From: Dave Chinner <dchinner@xxxxxxxxxx> Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx> --- include/xfs_ag.h | 54 ++++++++++++- include/xfs_buf_item.h | 8 +- libxfs/xfs_alloc.c | 197 ++++++++++++++++++++++++++++++++---------------- libxfs/xfs_ialloc.c | 55 ++++++++++---- 4 files changed, 231 insertions(+), 83 deletions(-) diff --git a/include/xfs_ag.h b/include/xfs_ag.h index f2aeedb..1e0fa34 100644 --- a/include/xfs_ag.h +++ b/include/xfs_ag.h @@ -30,6 +30,7 @@ struct xfs_trans; #define XFS_AGF_MAGIC 0x58414746 /* 'XAGF' */ #define XFS_AGI_MAGIC 0x58414749 /* 'XAGI' */ +#define XFS_AGFL_MAGIC 0x5841464c /* 'XAFL' */ #define XFS_AGF_VERSION 1 #define XFS_AGI_VERSION 1 @@ -63,12 +64,29 @@ typedef struct xfs_agf { __be32 agf_spare0; /* spare field */ __be32 agf_levels[XFS_BTNUM_AGF]; /* btree levels */ __be32 agf_spare1; /* spare field */ + __be32 agf_flfirst; /* first freelist block's index */ __be32 agf_fllast; /* last freelist block's index */ __be32 agf_flcount; /* count of blocks in freelist */ __be32 agf_freeblks; /* total free blocks */ + __be32 agf_longest; /* longest free space */ __be32 agf_btreeblks; /* # of blocks held in AGF btrees */ + uuid_t agf_uuid; /* uuid of filesystem */ + + /* + * reserve some contiguous space for future logged fields before we add + * the unlogged fields. This makes the range logging via flags and + * structure offsets much simpler. + */ + __be64 agf_spare64[16]; + + /* unlogged fields, written during buffer writeback. */ + __be64 agf_lsn; /* last write sequence */ + __be32 agf_crc; /* crc of agf sector */ + __be32 agf_spare2; + + /* structure must be padded to 64 bit alignment */ } xfs_agf_t; #define XFS_AGF_MAGICNUM 0x00000001 @@ -83,6 +101,7 @@ typedef struct xfs_agf { #define XFS_AGF_FREEBLKS 0x00000200 #define XFS_AGF_LONGEST 0x00000400 #define XFS_AGF_BTREEBLKS 0x00000800 +#define XFS_AGF_UUID 0x00001000 #define XFS_AGF_NUM_BITS 12 #define XFS_AGF_ALL_BITS ((1 << XFS_AGF_NUM_BITS) - 1) @@ -98,7 +117,8 @@ typedef struct xfs_agf { { XFS_AGF_FLCOUNT, "FLCOUNT" }, \ { XFS_AGF_FREEBLKS, "FREEBLKS" }, \ { XFS_AGF_LONGEST, "LONGEST" }, \ - { XFS_AGF_BTREEBLKS, "BTREEBLKS" } + { XFS_AGF_BTREEBLKS, "BTREEBLKS" }, \ + { XFS_AGF_UUID, "UUID" } /* disk block (xfs_daddr_t) in the AG */ #define XFS_AGF_DADDR(mp) ((xfs_daddr_t)(1 << (mp)->m_sectbb_log)) @@ -132,6 +152,7 @@ typedef struct xfs_agi { __be32 agi_root; /* root of inode btree */ __be32 agi_level; /* levels in inode btree */ __be32 agi_freecount; /* number of free inodes */ + __be32 agi_newino; /* new inode just allocated */ __be32 agi_dirino; /* last directory inode chunk */ /* @@ -139,6 +160,13 @@ typedef struct xfs_agi { * still being referenced. */ __be32 agi_unlinked[XFS_AGI_UNLINKED_BUCKETS]; + + uuid_t agi_uuid; /* uuid of filesystem */ + __be32 agi_crc; /* crc of agi sector */ + __be32 agi_pad32; + __be64 