diff options
Diffstat (limited to 'fs/xfs/libxfs/xfs_inode_util.c')
| -rw-r--r-- | fs/xfs/libxfs/xfs_inode_util.c | 282 |
1 files changed, 282 insertions, 0 deletions
diff --git a/fs/xfs/libxfs/xfs_inode_util.c b/fs/xfs/libxfs/xfs_inode_util.c index 8654cb3d79ef..5739871ac370 100644 --- a/fs/xfs/libxfs/xfs_inode_util.c +++ b/fs/xfs/libxfs/xfs_inode_util.c @@ -18,6 +18,10 @@ #include "xfs_ialloc.h" #include "xfs_health.h" #include "xfs_bmap.h" +#include "xfs_error.h" +#include "xfs_trace.h" +#include "xfs_ag.h" +#include "xfs_iunlink_item.h" uint16_t xfs_flags2diflags( @@ -344,3 +348,281 @@ xfs_inode_init( xfs_trans_log_inode(tp, ip, flags); } + +/* + * In-Core Unlinked List Lookups + * ============================= + * + * Every inode is supposed to be reachable from some other piece of metadata + * with the exception of the root directory. Inodes with a connection to a + * file descriptor but not linked from anywhere in the on-disk directory tree + * are collectively known as unlinked inodes, though the filesystem itself + * maintains links to these inodes so that on-disk metadata are consistent. + * + * XFS implements a per-AG on-disk hash table of unlinked inodes. The AGI + * header contains a number of buckets that point to an inode, and each inode + * record has a pointer to the next inode in the hash chain. This + * singly-linked list causes scaling problems in the iunlink remove function + * because we must walk that list to find the inode that points to the inode + * being removed from the unlinked hash bucket list. + * + * Hence we keep an in-memory double linked list to link each inode on an + * unlinked list. Because there are 64 unlinked lists per AGI, keeping pointer + * based lists would require having 64 list heads in the perag, one for each + * list. This is expensive in terms of memory (think millions of AGs) and cache + * misses on lookups. Instead, use the fact that inodes on the unlinked list + * must be referenced at the VFS level to keep them on the list and hence we + * have an existence guarantee for inodes on the unlinked list. + * + * Given we have an existence guarantee, we can use lockless inode cache lookups + * to resolve aginos to xfs inodes. This means we only need 8 bytes per inode + * for the double linked unlinked list, and we don't need any extra locking to + * keep the list safe as all manipulations are done under the AGI buffer lock. + * Keeping the list up to date does not require memory allocation, just finding + * the XFS inode and updating the next/prev unlinked list aginos. + */ + +/* + * Update the prev pointer of the next agino. Returns -ENOLINK if the inode + * is not in cache. + */ +static int +xfs_iunlink_update_backref( + struct xfs_perag *pag, + xfs_agino_t prev_agino, + xfs_agino_t next_agino) +{ + struct xfs_inode *ip; + + /* No update necessary if we are at the end of the list. */ + if (next_agino == NULLAGINO) + return 0; + + ip = xfs_iunlink_lookup(pag, next_agino); + if (!ip) + return -ENOLINK; + + ip->i_prev_unlinked = prev_agino; + return 0; +} + +/* + * Point the AGI unlinked bucket at an inode and log the results. The caller + * is responsible for validating the old value. + */ +STATIC int +xfs_iunlink_update_bucket( + struct xfs_trans *tp, + struct xfs_perag *pag, + struct xfs_buf *agibp, + unsigned int bucket_index, + xfs_agino_t new_agino) +{ + struct xfs_agi *agi = agibp->b_addr; + xfs_agino_t old_value; + int offset; + + ASSERT(xfs_verify_agino_or_null(pag, new_agino)); + + old_value = be32_to_cpu(agi->agi_unlinked[bucket_index]); + trace_xfs_iunlink_update_bucket(tp->t_mountp, pag->pag_agno, bucket_index, + old_value, new_agino); + + /* + * We should never find the head of the list already set to the value + * passed in because either we're adding or removing ourselves from the + * head of the list. + */ + if (old_value == new_agino) { + xfs_buf_mark_corrupt(agibp); + xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI); + return -EFSCORRUPTED; + } + + agi->agi_unlinked[bucket_index] = cpu_to_be32(new_agino); + offset = offsetof(struct xfs_agi, agi_unlinked) + + (sizeof(xfs_agino_t) * bucket_index); + xfs_trans_log_buf(tp, agibp, offset, offset + sizeof(xfs_agino_t) - 1); + return 0; +} + +static int +xfs_iunlink_insert_inode( + struct xfs_trans *tp, + struct xfs_perag *pag, + struct xfs_buf *agibp, + struct xfs_inode *ip) +{ + struct xfs_mount *mp = tp->t_mountp; + struct xfs_agi *agi = agibp->b_addr; + xfs_agino_t next_agino; + xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino); + short bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS; + int error; + + /* + * Get the index into the agi hash table for the list this inode will + * go on. Make sure the pointer isn't garbage and that this inode + * isn't already on the list. + */ + next_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]); + if (next_agino == agino || + !xfs_verify_agino_or_null(pag, next_agino)) { + xfs_buf_mark_corrupt(agibp); + xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI); + return -EFSCORRUPTED; + } + + /* + * Update the prev pointer in the next inode to point back to this + * inode. + */ + error = xfs_iunlink_update_backref(pag, agino, next_agino); + if (error == -ENOLINK) + error = xfs_iunlink_reload_next(tp, agibp, agino, next_agino); + if (error) + return error; + + if (next_agino != NULLAGINO) { + /* + * There is already another inode in the bucket, so point this + * inode to the current head of the list. + */ + error = xfs_iunlink_log_inode(tp, ip, pag, next_agino); + if (error) + return error; + ip->i_next_unlinked = next_agino; + } + + /* Point the head of the list to point to this inode. */ + ip->i_prev_unlinked = NULLAGINO; + return xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index, agino); +} + +/* + * This is called when the inode's link count has gone to 0 or we are creating + * a tmpfile via O_TMPFILE. The inode @ip must have nlink == 0. + * + * We place the on-disk inode on a list in the AGI. It will be pulled from this + * list when the inode is freed. + */ +int +xfs_iunlink( + struct xfs_trans *tp, + struct xfs_inode *ip) +{ + struct xfs_mount *mp = tp->t_mountp; + struct xfs_perag *pag; + struct xfs_buf *agibp; + int error; + + ASSERT(VFS_I(ip)->i_nlink == 0); + ASSERT(VFS_I(ip)->i_mode != 0); + trace_xfs_iunlink(ip); + + pag = xfs_perag_get(mp, XFS_INO_TO_AGNO(mp, ip->i_ino)); + + /* Get the agi buffer first. It ensures lock ordering on the list. */ + error = xfs_read_agi(pag, tp, 0, &agibp); + if (error) + goto out; + + error = xfs_iunlink_insert_inode(tp, pag, agibp, ip); +out: + xfs_perag_put(pag); + return error; +} + +static int +xfs_iunlink_remove_inode( + struct xfs_trans *tp, + struct xfs_perag *pag, + struct xfs_buf *agibp, + struct xfs_inode *ip) +{ + struct xfs_mount *mp = tp->t_mountp; + struct xfs_agi *agi = agibp->b_addr; + xfs_agino_t agino = XFS_INO_TO_AGINO(mp, ip->i_ino); + xfs_agino_t head_agino; + short bucket_index = agino % XFS_AGI_UNLINKED_BUCKETS; + int error; + + trace_xfs_iunlink_remove(ip); + + /* + * Get the index into the agi hash table for the list this inode will + * go on. Make sure the head pointer isn't garbage. + */ + head_agino = be32_to_cpu(agi->agi_unlinked[bucket_index]); + if (!xfs_verify_agino(pag, head_agino)) { + XFS_CORRUPTION_ERROR(__func__, XFS_ERRLEVEL_LOW, mp, + agi, sizeof(*agi)); + xfs_ag_mark_sick(pag, XFS_SICK_AG_AGI); + return -EFSCORRUPTED; + } + + /* + * Set our inode's next_unlinked pointer to NULL and then return + * the old pointer value so that we can update whatever was previous + * to us in the list to point to whatever was next in the list. + */ + error = xfs_iunlink_log_inode(tp, ip, pag, NULLAGINO); + if (error) + return error; + + /* + * Update the prev pointer in the next inode to point back to previous + * inode in the chain. + */ + error = xfs_iunlink_update_backref(pag, ip->i_prev_unlinked, + ip->i_next_unlinked); + if (error == -ENOLINK) + error = xfs_iunlink_reload_next(tp, agibp, ip->i_prev_unlinked, + ip->i_next_unlinked); + if (error) + return error; + + if (head_agino != agino) { + struct xfs_inode *prev_ip; + + prev_ip = xfs_iunlink_lookup(pag, ip->i_prev_unlinked); + if (!prev_ip) { + xfs_inode_mark_sick(ip, XFS_SICK_INO_CORE); + return -EFSCORRUPTED; + } + + error = xfs_iunlink_log_inode(tp, prev_ip, pag, + ip->i_next_unlinked); + prev_ip->i_next_unlinked = ip->i_next_unlinked; + } else { + /* Point the head of the list to the next unlinked inode. */ + error = xfs_iunlink_update_bucket(tp, pag, agibp, bucket_index, + ip->i_next_unlinked); + } + + ip->i_next_unlinked = NULLAGINO; + ip->i_prev_unlinked = 0; + return error; +} + +/* + * Pull the on-disk inode from the AGI unlinked list. + */ +int +xfs_iunlink_remove( + struct xfs_trans *tp, + struct xfs_perag *pag, + struct xfs_inode *ip) +{ + struct xfs_buf *agibp; + int error; + + trace_xfs_iunlink_remove(ip); + + /* Get the agi buffer first. It ensures lock ordering on the list. */ + error = xfs_read_agi(pag, tp, 0, &agibp); + if (error) + return error; + + return xfs_iunlink_remove_inode(tp, pag, agibp, ip); +} |