Btrfs: make sure the backref walker catches all refs to our extent

[deliverable/linux.git] / fs / cifs / readdir.c

/*
 *   fs/cifs/readdir.c
 *
 *   Directory search handling
 *
 *   Copyright (C) International Business Machines  Corp., 2004, 2008
 *   Copyright (C) Red Hat, Inc., 2011
 *   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/fs.h>
#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/stat.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsproto.h"
#include "cifs_unicode.h"
#include "cifs_debug.h"
#include "cifs_fs_sb.h"
#include "cifsfs.h"

/*
 * To be safe - for UCS to UTF-8 with strings loaded with the rare long
 * characters alloc more to account for such multibyte target UTF-8
 * characters.
 */
#define UNICODE_NAME_MAX ((4 * NAME_MAX) + 2)

#ifdef CONFIG_CIFS_DEBUG2
static void dump_cifs_file_struct(struct file *file, char *label)
{
        struct cifsFileInfo *cf;

        if (file) {
                cf = file->private_data;
                if (cf == NULL) {
                        cifs_dbg(FYI, "empty cifs private file data\n");
                        return;
                }
                if (cf->invalidHandle)
                        cifs_dbg(FYI, "invalid handle\n");
                if (cf->srch_inf.endOfSearch)
                        cifs_dbg(FYI, "end of search\n");
                if (cf->srch_inf.emptyDir)
                        cifs_dbg(FYI, "empty dir\n");
        }
}
#else
static inline void dump_cifs_file_struct(struct file *file, char *label)
{
}
#endif /* DEBUG2 */

/*
 * Attempt to preload the dcache with the results from the FIND_FIRST/NEXT
 *
 * Find the dentry that matches "name". If there isn't one, create one. If it's
 * a negative dentry or the uniqueid changed, then drop it and recreate it.
 */
static void
cifs_prime_dcache(struct dentry *parent, struct qstr *name,
                    struct cifs_fattr *fattr)
{
        struct dentry *dentry, *alias;
        struct inode *inode;
        struct super_block *sb = parent->d_inode->i_sb;
        struct cifs_sb_info *cifs_sb = CIFS_SB(sb);

        cifs_dbg(FYI, "%s: for %s\n", __func__, name->name);

        dentry = d_hash_and_lookup(parent, name);
        if (unlikely(IS_ERR(dentry)))
                return;

        if (dentry) {
                int err;

                inode = dentry->d_inode;
                if (inode) {
                        /*
                         * If we're generating inode numbers, then we don't
                         * want to clobber the existing one with the one that
                         * the readdir code created.
                         */
                        if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM))
                                fattr->cf_uniqueid = CIFS_I(inode)->uniqueid;

                        /* update inode in place if i_ino didn't change */
                        if (CIFS_I(inode)->uniqueid == fattr->cf_uniqueid) {
                                cifs_fattr_to_inode(inode, fattr);
                                goto out;
                        }
                }
                err = d_invalidate(dentry);
                dput(dentry);
                if (err)
                        return;
        }

        dentry = d_alloc(parent, name);
        if (!dentry)
                return;

        inode = cifs_iget(sb, fattr);
        if (!inode)
                goto out;

        alias = d_materialise_unique(dentry, inode);
        if (alias && !IS_ERR(alias))
                dput(alias);
out:
        dput(dentry);
}

/*
 * Is it possible that this directory might turn out to be a DFS referral
 * once we go to try and use it?
 */
static bool
cifs_dfs_is_possible(struct cifs_sb_info *cifs_sb)
{
#ifdef CONFIG_CIFS_DFS_UPCALL
        struct cifs_tcon *tcon = cifs_sb_master_tcon(cifs_sb);

        if (tcon->Flags & SMB_SHARE_IS_IN_DFS)
                return true;
#endif
        return false;
}

static void
cifs_fill_common_info(struct cifs_fattr *fattr, struct cifs_sb_info *cifs_sb)
{
        fattr->cf_uid = cifs_sb->mnt_uid;
        fattr->cf_gid = cifs_sb->mnt_gid;