agi_lsn; /* last write sequence */ + + /* structure must be padded to 64 bit alignment */ } xfs_agi_t; #define XFS_AGI_MAGICNUM 0x00000001 @@ -171,11 +199,31 @@ extern const struct xfs_buf_ops xfs_agi_buf_ops; */ #define XFS_AGFL_DADDR(mp) ((xfs_daddr_t)(3 << (mp)->m_sectbb_log)) #define XFS_AGFL_BLOCK(mp) XFS_HDR_BLOCK(mp, XFS_AGFL_DADDR(mp)) -#define XFS_AGFL_SIZE(mp) ((mp)->m_sb.sb_sectsize / sizeof(xfs_agblock_t)) #define XFS_BUF_TO_AGFL(bp) ((xfs_agfl_t *)((bp)->b_addr)) +#define XFS_BUF_TO_AGFL_BNO(mp, bp) \ + (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \ + &(XFS_BUF_TO_AGFL(bp)->agfl_bno[0]) : \ + (__be32 *)(bp)->b_addr) + +/* + * Size of the AGFL. For CRC-enabled filesystes we steal a couple of + * slots in the beginning of the block for a proper header with the + * location information and CRC. + */ +#define XFS_AGFL_SIZE(mp) \ + (((mp)->m_sb.sb_sectsize - \ + (xfs_sb_version_hascrc(&((mp)->m_sb)) ? \ + sizeof(struct xfs_agfl) : 0)) / \ + sizeof(xfs_agblock_t)) + typedef struct xfs_agfl { - __be32 agfl_bno[1]; /* actually XFS_AGFL_SIZE(mp) */ + __be32 agfl_magicnum; + __be32 agfl_seqno; + uuid_t agfl_uuid; + __be64 agfl_lsn; + __be32 agfl_crc; + __be32 agfl_bno[]; /* actually XFS_AGFL_SIZE(mp) */ } xfs_agfl_t; /* diff --git a/include/xfs_buf_item.h b/include/xfs_buf_item.h index 101ef83..c256606 100644 --- a/include/xfs_buf_item.h +++ b/include/xfs_buf_item.h @@ -45,12 +45,18 @@ extern kmem_zone_t *xfs_buf_item_zone; * once the changes have been replayed into the buffer. */ #define XFS_BLF_BTREE_BUF (1<<5) +#define XFS_BLF_AGF_BUF (1<<6) +#define XFS_BLF_AGFL_BUF (1<<7) +#define XFS_BLF_AGI_BUF (1<<8) #define XFS_BLF_TYPE_MASK \ (XFS_BLF_UDQUOT_BUF | \ XFS_BLF_PDQUOT_BUF | \ XFS_BLF_GDQUOT_BUF | \ - XFS_BLF_BTREE_BUF) + XFS_BLF_BTREE_BUF | \ + XFS_BLF_AGF_BUF | \ + XFS_BLF_AGFL_BUF | \ + XFS_BLF_AGI_BUF) #define XFS_BLF_CHUNK 128 #define XFS_BLF_SHIFT 7 diff --git a/libxfs/xfs_alloc.c b/libxfs/xfs_alloc.c index 61cdc6c..d8f3566 100644 --- a/libxfs/xfs_alloc.c +++ b/libxfs/xfs_alloc.c @@ -410,53 +410,84 @@ xfs_alloc_fixup_trees( return 0; } -static void +static bool xfs_agfl_verify( struct xfs_buf *bp) { -#ifdef WHEN_CRCS_COME_ALONG - /* - * we cannot actually do any verification of the AGFL because mkfs does - * not initialise the AGFL to zero or NULL. Hence the only valid part of - * the AGFL is what the AGF says is active. We can't get to the AGF, so - * we can't verify just those entries are valid. - * - * This problem goes away when the CRC format change comes along as that - * requires the AGFL to be initialised by mkfs. At that point, we can - * verify the blocks in the agfl -active or not- lie within the bounds - * of the AG. Until then, just leave this check ifdef'd out. - */ struct xfs_mount *mp = bp->b_target->bt_mount; struct xfs_agfl *agfl = XFS_BUF_TO_AGFL(bp); - int