On Wed, Jun 19, 2024 at 09:05:29AM +0800, Zizhi Wo wrote: > > > 在 2024/6/19 8:22, Darrick J. Wong 写道: > > On Tue, Jun 18, 2024 at 09:32:08PM +0800, Zizhi Wo wrote: > > > A concurrent file creation and little writing could unexpectedly return > > > -ENOSPC error since there is a race window that the allocator could get > > > the wrong agf->agf_longest. > > > > > > Write file process steps: > > > 1) Find the entry that best meets the conditions, then calculate the start > > > address and length of the remaining part of the entry after allocation. > > > 2) Delete this entry and update the agf->agf_longest. > > > 3) Insert the remaining unused parts of this entry based on the > > > calculations in 1), and update the agf->agf_longest again if necessary. > > > > > > Create file process steps: > > > 1) Check whether there are free inodes in the inode chunk. > > > 2) If there is no free inode, check whether there has space for creating > > > inode chunks, perform the no-lock judgment first. > > > 3) If the judgment succeeds, the judgment is performed again with agf lock > > > held. Otherwire, an error is returned directly. > > > > > > If the write process is in step 2) but not go to 3) yet, the create file > > > process goes to 2) at this time, it will be mistaken for no space, > > > resulting in the file system still has space but the file creation fails. > > > > > > We have sent two different commits to the community in order to fix this > > > problem[1][2]. Unfortunately, both solutions have flaws. In [2], I > > > discussed with Dave and Darrick, realized that a better solution to this > > > problem requires the "last cnt record tracking" to be ripped out of the > > > generic btree code. And surprisingly, Dave directly provided his fix code. > > > This patch includes appropriate modifications based on his tmp-code to > > > address this issue. > > > > > > The entire fix can be roughly divided into two parts: > > > 1) Delete the code related to lastrec-update in the generic btree code. > > > 2) Place the process of updating longest freespace with cntbt separately > > > to the end of the cntbt modifications. And only these two scenarios > > > need to be considered: > > > 2.1) In the deletion scenario, directly update the longest to the > > > rightmost record of the cntbt. > > > 2.2) In the insertion scenario, determine whether the cntbt has the > > > record that larger than the previous longest. > > > > > > [1] https://lore.kernel.org/all/20240419061848.1032366-2-yebin10@xxxxxxxxxx > > > [2] https://lore.kernel.org/all/20240604071121.3981686-1-wozizhi@xxxxxxxxxx > > > > > > Reported by: Ye Bin <yebin10@xxxxxxxxxx> > > > Signed-off-by: Zizhi Wo <wozizhi@xxxxxxxxxx> > > > --- > > > fs/xfs/libxfs/xfs_alloc.c | 116 ++++++++++++++++++++++++++++++++ > > > fs/xfs/libxfs/xfs_alloc_btree.c | 64 ------------------ > > > fs/xfs/libxfs/xfs_btree.c | 51 -------------- > > > fs/xfs/libxfs/xfs_btree.h | 16 ++--- > > > 4 files changed, 120 insertions(+), 127 deletions(-) > > > > > > diff --git a/fs/xfs/libxfs/xfs_alloc.c b/fs/xfs/libxfs/xfs_alloc.c > > > index 6c55a6e88eba..74e40f75a278 100644 > > > --- a/fs/xfs/libxfs/xfs_alloc.c > > > +++ b/fs/xfs/libxfs/xfs_alloc.c > > > @@ -465,6 +465,99 @@ xfs_alloc_fix_len( > > > args->len = rlen; > > > } > > > +/* > > > + * Determine if the cursor points to the block that contains the right-most > > > + * block of records in the by-count btree. This block contains the largest > > > + * contiguous free extent in the AG, so if we modify ia record in this block we > > > > a record > > > > > + * need to call xfs_alloc_fixup_longest() once the modifications are done to > > > + * ensure the agf->agf_longest field is kept up to date with the longest free > > > + * extent tracked by the by-count btree. > > > + */ > > > +static bool > > > +xfs_alloc_cursor_at_lastrec( > > > + struct xfs_btree_cur *cnt_cur) > > > +{ > > > + struct xfs_btree_block *block; > > > + union xfs_btree_ptr ptr; > > > + struct xfs_buf *bp; > > > + > > > + block = xfs_btree_get_block(cnt_cur, 0, &bp); > > > + > > > + xfs_btree_get_sibling(cnt_cur, block, &ptr, XFS_BB_RIGHTSIB); > > > + if (!xfs_btree_ptr_is_null(cnt_cur, &ptr)) > > > + return