mm: fix exec activate_mm vs TLB shootdown and lazy tlb switching race

[linux/fpc-iii.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(args->trans, 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(args->trans, 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(args->trans, bp);
        return 0;
}

/*
 * Read a directory block and initiate readahead for blocks beyond that.
 * We maintain a sliding readahead window of the remaining space in the
 * buffer rounded up to the nearest block.
 */
STATIC int
xfs_dir2_leaf_readbuf(
        struct xfs_da_args      *args,
        size_t                  bufsize,
        xfs_dir2_off_t          *cur_off,
        xfs_dablk_t             *ra_blk,
        struct xfs_buf          **bpp)
{
        struct xfs_inode        *dp = args->dp;
        struct xfs_buf          *bp = NULL;
        struct xfs_da_geometry  *geo = args->geo;
        struct xfs_ifork        *ifp = XFS_IFORK_PTR(dp, XFS_DATA_FORK);
        struct xfs_bmbt_irec    map;
        struct blk_plug         plug;
        xfs_dir2_off_t          new_off;
        xfs_dablk_t             next_ra;
        xfs_dablk_t             map_off;
        xfs_dablk_t             last_da;
        xfs_extnum_t            idx;
        int                     ra_want;
        int                     error = 0;

        if (!(ifp->if_flags & XFS_IFEXTENTS)) {
                error = xfs_iread_extents(args->trans, dp, XFS_DATA_FORK);
                if (error)
                        goto out;
        }

        /*
         * Look for mapped directory blocks at or above the current offset.
         * Truncate down to the nearest directory block to start the scanning
         * operation.
         */
        last_da = xfs_dir2_byte_to_da(geo, XFS_DIR2_LEAF_OFFSET);
        map_off = xfs_dir2_db_to_da(geo, xfs_dir2_byte_to_db(geo, *cur_off));
        if (!xfs_iext_lookup_extent(dp, ifp, map_off, &idx, &map))
                goto out;
        if (map.br_startoff >= last_da)
                goto out;
        xfs_trim_extent(&map, map_off, last_da - map_off);

        /* Read the directory block of that first mapping. */
        new_off = xfs_dir2_da_to_byte(geo, map.br_startoff);
        if (new_off > *cur_off)
                *cur_off = new_off;
        error = xfs_dir3_data_read(args->trans, dp, map.br_startoff, -1, &bp);
        if (error)
                goto out;

        /*
         * Start readahead for the next bufsize's worth of dir data blocks.
         * We may have already issued readahead for some of that range;
         * ra_blk tracks the last block we tried to read(ahead).
         */
        ra_want = howmany(bufsize + geo->blksize, (1 << geo->fsblog));
        if (*ra_blk >= last_da)
                goto out;
        else if (*ra_blk == 0)
                *ra_blk = map.br_startoff;
        next_ra = map.br_startoff + geo->fsbcount;
        if (next_ra >= last_da)
                goto out_no_ra;
        if (map.br_blockcount < geo->fsbcount &&
            !xfs_iext_get_extent(ifp, ++idx, &map))
                goto out_no_ra;
        if (map.br_startoff >= last_da)
                goto out_no_ra;
        xfs_trim_extent(&map, next_ra, last_da - next_ra);

        /* Start ra for each dir (not fs) block that has a mapping. */
        blk_start_plug(&plug);
        while (ra_want > 0) {
                next_ra = roundup((xfs_dablk_t)map.br_startoff, geo->fsbcount);
                while (ra_want > 0 &&
                       next_ra < map.br_startoff + map.br_blockcount) {
                        if (next_ra >= last_da) {
                                *ra_blk = last_da;
                                break;
                        }
                        if (next_ra > *ra_blk) {
                                xfs_dir3_data_readahead(dp, next_ra, -2);
                                *ra_blk = next_ra;
                        }
                        ra_want -= geo->fsbcount;
                        next_ra += geo->fsbcount;
                }
                if (!xfs_iext_get_extent(ifp, ++idx, &map)) {
                        *ra_blk = last_da;
                        break;
                }
        }
        blk_finish_plug(&plug);

out:
        *bpp = bp;
        return error;
out_no_ra:
        *ra_blk = last_da;
        goto out;
}

/*
 * 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 */
        char                    *ptr = NULL;    /* pointer to current data */
        struct xfs_da_geometry  *geo = args->geo;
        xfs_dablk_t             rablk = 0;      /* current readahead block */
        xfs_dir2_off_t          curoff;         /* current overall offset */
        int                     length;         /* temporary length value */
        int                     byteoff;        /* offset in current block */
        int                     lock_mode;
        int                     error = 0;      /* error return value */

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

        /*
         * 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);

        /*
         * 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) {
                        if (bp) {
                                xfs_trans_brelse(args->trans, bp);
                                bp = NULL;
                        }

                        lock_mode = xfs_ilock_data_map_shared(dp);
                        error = xfs_dir2_leaf_readbuf(args, bufsize, &curoff,
                                        &rablk, &bp);
                        xfs_iunlock(dp, lock_mode);
                        if (error || !bp)
                                break;

                        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;
        if (bp)
                xfs_trans_brelse(args->trans, bp);
        return error;
}

/*
 * Read a directory.
 *
 * If supplied, the transaction collects locked dir buffers to avoid
 * nested buffer deadlocks.  This function does not dirty the
 * transaction.  The caller should ensure that the inode is locked
 * before calling this function.
 */
int
xfs_readdir(
        struct xfs_trans        *tp,
        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;
        args.trans = tp;

        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;
}