agfl_ok = 1; - int i; + if (!uuid_equal(&agfl->agfl_uuid, &mp->m_sb.sb_uuid)) + return false; + if (be32_to_cpu(agfl->agfl_magicnum) != XFS_AGFL_MAGIC) + return false; + /* + * during growfs operations, the perag is not fully initialised, + * so we can't use it for any useful checking. growfs ensures we can't + * use it by using uncached buffers that don't have the perag attached + * so we can detect and avoid this problem. + */ + if (bp->b_pag && be32_to_cpu(agfl->agfl_seqno) != bp->b_pag->pag_agno) + return false; + for (i = 0; i < XFS_AGFL_SIZE(mp); i++) { - if (be32_to_cpu(agfl->agfl_bno[i]) == NULLAGBLOCK || + if (be32_to_cpu(agfl->agfl_bno[i]) != NULLAGBLOCK && be32_to_cpu(agfl->agfl_bno[i]) >= mp->m_sb.sb_agblocks) - agfl_ok = 0; + return false; } + return true; +} + +static void +xfs_agfl_read_verify( + struct xfs_buf *bp) +{ + struct xfs_mount *mp = bp->b_target->bt_mount; + int agfl_ok = 1; + + /* + * There is no verification of non-crc AGFLs because mkfs does not + * initialise the AGFL to zero or NULL. Hence the only valid part of the + * AGFL is what the AGF says is active. We can't get to the AGF, so we + * can't verify just those entries are valid. + */ + if (!xfs_sb_version_hascrc(&mp->m_sb)) + return; + + agfl_ok = xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agfl, agfl_crc)); + + agfl_ok = agfl_ok && xfs_agfl_verify(bp); if (!agfl_ok) { - XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, agfl); + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); xfs_buf_ioerror(bp, EFSCORRUPTED); } -#endif } static void xfs_agfl_write_verify( struct xfs_buf *bp) { - xfs_agfl_verify(bp); -} + struct xfs_mount *mp = bp->b_target->bt_mount; + struct xfs_buf_log_item *bip = bp->b_fspriv; -static void -xfs_agfl_read_verify( - struct xfs_buf *bp) -{ - xfs_agfl_verify(bp); + /* no verification of non-crc AGFLs */ + if (!xfs_sb_version_hascrc(&mp->m_sb)) + return; + + if (!xfs_agfl_verify(bp)) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); + xfs_buf_ioerror(bp, EFSCORRUPTED); + return; + } + + if (bip) + XFS_BUF_TO_AGFL(bp)->agfl_lsn = cpu_to_be64(bip->bli_item.li_lsn); + + xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agfl, agfl_crc)); } const struct xfs_buf_ops xfs_agfl_buf_ops = { @@ -1964,18 +1995,18 @@ xfs_alloc_get_freelist( int btreeblk) /* destination is a AGF btree */ { xfs_agf_t *agf; /* a.g. freespace structure */ - xfs_agfl_t *agfl; /* a.g. freelist structure */ xfs_buf_t *agflbp;/* buffer for a.g. freelist structure */ xfs_agblock_t bno; /* block number returned */ + __be32 *agfl_bno; int error; int logflags; - xfs_mount_t *mp; /* mount structure */ + xfs_mount_t *mp = tp->t_mountp; xfs_perag_t *pag; /* per allocation group data */ - agf = XFS_BUF_TO_AGF(agbp); /* * Freelist is empty, give up. */ + agf = XFS_BUF_TO_AGF(agbp); if (!agf->agf_flcount) { *bnop = NULLAGBLOCK; return 