        if (fattr->cf_cifsattrs & ATTR_DIRECTORY) {
                fattr->cf_mode = S_IFDIR | cifs_sb->mnt_dir_mode;
                fattr->cf_dtype = DT_DIR;
                /*
                 * Windows CIFS servers generally make DFS referrals look
                 * like directories in FIND_* responses with the reparse
                 * attribute flag also set (since DFS junctions are
                 * reparse points). We must revalidate at least these
                 * directory inodes before trying to use them (if
                 * they are DFS we will get PATH_NOT_COVERED back
                 * when queried directly and can then try to connect
                 * to the DFS target)
                 */
                if (cifs_dfs_is_possible(cifs_sb) &&
                    (fattr->cf_cifsattrs & ATTR_REPARSE))
                        fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
        } else {
                fattr->cf_mode = S_IFREG | cifs_sb->mnt_file_mode;
                fattr->cf_dtype = DT_REG;
        }

        if (fattr->cf_cifsattrs & ATTR_READONLY)
                fattr->cf_mode &= ~S_IWUGO;

        /*
         * We of course don't get ACL info in FIND_FIRST/NEXT results, so
         * mark it for revalidation so that "ls -l" will look right. It might
         * be super-slow, but if we don't do this then the ownership of files
         * may look wrong since the inodes may not have timed out by the time
         * "ls" does a stat() call on them.
         */
        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_CIFS_ACL)
                fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;

        if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_UNX_EMUL &&
            fattr->cf_cifsattrs & ATTR_SYSTEM) {
                if (fattr->cf_eof == 0)  {
                        fattr->cf_mode &= ~S_IFMT;
                        fattr->cf_mode |= S_IFIFO;
                        fattr->cf_dtype = DT_FIFO;
                } else {
                        /*
                         * trying to get the type and mode via SFU can be slow,
                         * so just call those regular files for now, and mark
                         * for reval
                         */
                        fattr->cf_flags |= CIFS_FATTR_NEED_REVAL;
                }
        }
}

void
cifs_dir_info_to_fattr(struct cifs_fattr *fattr, FILE_DIRECTORY_INFO *info,
                       struct cifs_sb_info *cifs_sb)
{
        memset(fattr, 0, sizeof(*fattr));
        fattr->cf_cifsattrs = le32_to_cpu(info->ExtFileAttributes);
        fattr->cf_eof = le64_to_cpu(info->EndOfFile);
        fattr->cf_bytes = le64_to_cpu(info->AllocationSize);
        fattr->cf_createtime = le64_to_cpu(info->CreationTime);
        fattr->cf_atime = cifs_NTtimeToUnix(info->LastAccessTime);
        fattr->cf_ctime = cifs_NTtimeToUnix(info->ChangeTime);
        fattr->cf_mtime = cifs_NTtimeToUnix(info->LastWriteTime);

        cifs_fill_common_info(fattr, cifs_sb);
}

static void
cifs_std_info_to_fattr(struct cifs_fattr *fattr, FIND_FILE_STANDARD_INFO *info,
                       struct cifs_sb_info *cifs_sb)
{
        int offset = cifs_sb_master_tcon(cifs_sb)->ses->server->timeAdj;

        memset(fattr, 0, sizeof(*fattr));
        fattr->cf_atime = cnvrtDosUnixTm(info->LastAccessDate,
                                            info->LastAccessTime, offset);
        fattr->cf_ctime = cnvrtDosUnixTm(info->LastWriteDate,
                                            info->LastWriteTime, offset);
        fattr->cf_mtime = cnvrtDosUnixTm(info->LastWriteDate,
                                            info->LastWriteTime, offset);

        fattr->cf_cifsattrs = le16_to_cpu(info->Attributes);
        fattr->cf_bytes = le32_to_cpu(info->AllocationSize);
        fattr->cf_eof = le32_to_cpu(info->DataSize);

