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[thirdparty/linux.git] / fs / xfs / xfs_dir2_readdir.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * Copyright (c) 2013 Red Hat, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_mount.h"
#include "xfs_da_format.h"
#include "xfs_da_btree.h"
#include "xfs_inode.h"
#include "xfs_dir2.h"
#include "xfs_dir2_priv.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_bmap.h"
#include "xfs_trans.h"

/*
 * Directory file type support functions
 */
static unsigned char xfs_dir3_filetype_table[] = {
        DT_UNKNOWN, DT_REG, DT_DIR, DT_CHR, DT_BLK,
        DT_FIFO, DT_SOCK, DT_LNK, DT_WHT,
};

static unsigned char
xfs_dir3_get_dtype(
        struct xfs_mount        *mp,
        __uint8_t               filetype)
{
        if (!xfs_sb_version_hasftype(&mp->m_sb))
                return DT_UNKNOWN;

        if (filetype >= XFS_DIR3_FT_MAX)
                return DT_UNKNOWN;

        return xfs_dir3_filetype_table[filetype];
}

STATIC int
xfs_dir2_sf_getdents(
        struct xfs_da_args      *args,
        struct dir_context      *ctx)
{
        int                     i;              /* shortform entry number */
        struct xfs_inode        *dp = args->dp; /* incore directory inode */
        xfs_dir2_dataptr_t      off;            /* current entry's offset */
        xfs_dir2_sf_entry_t     *sfep;          /* shortform directory entry */
        xfs_dir2_sf_hdr_t       *sfp;           /* shortform structure */
        xfs_dir2_dataptr_t      dot_offset;
        xfs_dir2_dataptr_t      dotdot_offset;
        xfs_ino_t               ino;
        struct xfs_da_geometry  *geo = args->geo;

        ASSERT(dp->i_df.if_flags & XFS_IFINLINE);
        ASSERT(dp->i_df.if_bytes == dp->i_d.di_size);
        ASSERT(dp->i_df.if_u1.if_data != NULL);

        sfp = (xfs_dir2_sf_hdr_t *)dp->i_df.if_u1.if_data;

        /*
         * If the block number in the offset is out of range, we're done.
         */
        if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
                return 0;

        /*
         * Precalculate offsets for . and .. as we will always need them.
         *
         * XXX(hch): the second argument is sometimes 0 and sometimes
         * geo->datablk
         */
        dot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
                                                dp->d_ops->data_dot_offset);
        dotdot_offset = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
                                                dp->d_ops->data_dotdot_offset);

        /*
         * Put . entry unless we're starting past it.
         */
        if (ctx->pos <= dot_offset) {
                ctx->pos = dot_offset & 0x7fffffff;
                if (!dir_emit(ctx, ".", 1, dp->i_ino, DT_DIR))
                        return 0;
        }

        /*
         * Put .. entry unless we're starting past it.
         */
        if (ctx->pos <= dotdot_offset) {
                ino = dp->d_ops->sf_get_parent_ino(sfp);
                ctx->pos = dotdot_offset & 0x7fffffff;
                if (!dir_emit(ctx, "..", 2, ino, DT_DIR))
                        return 0;
        }

        /*
         * Loop while there are more entries and put'ing works.
         */
        sfep = xfs_dir2_sf_firstentry(sfp);
        for (i = 0; i < sfp->count; i++) {
                __uint8_t filetype;

                off = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
                                xfs_dir2_sf_get_offset(sfep));

                if (ctx->pos > off) {
                        sfep = dp->d_ops->sf_nextentry(sfp, sfep);
                        continue;
                }

                ino = dp->d_ops->sf_get_ino(sfp, sfep);
                filetype = dp->d_ops->sf_get_ftype(sfep);
                ctx->pos = off & 0x7fffffff;
                if (!dir_emit(ctx, (char *)sfep->name, sfep->namelen, ino,
                            xfs_dir3_get_dtype(dp->i_mount, filetype)))
                        return 0;
                sfep = dp->d_ops->sf_nextentry(sfp, sfep);
        }

        ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
                                                                0x7fffffff;
        return 0;
}

/*
 * Readdir for block directories.
 */
STATIC int
xfs_dir2_block_getdents(
        struct xfs_da_args      *args,
        struct dir_context      *ctx)
{
        struct xfs_inode        *dp = args->dp; /* incore directory inode */
        xfs_dir2_data_hdr_t     *hdr;           /* block header */
        struct xfs_buf          *bp;            /* buffer for block */
        xfs_dir2_block_tail_t   *btp;           /* block tail */
        xfs_dir2_data_entry_t   *dep;           /* block data entry */
        xfs_dir2_data_unused_t  *dup;           /* block unused entry */
        char                    *endptr;        /* end of the data entries */
        int                     error;          /* error return value */
        char                    *ptr;           /* current data entry */
        int                     wantoff;        /* starting block offset */
        xfs_off_t               cook;
        struct xfs_da_geometry  *geo = args->geo;
        int                     lock_mode;

        /*
         * If the block number in the offset is out of range, we're done.
         */
        if (xfs_dir2_dataptr_to_db(geo, ctx->pos) > geo->datablk)
                return 0;

        lock_mode = xfs_ilock_data_map_shared(dp);
        error = xfs_dir3_block_read(NULL, dp, &bp);
        xfs_iunlock(dp, lock_mode);
        if (error)
                return error;

        /*
         * Extract the byte offset we start at from the seek pointer.
         * We'll skip entries before this.
         */
        wantoff = xfs_dir2_dataptr_to_off(geo, ctx->pos);
        hdr = bp->b_addr;
        xfs_dir3_data_check(dp, bp);
        /*
         * Set up values for the loop.
         */
        btp = xfs_dir2_block_tail_p(geo, hdr);
        ptr = (char *)dp->d_ops->data_entry_p(hdr);
        endptr = (char *)xfs_dir2_block_leaf_p(btp);

        /*
         * Loop over the data portion of the block.
         * Each object is a real entry (dep) or an unused one (dup).
         */
        while (ptr < endptr) {
                __uint8_t filetype;

                dup = (xfs_dir2_data_unused_t *)ptr;
                /*
                 * Unused, skip it.
                 */
                if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
                        ptr += be16_to_cpu(dup->length);
                        continue;
                }

                dep = (xfs_dir2_data_entry_t *)ptr;

                /*
                 * Bump pointer for the next iteration.
                 */
                ptr += dp->d_ops->data_entsize(dep->namelen);
                /*
                 * The entry is before the desired starting point, skip it.
                 */
                if ((char *)dep - (char *)hdr < wantoff)
                        continue;

                cook = xfs_dir2_db_off_to_dataptr(geo, geo->datablk,
                                            (char *)dep - (char *)hdr);

                ctx->pos = cook & 0x7fffffff;
                filetype = dp->d_ops->data_get_ftype(dep);
                /*
                 * If it didn't fit, set the final offset to here & return.
                 */
                if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
                            be64_to_cpu(dep->inumber),
                            xfs_dir3_get_dtype(dp->i_mount, filetype))) {
                        xfs_trans_brelse(NULL, bp);
                        return 0;
                }
        }

        /*
         * Reached the end of the block.
         * Set the offset to a non-existent block 1 and return.
         */
        ctx->pos = xfs_dir2_db_off_to_dataptr(geo, geo->datablk + 1, 0) &
                                                                0x7fffffff;
        xfs_trans_brelse(NULL, bp);
        return 0;
}

struct xfs_dir2_leaf_map_info {
        xfs_extlen_t    map_blocks;     /* number of fsbs in map */
        xfs_dablk_t     map_off;        /* last mapped file offset */
        int             map_size;       /* total entries in *map */
        int             map_valid;      /* valid entries in *map */
        int             nmap;           /* mappings to ask xfs_bmapi */
        xfs_dir2_db_t   curdb;          /* db for current block */
        int             ra_current;     /* number of read-ahead blks */
        int             ra_index;       /* *map index for read-ahead */
        int             ra_offset;      /* map entry offset for ra */
        int             ra_want;        /* readahead count wanted */
        struct xfs_bmbt_irec map[];     /* map vector for blocks */
};

STATIC int
xfs_dir2_leaf_readbuf(
        struct xfs_da_args      *args,
        size_t                  bufsize,
        struct xfs_dir2_leaf_map_info *mip,
        xfs_dir2_off_t          *curoff,
        struct xfs_buf          **bpp,
        bool                    trim_map)
{
        struct xfs_inode        *dp = args->dp;
        struct xfs_buf          *bp = NULL;
        struct xfs_bmbt_irec    *map = mip->map;
        struct blk_plug         plug;
        int                     error = 0;
        int                     length;
        int                     i;
        int                     j;
        struct xfs_da_geometry  *geo = args->geo;