0; @@ -1983,15 +2014,17 @@ xfs_alloc_get_freelist( /* * Read the array of free blocks. */ - mp = tp->t_mountp; - if ((error = xfs_alloc_read_agfl(mp, tp, - be32_to_cpu(agf->agf_seqno), &agflbp))) + error = xfs_alloc_read_agfl(mp, tp, be32_to_cpu(agf->agf_seqno), + &agflbp); + if (error) return error; - agfl = XFS_BUF_TO_AGFL(agflbp); + + /* * Get the block number and update the data structures. */ - bno = be32_to_cpu(agfl->agfl_bno[be32_to_cpu(agf->agf_flfirst)]); + agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp); + bno = be32_to_cpu(agfl_bno[be32_to_cpu(agf->agf_flfirst)]); be32_add_cpu(&agf->agf_flfirst, 1); xfs_trans_brelse(tp, agflbp); if (be32_to_cpu(agf->agf_flfirst) == XFS_AGFL_SIZE(mp)) @@ -2040,11 +2073,14 @@ xfs_alloc_log_agf( offsetof(xfs_agf_t, agf_freeblks), offsetof(xfs_agf_t, agf_longest), offsetof(xfs_agf_t, agf_btreeblks), + offsetof(xfs_agf_t, agf_uuid), sizeof(xfs_agf_t) }; trace_xfs_agf(tp->t_mountp, XFS_BUF_TO_AGF(bp), fields, _RET_IP_); + xfs_trans_buf_set_type(tp, bp, XFS_BLF_AGF_BUF); + xfs_btree_offsets(fields, offsets, XFS_AGF_NUM_BITS, &first, &last); xfs_trans_log_buf(tp, bp, (uint)first, (uint)last); } @@ -2081,12 +2117,13 @@ xfs_alloc_put_freelist( int btreeblk) /* block came from a AGF btree */ { xfs_agf_t *agf; /* a.g. freespace structure */ - xfs_agfl_t *agfl; /* a.g. free block array */ __be32 *blockp;/* pointer to array entry */ int error; int logflags; xfs_mount_t *mp; /* mount structure */ xfs_perag_t *pag; /* per allocation group data */ + __be32 *agfl_bno; + int startoff; agf = XFS_BUF_TO_AGF(agbp); mp = tp->t_mountp; @@ -2094,7 +2131,6 @@ xfs_alloc_put_freelist( if (!agflbp && (error = xfs_alloc_read_agfl(mp, tp, be32_to_cpu(agf->agf_seqno), &agflbp))) return error; - agfl = XFS_BUF_TO_AGFL(agflbp); be32_add_cpu(&agf->agf_fllast, 1); if (be32_to_cpu(agf->agf_fllast) == XFS_AGFL_SIZE(mp)) agf->agf_fllast = 0; @@ -2115,32 +2151,38 @@ xfs_alloc_put_freelist( xfs_alloc_log_agf(tp, agbp, logflags); ASSERT(be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp)); - blockp = &agfl->agfl_bno[be32_to_cpu(agf->agf_fllast)]; + + agfl_bno = XFS_BUF_TO_AGFL_BNO(mp, agflbp); + blockp = &agfl_bno[be32_to_cpu(agf->agf_fllast)]; *blockp = cpu_to_be32(bno); + startoff = (char *)blockp - (char *)agflbp->b_addr; + xfs_alloc_log_agf(tp, agbp, logflags); - xfs_trans_log_buf(tp, agflbp, - (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl), - (int)((xfs_caddr_t)blockp - (xfs_caddr_t)agfl + - sizeof(xfs_agblock_t) - 1)); + + xfs_trans_buf_set_type(tp, agflbp, XFS_BLF_AGFL_BUF); + xfs_trans_log_buf(tp, agflbp, startoff, + startoff + sizeof(xfs_agblock_t) - 1); return 0; } -static void +static bool xfs_agf_verify( + struct xfs_mount *mp, struct xfs_buf *bp) { - struct xfs_mount *mp = bp->b_target->bt_mount; - struct xfs_agf *agf; - int agf_ok; + struct xfs_agf *agf = XFS_BUF_TO_AGF(bp); - agf = XFS_BUF_TO_AGF(bp); + if (xfs_sb_version_hascrc(&mp->m_sb) && + !uuid_equal(&agf->agf_uuid, &mp->m_sb.sb_uuid)) + return false; - agf_ok = agf->agf_magicnum == cpu_to_be32(XFS_AGF_MAGIC) && - XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) && - be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) && - be32_to_cpu(agf->agf_flfirst) < XFS_AGFL_SIZE(mp) && - be32_to_cpu(agf->agf_fllast) < XFS_AGFL_SIZE(mp) && - be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp); + if (!(agf->agf_magicnum == cpu_to_be32(XFS_AGF_MAGIC) && + XFS_AGF_GOOD_VERSION(be32_to_cpu(agf->agf_versionnum)) && + be32_to_cpu(agf->agf_freeblks) <= be32_to_cpu(agf->agf_length) && + be32_to_cpu(agf->agf_flfirst) < XFS_AGFL_SIZE(mp) && + be32_to_cpu(agf->agf_fllast) < XFS_AGFL_SIZE(mp) && + be32_to_cpu(agf->agf_flcount) <= XFS_AGFL_SIZE(mp))) + return false; /* * during growfs operations, the perag is not fully initialised, @@ -2148,33 +2190,58 @@ xfs_agf_verify( * use it by using uncached buffers that don't have the perag attached * so we can detect and avoid this problem. */ - if (bp->b_pag) - agf_ok = agf_ok && be32_to_cpu(agf->agf_seqno) == - bp->b_pag->pag_agno; + if (bp->b_pag && be32_to_cpu(agf->agf_seqno) != bp->b_pag->pag_agno) + return false; - if (xfs_sb_version_haslazysbcount(&mp->m_sb)) - agf_ok = agf_ok && be32_to_cpu(agf->agf_btreeblks) <= - be32_to_cpu(agf->agf_length); + if (xfs_sb_version_haslazysbcount(&mp->m_sb) && + be32_to_cpu(agf->agf_btreeblks) > be32_to_cpu(agf->agf_length)) + return false; + + return true;; - if (unlikely(XFS_TEST_ERROR(!agf_ok, mp, XFS_ERRTAG_ALLOC_READ_AGF, - XFS_RANDOM_ALLOC_READ_AGF))) { - XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, agf); - xfs_buf_ioerror(bp, EFSCORRUPTED); - } } static void xfs_agf_read_verify( struct xfs_buf *bp) { - xfs_agf_verify(bp); + struct xfs_mount *mp = bp->b_target->bt_mount; + int agf_ok = 1; + + if (xfs_sb_version_hascrc(&mp->m_sb)) + agf_ok = xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agf, agf_crc)); + + agf_ok = agf_ok && xfs_agf_verify(mp, bp); + + if (unlikely(XFS_TEST_ERROR(!agf_ok, mp, XFS_ERRTAG_ALLOC_READ_AGF, + XFS_RANDOM_ALLOC_READ_AGF))) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); + xfs_buf_ioerror(bp, EFSCORRUPTED); + } } static void xfs_agf_write_verify( struct xfs_buf *bp) { - xfs_agf_verify(bp); + struct xfs_mount *mp = bp->b_target->bt_mount; + struct xfs_buf_log_item *bip = bp->b_fspriv; + + if (!xfs_agf_verify(mp, bp)) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); + xfs_buf_ioerror(bp, EFSCORRUPTED); + return; + } + + if (!xfs_sb_version_hascrc(&mp->m_sb)) + return; + + if (bip) + XFS_BUF_TO_AGF(bp)->agf_lsn = cpu_to_be64(bip->bli_item.li_lsn); + + xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agf, agf_crc)); } const struct xfs_buf_ops xfs_agf_buf_ops = { diff --git a/libxfs/xfs_ialloc.c b/libxfs/xfs_ialloc.c index 529d92d..88dc02a 100644 --- a/libxfs/xfs_ialloc.c +++ b/libxfs/xfs_ialloc.c @@ -1263,6 +1263,7 @@ xfs_ialloc_log_agi( /* * Log the allocation group inode header buffer. */ + xfs_trans_buf_set_type(tp, bp, XFS_BLF_AGI_BUF); xfs_trans_log_buf(tp, bp, first, last); } @@ -1280,19 +1281,23 @@ xfs_check_agi_unlinked( #define xfs_check_agi_unlinked(agi) #endif -static void +static bool xfs_agi_verify( struct xfs_buf *bp) { struct xfs_mount *mp = bp->b_target->bt_mount; struct xfs_agi *agi = XFS_BUF_TO_AGI(bp); - int agi_ok; + if (xfs_sb_version_hascrc(&mp->m_sb) && + !uuid_equal(&agi->agi_uuid, &mp->m_sb.sb_uuid)) + return false; /* * Validate the magic number of the agi block. */ - agi_ok = agi->agi_magicnum == cpu_to_be32(XFS_AGI_MAGIC) && - XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum)); + if (agi->agi_magicnum != cpu_to_be32(XFS_AGI_MAGIC)) + return false; + if (!XFS_AGI_GOOD_VERSION(be32_to_cpu(agi->agi_versionnum))) + return false; /* * during growfs operations, the perag is not fully initialised, @@ -1300,30 +1305,52 @@ xfs_agi_verify( * use it by using uncached buffers that don't have the perag attached * so we can detect and avoid this problem. */ - if (bp->b_pag) - agi_ok = agi_ok && be32_to_cpu(agi->agi_seqno) == - bp->b_pag->pag_agno; + if (bp->b_pag && be32_to_cpu(agi->agi_seqno) != bp->b_pag->pag_agno) + return false; - if (unlikely(XFS_TEST_ERROR(!agi_ok, mp, XFS_ERRTAG_IALLOC_READ_AGI, - XFS_RANDOM_IALLOC_READ_AGI))) { - XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, agi); - xfs_buf_ioerror(bp, EFSCORRUPTED); - } xfs_check_agi_unlinked(agi); + return true; } static void xfs_agi_read_verify( struct xfs_buf *bp) { - xfs_agi_verify(bp); + struct xfs_mount *mp = bp->b_target->bt_mount; + int agi_ok = 1; + + if (xfs_sb_version_hascrc(&mp->m_sb)) + agi_ok = xfs_verify_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agi, agi_crc)); + agi_ok = agi_ok && xfs_agi_verify(bp); + + if (unlikely(XFS_TEST_ERROR(!agi_ok, mp, XFS_ERRTAG_IALLOC_READ_AGI, + XFS_RANDOM_IALLOC_READ_AGI))) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); + xfs_buf_ioerror(bp, EFSCORRUPTED); + } } static void xfs_agi_write_verify( struct xfs_buf *bp) { - xfs_agi_verify(bp); + struct xfs_mount *mp = bp->b_target->bt_mount; + struct xfs_buf_log_item *bip = bp->b_fspriv; + + if (!xfs_agi_verify(bp)) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, bp->b_addr); + xfs_buf_ioerror(bp, EFSCORRUPTED); + return; + } + + if (!xfs_sb_version_hascrc(&mp->m_sb)) + return; + + if (bip) + XFS_BUF_TO_AGI(bp)->agi_lsn = cpu_to_be64(bip->bli_item.li_lsn); + xfs_update_cksum(bp->b_addr, BBTOB(bp->b_length), + offsetof(struct xfs_agi, agi_crc)); } const struct xfs_buf_ops xfs_agi_buf_ops = { -- 1.7.10 _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs