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xfs: growfs: use uncached buffers for new headers
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When writing the new AG headers to disk, we can't attach write
verifiers because they have a dependency on the struct xfs-perag
being attached to the buffer to be fully initialised and growfs
can't fully initialise them until later in the process.

The simplest way to avoid this problem is to use uncached buffers
for writing the new headers. These buffers don't have the xfs-perag
attached to them, so it's simple to detect in the write verifier and
be able to skip the checks that need the xfs-perag.

This enables us to attach the appropriate buffer ops to the buffer
and hence calculate CRCs on the way to disk. IT also means that the
buffer is torn down immediately, and so the first access to the AG
headers will re-read the header from disk and perform full
verification of the buffer. This way we also can catch corruptions
due to problems that went undetected in growfs.

Signed-off-by: Dave Chinner <[email protected]>
Reviewed-by Rich Johnston <[email protected]>
Signed-off-by: Ben Myers <[email protected]>
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Dave Chinner authored and Ben Myers committed Nov 13, 2012
1 parent b64f3a3 commit fd23683
Showing 1 changed file with 41 additions and 22 deletions.
63 changes: 41 additions & 22 deletions fs/xfs/xfs_fsops.c
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Original file line number Diff line number Diff line change
Expand Up @@ -114,6 +114,26 @@ xfs_fs_geometry(
return 0;
}

static struct xfs_buf *
xfs_growfs_get_hdr_buf(
struct xfs_mount *mp,
xfs_daddr_t blkno,
size_t numblks,
int flags)
{
struct xfs_buf *bp;

bp = xfs_buf_get_uncached(mp->m_ddev_targp, numblks, flags);
if (!bp)
return NULL;

xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
bp->b_bn = blkno;
bp->b_maps[0].bm_bn = blkno;

return bp;
}

static int
xfs_growfs_data_private(
xfs_mount_t *mp, /* mount point for filesystem */
Expand Down Expand Up @@ -189,15 +209,15 @@ xfs_growfs_data_private(
/*
* AG freelist header block
*/
bp = xfs_buf_get(mp->m_ddev_targp,
XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
XFS_FSS_TO_BB(mp, 1), 0);
bp = xfs_growfs_get_hdr_buf(mp,
XFS_AG_DADDR(mp, agno, XFS_AGF_DADDR(mp)),
XFS_FSS_TO_BB(mp, 1), 0);
if (!bp) {
error = ENOMEM;
goto error0;
}

agf = XFS_BUF_TO_AGF(bp);
memset(agf, 0, mp->m_sb.sb_sectsize);
agf->agf_magicnum = cpu_to_be32(XFS_AGF_MAGIC);
agf->agf_versionnum = cpu_to_be32(XFS_AGF_VERSION);
agf->agf_seqno = cpu_to_be32(agno);
Expand Down Expand Up @@ -226,15 +246,15 @@ xfs_growfs_data_private(
/*
* AG inode header block
*/
bp = xfs_buf_get(mp->m_ddev_targp,
XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
XFS_FSS_TO_BB(mp, 1), 0);
bp = xfs_growfs_get_hdr_buf(mp,
XFS_AG_DADDR(mp, agno, XFS_AGI_DADDR(mp)),
XFS_FSS_TO_BB(mp, 1), 0);
if (!bp) {
error = ENOMEM;
goto error0;
}

agi = XFS_BUF_TO_AGI(bp);
memset(agi, 0, mp->m_sb.sb_sectsize);
agi->agi_magicnum = cpu_to_be32(XFS_AGI_MAGIC);
agi->agi_versionnum = cpu_to_be32(XFS_AGI_VERSION);
agi->agi_seqno = cpu_to_be32(agno);
Expand All @@ -255,16 +275,16 @@ xfs_growfs_data_private(
/*
* BNO btree root block
*/
bp = xfs_buf_get(mp->m_ddev_targp,
XFS_AGB_TO_DADDR(mp, agno, XFS_BNO_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);
bp = xfs_growfs_get_hdr_buf(mp,
XFS_AGB_TO_DADDR(mp, agno, XFS_BNO_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);

if (!bp) {
error = ENOMEM;
goto error0;
}
xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
xfs_btree_init_block(mp, bp, XFS_ABTB_MAGIC, 0, 1, 0);

xfs_btree_init_block(mp, bp, XFS_ABTB_MAGIC, 0, 1, 0);
arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
arec->ar_blockcount = cpu_to_be32(
Expand All @@ -278,16 +298,15 @@ xfs_growfs_data_private(
/*
* CNT btree root block
*/
bp = xfs_buf_get(mp->m_ddev_targp,
XFS_AGB_TO_DADDR(mp, agno, XFS_CNT_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);
bp = xfs_growfs_get_hdr_buf(mp,
XFS_AGB_TO_DADDR(mp, agno, XFS_CNT_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);
if (!bp) {
error = ENOMEM;
goto error0;
}
xfs_buf_zero(bp, 0, BBTOB(bp->b_length));
xfs_btree_init_block(mp, bp, XFS_ABTC_MAGIC, 0, 1, 0);

xfs_btree_init_block(mp, bp, XFS_ABTC_MAGIC, 0, 1, 0);
arec = XFS_ALLOC_REC_ADDR(mp, XFS_BUF_TO_BLOCK(bp), 1);
arec->ar_startblock = cpu_to_be32(XFS_PREALLOC_BLOCKS(mp));
arec->ar_blockcount = cpu_to_be32(
Expand All @@ -302,14 +321,14 @@ xfs_growfs_data_private(
/*
* INO btree root block
*/
bp = xfs_buf_get(mp->m_ddev_targp,
XFS_AGB_TO_DADDR(mp, agno, XFS_IBT_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);
bp = xfs_growfs_get_hdr_buf(mp,
XFS_AGB_TO_DADDR(mp, agno, XFS_IBT_BLOCK(mp)),
BTOBB(mp->m_sb.sb_blocksize), 0);
if (!bp) {
error = ENOMEM;
goto error0;
}
xfs_buf_zero(bp, 0, BBTOB(bp->b_length));

xfs_btree_init_block(mp, bp, XFS_IBT_MAGIC, 0, 0, 0);

error = xfs_bwrite(bp);
Expand Down

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