        cifs_fill_common_info(fattr, cifs_sb);
}

/* BB eventually need to add the following helper function to
      resolve NT_STATUS_STOPPED_ON_SYMLINK return code when
      we try to do FindFirst on (NTFS) directory symlinks */
/*
int get_symlink_reparse_path(char *full_path, struct cifs_sb_info *cifs_sb,
                             unsigned int xid)
{
        __u16 fid;
        int len;
        int oplock = 0;
        int rc;
        struct cifs_tcon *ptcon = cifs_sb_tcon(cifs_sb);
        char *tmpbuffer;

        rc = CIFSSMBOpen(xid, ptcon, full_path, FILE_OPEN, GENERIC_READ,
                        OPEN_REPARSE_POINT, &fid, &oplock, NULL,
                        cifs_sb->local_nls,
                        cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MAP_SPECIAL_CHR);
        if (!rc) {
                tmpbuffer = kmalloc(maxpath);
                rc = CIFSSMBQueryReparseLinkInfo(xid, ptcon, full_path,
                                tmpbuffer,
                                maxpath -1,
                                fid,
                                cifs_sb->local_nls);
                if (CIFSSMBClose(xid, ptcon, fid)) {
                        cifs_dbg(FYI, "Error closing temporary reparsepoint open\n");
                }
        }
}
 */

static int
initiate_cifs_search(const unsigned int xid, struct file *file)
{
        __u16 search_flags;
        int rc = 0;
        char *full_path = NULL;
        struct cifsFileInfo *cifsFile;
        struct cifs_sb_info *cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
        struct tcon_link *tlink = NULL;
        struct cifs_tcon *tcon;
        struct TCP_Server_Info *server;

        if (file->private_data == NULL) {
                tlink = cifs_sb_tlink(cifs_sb);
                if (IS_ERR(tlink))
                        return PTR_ERR(tlink);

                cifsFile = kzalloc(sizeof(struct cifsFileInfo), GFP_KERNEL);
                if (cifsFile == NULL) {
                        rc = -ENOMEM;
                        goto error_exit;
                }
                file->private_data = cifsFile;
                cifsFile->tlink = cifs_get_tlink(tlink);
                tcon = tlink_tcon(tlink);
        } else {
                cifsFile = file->private_data;
                tcon = tlink_tcon(cifsFile->tlink);
        }

        server = tcon->ses->server;

        if (!server->ops->query_dir_first) {
                rc = -ENOSYS;
                goto error_exit;
        }

        cifsFile->invalidHandle = true;
        cifsFile->srch_inf.endOfSearch = false;

        full_path = build_path_from_dentry(file->f_path.dentry);
        if (full_path == NULL) {
                rc = -ENOMEM;
                goto error_exit;
        }

        cifs_dbg(FYI, "Full path: %s start at: %lld\n", full_path, file->f_pos);

ffirst_retry:
        /* test for Unix extensions */
        /* but now check for them on the share/mount not on the SMB session */
        /* if (cap_unix(tcon->ses) { */
        if (tcon->unix_ext)
                cifsFile->srch_inf.info_level = SMB_FIND_FILE_UNIX;
        else if ((tcon->ses->capabilities &
                  tcon->ses->server->vals->cap_nt_find) == 0) {
                cifsFile->srch_inf.info_level = SMB_FIND_FILE_INFO_STANDARD;
        } else if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM) {
                cifsFile->srch_inf.info_level = SMB_FIND_FILE_ID_FULL_DIR_INFO;
        } else /* not srvinos - BB fixme add check for backlevel? */ {
                cifsFile->srch_inf.info_level = SMB_FIND_FILE_DIRECTORY_INFO;
        }

        search_flags = CIFS_SEARCH_CLOSE_AT_END | CIFS_SEARCH_RETURN_RESUME;
        if (backup_cred(cifs_sb))
                search_flags |= CIFS_SEARCH_BACKUP_SEARCH;

        rc = server->ops->query_dir_first(xid, tcon, full_path, cifs_sb,
                                          &cifsFile->fid, search_flags,
                                          &cifsFile->srch_inf);

        if (rc == 0)
                cifsFile->invalidHandle = false;
        /* BB add following call to handle readdir on new NTFS symlink errors
        else if STATUS_STOPPED_ON_SYMLINK
                call get_symlink_reparse_path and retry with new path */
        else if ((rc == -EOPNOTSUPP) &&
                (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM)) {
                cifs_sb->mnt_cifs_flags &= ~CIFS_MOUNT_SERVER_INUM;
                goto ffirst_retry;
        }
error_exit:
        kfree(full_path);
        cifs_put_tlink(tlink);
        return rc;
}

/* return length of unicode string in bytes */
static int cifs_unicode_bytelen(const char *str)
{
        int len;
        const __le16 *ustr = (const __le16 *)str;

        for (len = 0; len <= PATH_MAX; len++) {
                if (ustr[len] == 0)
                        return len << 1;
        }
        cifs_dbg(FYI, "Unicode string longer than PATH_MAX found\n");
        return len << 1;
}

static char *nxt_dir_entry(char *old_entry, char *end_of_smb, int level)
{
        char *new_entry;
        FILE_DIRECTORY_INFO *pDirInfo = (FILE_DIRECTORY_INFO *)old_entry;

        if (level == SMB_FIND_FILE_INFO_STANDARD) {
                FIND_FILE_STANDARD_INFO *pfData;
                pfData = (FIND_FILE_STANDARD_INFO *)pDirInfo;

                new_entry = old_entry + sizeof(FIND_FILE_STANDARD_INFO) +
                                pfData->FileNameLength;
        } else
                new_entry = old_entry + le32_to_cpu(pDirInfo->NextEntryOffset);
        cifs_dbg(FYI, "new entry %p old entry %p\n", new_entry, old_entry);
        /* validate that new_entry is not past end of SMB */
        if (new_entry >= end_of_smb) {
                cifs_dbg(VFS, "search entry %p began after end of SMB %p old entry %p\n",
                         new_entry, end_of_smb, old_entry);
                return NULL;
        } else if (((level == SMB_FIND_FILE_INFO_STANDARD) &&
                    (new_entry + sizeof(FIND_FILE_STANDARD_INFO) > end_of_smb))
                  || ((level != SMB_FIND_FILE_INFO_STANDARD) &&
                   (new_entry + sizeof(FILE_DIRECTORY_INFO) > end_of_smb)))  {
                cifs_dbg(VFS, "search entry %p extends after end of SMB %p\n",
                         new_entry, end_of_smb);
                return NULL;
        } else
                return new_entry;

}

struct cifs_dirent {
        const char      *name;
        size_t          namelen;
        u32             resume_key;
        u64             ino;
};

static void cifs_fill_dirent_unix(struct cifs_dirent *de,
                const FILE_UNIX_INFO *info, bool is_unicode)
{
        de->name = &info->FileName[0];
        if (is_unicode)
                de->namelen = cifs_unicode_bytelen(de->name);
        else
                de->namelen = strnlen(de->name, PATH_MAX);
        de->resume_key = info->ResumeKey;
        de->ino = le64_to_cpu(info->basic.UniqueId);
}

static void cifs_fill_dirent_dir(struct cifs_dirent *de,
                const FILE_DIRECTORY_INFO *info)
{
        de->name = &info->FileName[0];
        de->namelen = le32_to_cpu(info->FileNameLength);
        de->resume_key = info->FileIndex;
}

static void cifs_fill_dirent_full(struct cifs_dirent *de,
                const FILE_FULL_DIRECTORY_INFO *info)
{
        de->name = &info->FileName[0];
        de->namelen = le32_to_cpu(info->FileNameLength);
        de->resume_key = info->FileIndex;
}

static void cifs_fill_dirent_search(struct cifs_dirent *de,
                const SEARCH_ID_FULL_DIR_INFO *info)
{
        de->name = &info->FileName[0];
        de->namelen = le32_to_cpu(info->FileNameLength);
        de->resume_key = info->FileIndex;
        de->ino = le64_to_cpu(info->UniqueId);
}