        /*
         * If the caller just finished processing a buffer, it will tell us
         * we need to trim that block out of the mapping now it is done.
         */
        if (trim_map) {
                mip->map_blocks -= geo->fsbcount;
                /*
                 * Loop to get rid of the extents for the
                 * directory block.
                 */
                for (i = geo->fsbcount; i > 0; ) {
                        j = min_t(int, map->br_blockcount, i);
                        map->br_blockcount -= j;
                        map->br_startblock += j;
                        map->br_startoff += j;
                        /*
                         * If mapping is done, pitch it from
                         * the table.
                         */
                        if (!map->br_blockcount && --mip->map_valid)
                                memmove(&map[0], &map[1],
                                        sizeof(map[0]) * mip->map_valid);
                        i -= j;
                }
        }

        /*
         * Recalculate the readahead blocks wanted.
         */
        mip->ra_want = howmany(bufsize + geo->blksize, (1 << geo->fsblog)) - 1;
        ASSERT(mip->ra_want >= 0);

        /*
         * If we don't have as many as we want, and we haven't
         * run out of data blocks, get some more mappings.
         */
        if (1 + mip->ra_want > mip->map_blocks &&
            mip->map_off < xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET)) {
                /*
                 * Get more bmaps, fill in after the ones
                 * we already have in the table.
                 */
                mip->nmap = mip->map_size - mip->map_valid;
                error = xfs_bmapi_read(dp, mip->map_off,
                                xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET) -
                                                                mip->map_off,
                                &map[mip->map_valid], &mip->nmap, 0);

                /*
                 * Don't know if we should ignore this or try to return an
                 * error.  The trouble with returning errors is that readdir
                 * will just stop without actually passing the error through.
                 */
                if (error)
                        goto out;       /* XXX */

                /*
                 * If we got all the mappings we asked for, set the final map
                 * offset based on the last bmap value received.  Otherwise,
                 * we've reached the end.
                 */
                if (mip->nmap == mip->map_size - mip->map_valid) {
                        i = mip->map_valid + mip->nmap - 1;
                        mip->map_off = map[i].br_startoff + map[i].br_blockcount;
                } else
                        mip->map_off = xfs_dir2_byte_to_da(geo,
                                                        XFS_DIR2_LEAF_OFFSET);

                /*
                 * Look for holes in the mapping, and eliminate them.  Count up
                 * the valid blocks.
                 */
                for (i = mip->map_valid; i < mip->map_valid + mip->nmap; ) {
                        if (map[i].br_startblock == HOLESTARTBLOCK) {
                                mip->nmap--;
                                length = mip->map_valid + mip->nmap - i;
                                if (length)
                                        memmove(&map[i], &map[i + 1],
                                                sizeof(map[i]) * length);
                        } else {
                                mip->map_blocks += map[i].br_blockcount;
                                i++;
                        }
                }
                mip->map_valid += mip->nmap;
        }

        /*
         * No valid mappings, so no more data blocks.
         */
        if (!mip->map_valid) {
                *curoff = xfs_dir2_da_to_byte(geo, mip->map_off);
                goto out;
        }

        /*
         * Read the directory block starting at the first mapping.
         */
        mip->curdb = xfs_dir2_da_to_db(geo, map->br_startoff);
        error = xfs_dir3_data_read(NULL, dp, map->br_startoff,
                        map->br_blockcount >= geo->fsbcount ?
                            XFS_FSB_TO_DADDR(dp->i_mount, map->br_startblock) :
                            -1, &bp);
        /*
         * Should just skip over the data block instead of giving up.
         */
        if (error)
                goto out;       /* XXX */

        /*
         * Adjust the current amount of read-ahead: we just read a block that
         * was previously ra.
         */
        if (mip->ra_current)
                mip->ra_current -= geo->fsbcount;

        /*
         * Do we need more readahead?
         */
        blk_start_plug(&plug);
        for (mip->ra_index = mip->ra_offset = i = 0;
             mip->ra_want > mip->ra_current && i < mip->map_blocks;
             i += geo->fsbcount) {
                ASSERT(mip->ra_index < mip->map_valid);
                /*
                 * Read-ahead a contiguous directory block.
                 */
                if (i > mip->ra_current &&
                    map[mip->ra_index].br_blockcount >= geo->fsbcount) {
                        xfs_dir3_data_readahead(dp,
                                map[mip->ra_index].br_startoff + mip->ra_offset,
                                XFS_FSB_TO_DADDR(dp->i_mount,
                                        map[mip->ra_index].br_startblock +
                                                        mip->ra_offset));
                        mip->ra_current = i;
                }

                /*
                 * Read-ahead a non-contiguous directory block.  This doesn't
                 * use our mapping, but this is a very rare case.
                 */
                else if (i > mip->ra_current) {
                        xfs_dir3_data_readahead(dp,
                                        map[mip->ra_index].br_startoff +
                                                        mip->ra_offset, -1);
                        mip->ra_current = i;
                }

                /*
                 * Advance offset through the mapping table.
                 */
                for (j = 0; j < geo->fsbcount; j += length ) {
                        /*
                         * The rest of this extent but not more than a dir
                         * block.
                         */
                        length = min_t(int, geo->fsbcount,
                                        map[mip->ra_index].br_blockcount -
                                                        mip->ra_offset);
                        mip->ra_offset += length;

                        /*
                         * Advance to the next mapping if this one is used up.
                         */
                        if (mip->ra_offset == map[mip->ra_index].br_blockcount) {
                                mip->ra_offset = 0;
                                mip->ra_index++;
                        }
                }
        }
        blk_finish_plug(&plug);

out:
        *bpp = bp;
        return error;
}

/*
 * Getdents (readdir) for leaf and node directories.
 * This reads the data blocks only, so is the same for both forms.
 */
STATIC int
xfs_dir2_leaf_getdents(
        struct xfs_da_args      *args,
        struct dir_context      *ctx,
        size_t                  bufsize)
{
        struct xfs_inode        *dp = args->dp;
        struct xfs_buf          *bp = NULL;     /* data block buffer */
        xfs_dir2_data_hdr_t     *hdr;           /* data block header */
        xfs_dir2_data_entry_t   *dep;           /* data entry */
        xfs_dir2_data_unused_t  *dup;           /* unused entry */
        int                     error = 0;      /* error return value */
        int                     length;         /* temporary length value */
        int                     byteoff;        /* offset in current block */
        xfs_dir2_off_t          curoff;         /* current overall offset */
        xfs_dir2_off_t          newoff;         /* new curoff after new blk */
        char                    *ptr = NULL;    /* pointer to current data */
        struct xfs_dir2_leaf_map_info *map_info;
        struct xfs_da_geometry  *geo = args->geo;

        /*
         * If the offset is at or past the largest allowed value,
         * give up right away.
         */
        if (ctx->pos >= XFS_DIR2_MAX_DATAPTR)
                return 0;

        /*
         * Set up to bmap a number of blocks based on the caller's
         * buffer size, the directory block size, and the filesystem
         * block size.
         */
        length = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
        map_info = kmem_zalloc(offsetof(struct xfs_dir2_leaf_map_info, map) +
                                (length * sizeof(struct xfs_bmbt_irec)),
                               KM_SLEEP | KM_NOFS);
        map_info->map_size = length;

        /*
         * Inside the loop we keep the main offset value as a byte offset
         * in the directory file.
         */
        curoff = xfs_dir2_dataptr_to_byte(ctx->pos);

        /*
         * Force this conversion through db so we truncate the offset
         * down to get the start of the data block.
         */
        map_info->map_off = xfs_dir2_db_to_da(geo,
                                              xfs_dir2_byte_to_db(geo, curoff));

        /*
         * Loop over directory entries until we reach the end offset.
         * Get more blocks and readahead as necessary.
         */
        while (curoff < XFS_DIR2_LEAF_OFFSET) {
                __uint8_t filetype;

                /*
                 * If we have no buffer, or we're off the end of the
                 * current buffer, need to get another one.
                 */
                if (!bp || ptr >= (char *)bp->b_addr + geo->blksize) {
                        int     lock_mode;
                        bool    trim_map = false;

                        if (bp) {
                                xfs_trans_brelse(NULL, bp);
                                bp = NULL;
                                trim_map = true;
                        }

                        lock_mode = xfs_ilock_data_map_shared(dp);
                        error = xfs_dir2_leaf_readbuf(args, bufsize, map_info,
                                                      &curoff, &bp, trim_map);
                        xfs_iunlock(dp, lock_mode);
                        if (error || !map_info->map_valid)
                                break;

                        /*
                         * Having done a read, we need to set a new offset.
                         */
                        newoff = xfs_dir2_db_off_to_byte(geo,
                                                         map_info->curdb, 0);
                        /*
                         * Start of the current block.
                         */
                        if (curoff < newoff)
                                curoff = newoff;
                        /*
                         * Make sure we're in the right block.
                         */
                        else if (curoff > newoff)
                                ASSERT(xfs_dir2_byte_to_db(geo, curoff) ==
                                       map_info->curdb);
                        hdr = bp->b_addr;
                        xfs_dir3_data_check(dp, bp);
                        /*
                         * Find our position in the block.
                         */
                        ptr = (char *)dp->d_ops->data_entry_p(hdr);
                        byteoff = xfs_dir2_byte_to_off(geo, curoff);
                        /*
                         * Skip past the header.
                         */
                        if (byteoff == 0)
                                curoff += dp->d_ops->data_entry_offset;
                        /*
                         * Skip past entries until we reach our offset.
                         */
                        else {
                                while ((char *)ptr - (char *)hdr < byteoff) {
                                        dup = (xfs_dir2_data_unused_t *)ptr;

                                        if (be16_to_cpu(dup->freetag)
                                                  == XFS_DIR2_DATA_FREE_TAG) {

                                                length = be16_to_cpu(dup->length);
                                                ptr += length;
                                                continue;
                                        }
                                        dep = (xfs_dir2_data_entry_t *)ptr;
                                        length =
                                           dp->d_ops->data_entsize(dep->namelen);
                                        ptr += length;
                                }
                                /*
                                 * Now set our real offset.
                                 */
                                curoff =
                                        xfs_dir2_db_off_to_byte(geo,
                                            xfs_dir2_byte_to_db(geo, curoff),
                                            (char *)ptr - (char *)hdr);
                                if (ptr >= (char *)hdr + geo->blksize) {
                                        continue;
                                }
                        }
                }
                /*
                 * We have a pointer to an entry.
                 * Is it a live one?
                 */
                dup = (xfs_dir2_data_unused_t *)ptr;
                /*
                 * No, it's unused, skip over it.
                 */
                if (be16_to_cpu(dup->freetag) == XFS_DIR2_DATA_FREE_TAG) {
                        length = be16_to_cpu(dup->length);
                        ptr += length;
                        curoff += length;
                        continue;
                }

                dep = (xfs_dir2_data_entry_t *)ptr;
                length = dp->d_ops->data_entsize(dep->namelen);
                filetype = dp->d_ops->data_get_ftype(dep);

                ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
                if (!dir_emit(ctx, (char *)dep->name, dep->namelen,
                            be64_to_cpu(dep->inumber),
                            xfs_dir3_get_dtype(dp->i_mount, filetype)))
                        break;

                /*
                 * Advance to next entry in the block.
                 */
                ptr += length;
                curoff += length;
                /* bufsize may have just been a guess; don't go negative */
                bufsize = bufsize > length ? bufsize - length : 0;
        }

        /*
         * All done.  Set output offset value to current offset.
         */
        if (curoff > xfs_dir2_dataptr_to_byte(XFS_DIR2_MAX_DATAPTR))
                ctx->pos = XFS_DIR2_MAX_DATAPTR & 0x7fffffff;
        else
                ctx->pos = xfs_dir2_byte_to_dataptr(curoff) & 0x7fffffff;
        kmem_free(map_info);
        if (bp)
                xfs_trans_brelse(NULL, bp);
        return error;
}

/*
 * Read a directory.
 */
int
xfs_readdir(
        struct xfs_inode        *dp,
        struct dir_context      *ctx,
        size_t                  bufsize)
{
        struct xfs_da_args      args = { NULL };
        int                     rval;
        int                     v;

        trace_xfs_readdir(dp);

        if (XFS_FORCED_SHUTDOWN(dp->i_mount))
                return -EIO;

        ASSERT(S_ISDIR(VFS_I(dp)->i_mode));
        XFS_STATS_INC(dp->i_mount, xs_dir_getdents);

        args.dp = dp;
        args.geo = dp->i_mount->m_dir_geo;

        if (dp->i_d.di_format == XFS_DINODE_FMT_LOCAL)
                rval = xfs_dir2_sf_getdents(&args, ctx);
        else if ((rval = xfs_dir2_isblock(&args, &v)))
                ;
        else if (v)
                rval = xfs_dir2_block_getdents(&args, ctx);
        else
                rval = xfs_dir2_leaf_getdents(&args, ctx, bufsize);

        return rval;
}