, but we get num_referrals = %d\n",
                         *num_of_nodes);
                rc = -EINVAL;
                goto parse_DFS_referrals_exit;
        }

        ref = (struct dfs_referral_level_3 *) &(rsp->referrals);
        if (ref->VersionNumber != cpu_to_le16(3)) {
                cifs_dbg(VFS, "Referrals of V%d version are not supported, should be V3\n",
                         le16_to_cpu(ref->VersionNumber));
                rc = -EINVAL;
                goto parse_DFS_referrals_exit;
        }

        /* get the upper boundary of the resp buffer */
        data_end = (char *)rsp + rsp_size;

        cifs_dbg(FYI, "num_referrals: %d dfs flags: 0x%x ...\n",
                 *num_of_nodes, le32_to_cpu(rsp->DFSFlags));

        *target_nodes = kcalloc(*num_of_nodes, sizeof(struct dfs_info3_param),
                                GFP_KERNEL);
        if (*target_nodes == NULL) {
                rc = -ENOMEM;
                goto parse_DFS_referrals_exit;
        }

        /* collect necessary data from referrals */
        for (i = 0; i < *num_of_nodes; i++) {
                char *temp;
                int max_len;
                struct dfs_info3_param *node = (*target_nodes)+i;

                node->flags = le32_to_cpu(rsp->DFSFlags);
                if (is_unicode) {
                        __le16 *tmp = kmalloc(strlen(searchName)*2 + 2,
                                                GFP_KERNEL);
                        if (tmp == NULL) {
                                rc = -ENOMEM;
                                goto parse_DFS_referrals_exit;
                        }
                        cifsConvertToUTF16((__le16 *) tmp, searchName,
                                           PATH_MAX, nls_codepage, remap);
                        node->path_consumed = cifs_utf16_bytes(tmp,
                                        le16_to_cpu(rsp->PathConsumed),
                                        nls_codepage);
                        kfree(tmp);
                } else
                        node->path_consumed = le16_to_cpu(rsp->PathConsumed);

                node->server_type = le16_to_cpu(ref->ServerType);
                node->ref_flag = le16_to_cpu(ref->ReferralEntryFlags);

                /* copy DfsPath */
                temp = (char *)ref + le16_to_cpu(ref->DfsPathOffset);
                max_len = data_end - temp;
                node->path_name = cifs_strndup_from_utf16(temp, max_len,
                                                is_unicode, nls_codepage);
                if (!node->path_name) {
                        rc = -ENOMEM;
                        goto parse_DFS_referrals_exit;
                }

                /* copy link target UNC */
                temp = (char *)ref + le16_to_cpu(ref->NetworkAddressOffset);
                max_len = data_end - temp;
                node->node_name = cifs_strndup_from_utf16(temp, max_len,
                                                is_unicode, nls_codepage);
                if (!node->node_name) {
                        rc = -ENOMEM;
                        goto parse_DFS_referrals_exit;
                }

                ref++;
        }

parse_DFS_referrals_exit:
        if (rc) {
                free_dfs_info_array(*target_nodes, *num_of_nodes);
                *target_nodes = NULL;
                *num_of_nodes = 0;
        }
        return rc;
}

struct cifs_aio_ctx *
cifs_aio_ctx_alloc(void)
{
        struct cifs_aio_ctx *ctx;

        ctx = kzalloc(sizeof(struct cifs_aio_ctx), GFP_KERNEL);
        if (!ctx)
                return NULL;

        INIT_LIST_HEAD(&ctx->list);
        mutex_init(&ctx->aio_mutex);
        init_completion(&ctx->done);
        kref_init(&ctx->refcount);
        return ctx;
}

void
cifs_aio_ctx_release(struct kref *refcount)
{
        struct cifs_aio_ctx *ctx = container_of(refcount,
                                        struct cifs_aio_ctx, refcount);

        cifsFileInfo_put(ctx->cfile);
        kvfree(ctx->bv);
        kfree(ctx);
}

#define CIFS_AIO_KMALLOC_LIMIT (1024 * 1024)

int
setup_aio_ctx_iter(struct cifs_aio_ctx *ctx, struct iov_iter *iter, int rw)
{
        ssize_t rc;
        unsigned int cur_npages;
        unsigned int npages = 0;
        unsigned int i;
        size_t len;
        size_t count = iov_iter_count(iter);
        unsigned int saved_len;
        size_t start;
        unsigned int max_pages = iov_iter_npages(iter, INT_MAX);
        struct page **pages = NULL;
        struct bio_vec *bv = NULL;

        if (iter->type & ITER_KVEC) {
                memcpy(&ctx->iter, iter, sizeof(struct iov_iter));
                ctx->len = count;
                iov_iter_advance(iter, count);
                return 0;
        }

        if (max_pages * sizeof(struct bio_vec) <= CIFS_AIO_KMALLOC_LIMIT)
                bv = kmalloc_array(max_pages, sizeof(struct bio_vec),
                                   GFP_KERNEL);

        if (!bv) {
                bv = vmalloc(max_pages * sizeof(struct bio_vec));
                if (!bv)
                        return -ENOMEM;
        }

        if (max_pages * sizeof(struct page *) <= CIFS_AIO_KMALLOC_LIMIT)
                pages = kmalloc_array(max_pages, sizeof(struct page *),
                                      GFP_KERNEL);

        if (!pages) {
                pages = vmalloc(max_pages * sizeof(struct page *));
                if (!pages) {
                        kvfree(bv);
                        return -ENOMEM;
                }
        }

        saved_len = count;

        while (count && npages < max_pages) {
                rc = iov_iter_get_pages(iter, pages, count, max_pages, &start);
                if (rc < 0) {
                        cifs_dbg(VFS, "couldn't get user pages (rc=%zd)\n", rc);
                        break;
                }

                if (rc > count) {
                        cifs_dbg(VFS, "get pages rc=%zd more than %zu\n", rc,
                                 count);
                        break;
                }

                iov_iter_advance(iter, rc);
                count -= rc;
                rc += start;
                cur_npages = DIV_ROUND_UP(rc, PAGE_SIZE);

                if (npages + cur_npages > max_pages) {
                        cifs_dbg(VFS, "out of vec array capacity (%u vs %u)\n",
                                 npages + cur_npages, max_pages);
                        break;
                }

                for (i = 0; i < cur_npages; i++) {
                        len = rc > PAGE_SIZE ? PAGE_SIZE : rc;
                        bv[npages + i].bv_page = pages[i];
                        bv[npages + i].bv_offset = start;
                        bv[npages + i].bv_len = len - start;
                        rc -= len;
                        start = 0;
                }

                npages += cur_npages;
        }

        kvfree(pages);
        ctx->bv = bv;
        ctx->len = saved_len - count;
        ctx->npages = npages;
        iov_iter_bvec(&ctx->iter, ITER_BVEC | rw, ctx->bv, npages, ctx->len);
        return 0;
}