static void cifs_fill_dirent_both(struct cifs_dirent *de,
                const FILE_BOTH_DIRECTORY_INFO *info)
{
        de->name = &info->FileName[0];
        de->namelen = le32_to_cpu(info->FileNameLength);
        de->resume_key = info->FileIndex;
}

static void cifs_fill_dirent_std(struct cifs_dirent *de,
                const FIND_FILE_STANDARD_INFO *info)
{
        de->name = &info->FileName[0];
        /* one byte length, no endianess conversion */
        de->namelen = info->FileNameLength;
        de->resume_key = info->ResumeKey;
}

static int cifs_fill_dirent(struct cifs_dirent *de, const void *info,
                u16 level, bool is_unicode)
{
        memset(de, 0, sizeof(*de));

        switch (level) {
        case SMB_FIND_FILE_UNIX:
                cifs_fill_dirent_unix(de, info, is_unicode);
                break;
        case SMB_FIND_FILE_DIRECTORY_INFO:
                cifs_fill_dirent_dir(de, info);
                break;
        case SMB_FIND_FILE_FULL_DIRECTORY_INFO:
                cifs_fill_dirent_full(de, info);
                break;
        case SMB_FIND_FILE_ID_FULL_DIR_INFO:
                cifs_fill_dirent_search(de, info);
                break;
        case SMB_FIND_FILE_BOTH_DIRECTORY_INFO:
                cifs_fill_dirent_both(de, info);
                break;
        case SMB_FIND_FILE_INFO_STANDARD:
                cifs_fill_dirent_std(de, info);
                break;
        default:
                cifs_dbg(FYI, "Unknown findfirst level %d\n", level);
                return -EINVAL;
        }

        return 0;
}

#define UNICODE_DOT cpu_to_le16(0x2e)

/* return 0 if no match and 1 for . (current directory) and 2 for .. (parent) */
static int cifs_entry_is_dot(struct cifs_dirent *de, bool is_unicode)
{
        int rc = 0;

        if (!de->name)
                return 0;

        if (is_unicode) {
                __le16 *ufilename = (__le16 *)de->name;
                if (de->namelen == 2) {
                        /* check for . */
                        if (ufilename[0] == UNICODE_DOT)
                                rc = 1;
                } else if (de->namelen == 4) {
                        /* check for .. */
                        if (ufilename[0] == UNICODE_DOT &&
                            ufilename[1] == UNICODE_DOT)
                                rc = 2;
                }
        } else /* ASCII */ {
                if (de->namelen == 1) {
                        if (de->name[0] == '.')
                                rc = 1;
                } else if (de->namelen == 2) {
                        if (de->name[0] == '.' && de->name[1] == '.')
                                rc = 2;
                }
        }

        return rc;
}

/* Check if directory that we are searching has changed so we can decide
   whether we can use the cached search results from the previous search */
static int is_dir_changed(struct file *file)
{
        struct inode *inode = file_inode(file);
        struct cifsInodeInfo *cifsInfo = CIFS_I(inode);

        if (cifsInfo->time == 0)
                return 1; /* directory was changed, perhaps due to unlink */
        else
                return 0;

}

static int cifs_save_resume_key(const char *current_entry,
        struct cifsFileInfo *file_info)
{
        struct cifs_dirent de;
        int rc;

        rc = cifs_fill_dirent(&de, current_entry, file_info->srch_inf.info_level,
                              file_info->srch_inf.unicode);
        if (!rc) {
                file_info->srch_inf.presume_name = de.name;
                file_info->srch_inf.resume_name_len = de.namelen;
                file_info->srch_inf.resume_key = de.resume_key;
        }
        return rc;
}

/*
 * Find the corresponding entry in the search. Note that the SMB server returns
 * search entries for . and .. which complicates logic here if we choose to
 * parse for them and we do not assume that they are located in the findfirst
 * return buffer. We start counting in the buffer with entry 2 and increment for
 * every entry (do not increment for . or .. entry).
 */
static int
find_cifs_entry(const unsigned int xid, struct cifs_tcon *tcon, loff_t pos,
                struct file *file, char **current_entry, int *num_to_ret)
{
        __u16 search_flags;
        int rc = 0;
        int pos_in_buf = 0;
        loff_t first_entry_in_buffer;
        loff_t index_to_find = pos;
        struct cifsFileInfo *cfile = file->private_data;
        struct cifs_sb_info *cifs_sb = CIFS_SB(file->f_path.dentry->d_sb);
        struct TCP_Server_Info *server = tcon->ses->server;
        /* check if index in the buffer */

        if (!server->ops->query_dir_first || !server->ops->query_dir_next)
                return -ENOSYS;

        if ((cfile == NULL) || (current_entry == NULL) || (num_to_ret == NULL))
                return -ENOENT;

        *current_entry = NULL;
        first_entry_in_buffer = cfile->srch_inf.index_of_last_entry -
                                        cfile->srch_inf.entries_in_buffer;

        /*
         * If first entry in buf is zero then is first buffer
         * in search response data which means it is likely . and ..
         * will be in this buffer, although some servers do not return
         * . and .. for the root of a drive and for those we need
         * to start two entries earlier.
         */

        dump_cifs_file_struct(file, "In fce ");
        if (((index_to_find < cfile->srch_inf.index_of_last_entry) &&
             is_dir_changed(file)) || (index_to_find < first_entry_in_buffer)) {
                /* close and restart search */
                cifs_dbg(FYI, "search backing up - close and restart search\n");
                spin_lock(&cifs_file_list_lock);
                if (!cfile->srch_inf.endOfSearch && !cfile->invalidHandle) {
                        cfile->invalidHandle = true;
                        spin_unlock(&cifs_file_list_lock);
                        if (server->ops->close)
                                server->ops->close(xid, tcon, &cfile->fid);
                } else
                        spin_unlock(&cifs_file_list_lock);
                if (cfile->srch_inf.ntwrk_buf_start) {
                        cifs_dbg(FYI, "freeing SMB ff cache buf on search rewind\n");
                        if (cfile->srch_inf.smallBuf)
                                cifs_small_buf_release(cfile->srch_inf.
                                                ntwrk_buf_start);
                        else
                                cifs_buf_release(cfile->srch_inf.
                                                ntwrk_buf_start);
                        cfile->srch_inf.ntwrk_buf_start = NULL;
                }
                rc = initiate_cifs_search(xid, file);
                if (rc) {
                        cifs_dbg(FYI, "error %d reinitiating a search on rewind\n",
                                 rc);
                        return rc;
                }
                /* FindFirst/Next set last_entry to NULL on malformed reply */
                if (cfile->srch_inf.last_entry)
                        cifs_save_resume_key(cfile->srch_inf.last_entry, cfile);
        }

        search_flags = CIFS_SEARCH_CLOSE_AT_END | CIFS_SEARCH_RETURN_RESUME;
        if (backup_cred(cifs_sb))
                search_flags |= CIFS_SEARCH_BACKUP_SEARCH;

        while ((index_to_find >= cfile->srch_inf.index_of_last_entry) &&
               (rc == 0) && !cfile->srch_inf.endOfSearch) {
                cifs_dbg(FYI, "calling findnext2\n");
                rc = server->ops->query_dir_next(xid, tcon, &cfile->fid,
                                                 search_flags,
                                                 &cfile->srch_inf);
                /* FindFirst/Next set last_entry to NULL on malformed reply */
                if (cfile->srch_inf.last_entry)
                        cifs_save_resume_key(cfile->srch_inf.last_entry, cfile);
                if (rc)
                        return -ENOENT;
        }
        if (index_to_find < cfile->srch_inf.index_of_last_entry) {
                /* we found the buffer that contains the entry */
                /* scan and find it */
                int i;
                char *cur_ent;
                char *end_of_smb = cfile->srch_inf.ntwrk_buf_start +
                        server->ops->calc_smb_size(
                                        cfile->srch_inf.ntwrk_buf_start);

                cur_ent = cfile->srch_inf.srch_entries_start;
                first_entry_in_buffer = cfile->srch_inf.index_of_last_entry
                                        - cfile->srch_inf.entries_in_buffer;
                pos_in_buf = index_to_find - first_entry_in_buffer;
                cifs_dbg(FYI, "found entry - pos_in_buf %d\n", pos_in_buf);

