linux/fs/xfs/xfs_dir2_readdir.c
Christoph Hellwig b2b1712a64 xfs: introduce the xfs_iext_cursor abstraction
Add a new xfs_iext_cursor structure to hide the direct extent map
index manipulations. In addition to the existing lookup/get/insert/
remove and update routines new primitives to get the first and last
extent cursor, as well as moving up and down by one extent are
provided.  Also new are convenience to increment/decrement the
cursor and retreive the new extent, as well as to peek into the
previous/next extent without updating the cursor and last but not
least a macro to iterate over all extents in a fork.

[darrick: rename for_each_iext to for_each_xfs_iext]

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2017-11-06 11:53:40 -08:00

544 lines
14 KiB
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,
};
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;
struct xfs_iext_cursor icur;
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, &icur, &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_next_extent(ifp, &icur, &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_next_extent(ifp, &icur, &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;
}