                for (i = 0; (i < (pos_in_buf)) && (cur_ent != NULL); i++) {
                        /* go entry by entry figuring out which is first */
                        cur_ent = nxt_dir_entry(cur_ent, end_of_smb,
                                                cfile->srch_inf.info_level);
                }
                if ((cur_ent == NULL) && (i < pos_in_buf)) {
                        /* BB fixme - check if we should flag this error */
                        cifs_dbg(VFS, "reached end of buf searching for pos in buf %d index to find %lld rc %d\n",
                                 pos_in_buf, index_to_find, rc);
                }
                rc = 0;
                *current_entry = cur_ent;
        } else {
                cifs_dbg(FYI, "index not in buffer - could not findnext into it\n");
                return 0;
        }

        if (pos_in_buf >= cfile->srch_inf.entries_in_buffer) {
                cifs_dbg(FYI, "can not return entries pos_in_buf beyond last\n");
                *num_to_ret = 0;
        } else
                *num_to_ret = cfile->srch_inf.entries_in_buffer - pos_in_buf;

        return rc;
}

static int cifs_filldir(char *find_entry, struct file *file,
                struct dir_context *ctx,
                char *scratch_buf, unsigned int max_len)
{
        struct cifsFileInfo *file_info = file->private_data;
        struct super_block *sb = file->f_path.dentry->d_sb;
        struct cifs_sb_info *cifs_sb = CIFS_SB(sb);
        struct cifs_dirent de = { NULL, };
        struct cifs_fattr fattr;
        struct qstr name;
        int rc = 0;
        ino_t ino;

        rc = cifs_fill_dirent(&de, find_entry, file_info->srch_inf.info_level,
                              file_info->srch_inf.unicode);
        if (rc)
                return rc;

        if (de.namelen > max_len) {
                cifs_dbg(VFS, "bad search response length %zd past smb end\n",
                         de.namelen);
                return -EINVAL;
        }

        /* skip . and .. since we added them first */
        if (cifs_entry_is_dot(&de, file_info->srch_inf.unicode))
                return 0;

        if (file_info->srch_inf.unicode) {
                struct nls_table *nlt = cifs_sb->local_nls;

                name.name = scratch_buf;
                name.len =
                        cifs_from_utf16((char *)name.name, (__le16 *)de.name,
                                        UNICODE_NAME_MAX,
                                        min_t(size_t, de.namelen,
                                              (size_t)max_len), nlt,
                                        cifs_sb->mnt_cifs_flags &
                                                CIFS_MOUNT_MAP_SPECIAL_CHR);
                name.len -= nls_nullsize(nlt);
        } else {
                name.name = de.name;
                name.len = de.namelen;
        }

        switch (file_info->srch_inf.info_level) {
        case SMB_FIND_FILE_UNIX:
                cifs_unix_basic_to_fattr(&fattr,
                                         &((FILE_UNIX_INFO *)find_entry)->basic,
                                         cifs_sb);
                break;
        case SMB_FIND_FILE_INFO_STANDARD:
                cifs_std_info_to_fattr(&fattr,
                                       (FIND_FILE_STANDARD_INFO *)find_entry,
                                       cifs_sb);
                break;
        default:
                cifs_dir_info_to_fattr(&fattr,
                                       (FILE_DIRECTORY_INFO *)find_entry,
                                       cifs_sb);
                break;
        }

        if (de.ino && (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_SERVER_INUM)) {
                fattr.cf_uniqueid = de.ino;
        } else {
                fattr.cf_uniqueid = iunique(sb, ROOT_I);
                cifs_autodisable_serverino(cifs_sb);
        }

        if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS) &&
            CIFSCouldBeMFSymlink(&fattr))
                /*
                 * trying to get the type and mode can be slow,
                 * so just call those regular files for now, and mark
                 * for reval
                 */
                fattr.cf_flags |= CIFS_FATTR_NEED_REVAL;

        cifs_prime_dcache(file->f_dentry, &name, &fattr);

        ino = cifs_uniqueid_to_ino_t(fattr.cf_uniqueid);
        return !dir_emit(ctx, name.name, name.len, ino, fattr.cf_dtype);
}


int cifs_readdir(struct file *file, struct dir_context *ctx)
{
        int rc = 0;
        unsigned int xid;
        int i;
        struct cifs_tcon *tcon;
        struct cifsFileInfo *cifsFile = NULL;
        char *current_entry;
        int num_to_fill = 0;
        char *tmp_buf = NULL;
        char *end_of_smb;
        unsigned int max_len;

        xid = get_xid();

        /*
         * Ensure FindFirst doesn't fail before doing filldir() for '.' and
         * '..'. Otherwise we won't be able to notify VFS in case of failure.
         */
        if (file->private_data == NULL) {
                rc = initiate_cifs_search(xid, file);
                cifs_dbg(FYI, "initiate cifs search rc %d\n", rc);
                if (rc)
                        goto rddir2_exit;
        }

        if (!dir_emit_dots(file, ctx))
                goto rddir2_exit;

        /* 1) If search is active,
                is in current search buffer?
                if it before then restart search
                if after then keep searching till find it */

        if (file->private_data == NULL) {
                rc = -EINVAL;
                goto rddir2_exit;
        }
        cifsFile = file->private_data;
        if (cifsFile->srch_inf.endOfSearch) {
                if (cifsFile->srch_inf.emptyDir) {
                        cifs_dbg(FYI, "End of search, empty dir\n");
                        rc = 0;
                        goto rddir2_exit;
                }
        } /* else {
                cifsFile->invalidHandle = true;
                tcon->ses->server->close(xid, tcon, &cifsFile->fid);
        } */

        tcon = tlink_tcon(cifsFile->tlink);
        rc = find_cifs_entry(xid, tcon, ctx->pos, file, &current_entry,
                             &num_to_fill);
        if (rc) {
                cifs_dbg(FYI, "fce error %d\n", rc);
                goto rddir2_exit;
        } else if (current_entry != NULL) {
                cifs_dbg(FYI, "entry %lld found\n", ctx->pos);
        } else {
                cifs_dbg(FYI, "could not find entry\n");
                goto rddir2_exit;
        }
        cifs_dbg(FYI, "loop through %d times filling dir for net buf %p\n",
                 num_to_fill, cifsFile->srch_inf.ntwrk_buf_start);
        max_len = tcon->ses->server->ops->calc_smb_size(
                        cifsFile->srch_inf.ntwrk_buf_start);
        end_of_smb = cifsFile->srch_inf.ntwrk_buf_start + max_len;

        tmp_buf = kmalloc(UNICODE_NAME_MAX, GFP_KERNEL);
        if (tmp_buf == NULL) {
                rc = -ENOMEM;
                goto rddir2_exit;
        }

        for (i = 0; i < num_to_fill; i++) {
                if (current_entry == NULL) {
                        /* evaluate whether this case is an error */
                        cifs_dbg(VFS, "past SMB end,  num to fill %d i %d\n",
                                 num_to_fill, i);
                        break;
                }
                /*
                 * if buggy server returns . and .. late do we want to
                 * check for that here?
                 */
                rc = cifs_filldir(current_entry, file, ctx,
                                  tmp_buf, max_len);
                if (rc) {
                        if (rc > 0)
                                rc = 0;
                        break;
                }

                ctx->pos++;
                if (ctx->pos ==
                        cifsFile->srch_inf.index_of_last_entry) {
                        cifs_dbg(FYI, "last entry in buf at pos %lld %s\n",
                                 ctx->pos, tmp_buf);
                        cifs_save_resume_key(current_entry, cifsFile);
                        break;
                } else
                        current_entry =
                                nxt_dir_entry(current_entry, end_of_smb,
                                        cifsFile->srch_inf.info_level);
        }
        kfree(tmp_buf);

rddir2_exit:
        free_xid(xid);
        return rc;
}