false; > > > + return true; > > > +} > > > + > > > +/* > > > + * Update the longest contiguous free extent in the AG from the by-count cursor > > > + * that is passed to us. This should be done at the end of any allocation or > > > + * freeing operation that touches the longest extent in the btree. > > > + * > > > + * Needing to update the longest extent can be determined by calling > > > + * xfs_alloc_cursor_at_lastrec() after the cursor is positioned for record > > > + * modification but before the modification begins. > > > + */ > > > +static int > > > +xfs_alloc_fixup_longest( > > > + struct xfs_btree_cur *cnt_cur, > > > + int reason) > > > +{ > > > + struct xfs_perag *pag = cnt_cur->bc_ag.pag; > > > + struct xfs_agf *agf; > > > + struct xfs_buf *bp; > > > + struct xfs_btree_block *block; > > > + int error; > > > + int i; > > > + int numrecs; > > > + > > > + /* > > > + * Lookup last rec and update AGF. > > > + * > > > + * In case of LASTREC_DELREC, after called xfs_alloc_lookup_ge(), the > > > + * ptr is in the rightmost edge, and we need to update the last record > > > + * of this block as the longest free extent. > > > + * > > > + * In case of LASTREC_INSREC, because only one new record is inserted > > > + * each time, only need to check whether the cntbt has a record that > > > + * larger than the previous longest. Note that we can't update the > > > + * longest with xfs_alloc_get_rec() as the xfs_verify_agbno() may not > > > + * pass because pag->block_count is updated on the outside. > > > + */ > > > + error = xfs_alloc_lookup_ge(cnt_cur, 0, pag->pagf_longest + 1, &i); > > > + if (error) > > > + return error; > > > + > > > + if (i == 1 || reason == LASTREC_DELREC) { > > > + if (XFS_IS_CORRUPT(pag->pag_mount, > > > + i == 1 && reason == LASTREC_DELREC)) { > > > + xfs_btree_mark_sick(cnt_cur); > > > + return -EFSCORRUPTED; > > > + } > > > + > > > + block = xfs_btree_get_block(cnt_cur, 0, &bp); > > > + numrecs = xfs_btree_get_numrecs(block); > > > + > > > + if (numrecs) { > > > + xfs_alloc_rec_t *rrp; > > > + > > > + rrp = XFS_ALLOC_REC_ADDR(cnt_cur->bc_mp, block, > > > + numrecs); > > > + pag->pagf_longest = be32_to_cpu(rrp->ar_blockcount); > > > + } else { > > > + /* empty tree */ > > > + pag->pagf_longest = 0; > > > + } > > > + } > > > > Hum. Would it work if we did: > > > > xfs_extlen_t len; > > > > xfs_alloc_lookup_le(cnt_cur, 0, mp->m_sb.sb_agsize, &i); > > > > if (i) > > xfs_alloc_get_rec(cnt_cur, ..., &len, &i); > > if (!i) > > len = 0; > > > > pag->pagf_longest = len; > > > > This performs a LE lookup on the longest possible free extent (aka the > > AG size). If we get pointed at a record, that's the longest free extent > > and we can set pag->pagf_longest to that. If we get no record, then > > there's zero space and we can zero it. > > > > I checked it out, and it doesn't seem to work that way, for two reasons: > 1) In the insertion scenario, if the longest extent is continuous with > the extent to be inserted, the system deletes the longest extent first, > and then inserts a more longer extent. So in the last update, we should > not look at le, but ge. > 2) For the deletion scenario, because the start block is 0, the extent > value found is not the next longest extent value, but probably a very > small extent value (for example, its start block is very small), which > will also cause us to update incorrectly. > > So in summary, I think it is appropriate to use ge here. Ah, right, you're correct. LE could work if you were willing to do: xfs_alloc_lookup_le(cnt_cur, mp->m_sb.sb_agsize, mp->m_sb.sb_agsize, &i); But you might as well stick with the GE lookup. > On the other > hand, xfs_alloc_get_rec() introduces problems. As I wrote in the > comment, an internal call to xfs_verify_agbno() may fail because the > longest extent added, it could be greater than pag->block_count as > pag->block_count is later than the longest update. Oh, because xfs_ag_extend_space (aka growfs) calls xfs_free_extent before updating pag->block_count. But still, please don't use XFS_ALLOC_REC_ADDR when you already have a btree cursor handy. union xfs_btree_rec *rec; xfs_alloc_lookup_ge(cnt_cur, 0, mp->m_sb.sb_agsize, &i); if (i) xfs_btree_get_rec(cur, &rec, &i); if (i) { struct xfs_alloc_rec_incore irec; /* * pagf->block_count updates lag cntbt updates, so * open-code the btree record access */ xfs_alloc_btrec_to_irec(rec, &irec); pagf->pagf_longest = irec.ar_blockcount; } else { /* empty tree */ pagf->pagf_longest = 0; } --D > > Then I think you don't need the @reason argument either. > > Mm-hm, the reasons for this will be removed from the comment and stated > next time in the commit message. > > Thanks > Zizhi Wo > > > > > --D > > > > > > + > > > + bp = cnt_cur->bc_ag.agbp; > > > + agf = bp->b_addr; > > > + agf->agf_longest = cpu_to_be32(pag->pagf_longest); > > > + xfs_alloc_log_agf(cnt_cur->bc_tp, bp, XFS_AGF_LONGEST); > > > + > > > + return 0; > > > +} > > > + > > > /* > > > * Update the two btrees, logically removing from freespace the extent > > > * starting at rbno, rlen blocks. The extent is contained within the > > > @@ -489,6 +582,7 @@ xfs_alloc_fixup_trees( > > > xfs_extlen_t nflen1=0; /* first new free length */ > > > xfs_extlen_t nflen2=0; /* second new free length */ > > > struct xfs_mount *mp; > > > + bool fixup_longest = false; > > > mp = cnt_cur->bc_mp; > > > @@ -577,6 +671,10 @@ xfs_alloc_fixup_trees( > > > nfbno2 = rbno + rlen; > > > nflen2 = (fbno + flen) - nfbno2; > > > } > > > + > > > + if (xfs_alloc_cursor_at_lastrec(cnt_cur)) > > > + fixup_longest = true; > > > + > > > /* > > > * Delete the entry from the by-size btree. > > > */ > > > @@ -654,6 +752,10 @@ xfs_alloc_fixup_trees( > > > return -EFSCORRUPTED; > > > } > > > } > > > + > > > + if (fixup_longest) > > > + return xfs_alloc_fixup_longest(cnt_cur, LASTREC_DELREC); > > > + > > > return 0; > > > } > > > @@ -1956,6 +2058,7 @@ xfs_free_ag_extent( > > > int i; > > > int error; > > > struct xfs_perag *pag = agbp->b_pag; > > > + bool fixup_longest = false; > > > bno_cur = cnt_cur = NULL; > > > mp = tp->t_mountp; > > > @@ -2219,8 +2322,13 @@ xfs_free_ag_extent( > > > } > > > xfs_btree_del_cursor(bno_cur, XFS_BTREE_NOERROR); > > > bno_cur = NULL; > > > + > > > /* > > > * In all cases we need to insert the new freespace in the by-size tree. > > > + * > > > + * If this new freespace is being inserted in the block that contains > > > + * the largest free space in the btree, make sure we also fix up the > > > + * agf->agf-longest tracker field. > > > */ > > > if ((error = xfs_alloc_lookup_eq(cnt_cur, nbno, nlen, &i))) > > > goto error0; > > > @@ -2229,6 +2337,8 @@ xfs_free_ag_extent( > > > error = -EFSCORRUPTED; > > > goto error0; > > > } > > > + if (xfs_alloc_cursor_at_lastrec(cnt_cur)) > > > + fixup_longest = true; > > > if ((error = xfs_btree_insert(cnt_cur, &i))) > > > goto error0; > > > if (XFS_IS_CORRUPT(mp, i != 1)) { > > > @@ -2236,6 +2346,12 @@ xfs_free_ag_extent( > > > error = -EFSCORRUPTED; > > > goto error0; > > > } > > > + if (fixup_longest) { > > > + error = xfs_alloc_fixup_longest(cnt_cur, LASTREC_INSREC); > > > + if (error) > > > + goto error0; > > > + } > > > + > > > xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR); > > > cnt_cur = NULL; > > > diff --git a/fs/xfs/libxfs/xfs_alloc_btree.c b/fs/xfs/libxfs/xfs_alloc_btree.c > > > index 6ef5ddd89600..585e98e87ef9 100644 > > > --- a/fs/xfs/libxfs/xfs_alloc_btree.c > > > +++ b/fs/xfs/libxfs/xfs_alloc_btree.c > > > @@ -115,67 +115,6 @@ xfs_allocbt_free_block( > > > return 0; > > > } > > > -/* > > > - * Update the longest extent in the AGF > > > - */ > > > -STATIC void > > > -xfs_allocbt_update_lastrec( > > > - struct xfs_btree_cur *cur, > > > - const struct xfs_btree_block *block, > > > - const union xfs_btree_rec *rec, > > > - int ptr, > > > - int reason) > > > -{ > > > - struct xfs_agf *agf = cur->bc_ag.agbp->b_addr; > > > - struct xfs_perag *pag; > > > - __be32 len; > > > - int numrecs; > > > - > > > - ASSERT(!xfs_btree_is_bno(cur->bc_ops)); > > > - > > > - switch (reason) { > > > - case LASTREC_UPDATE: > > > - /* > > > - * If this is the last leaf block and it's the last record, > > > - * then update the size of the longest extent in the AG. > > > - */ > > > - if (ptr != xfs_btree_get_numrecs(block)) > > > - return; > > > - len = rec->alloc.ar_blockcount; > > > - break; > > > - case LASTREC_INSREC: > > > - if (be32_to_cpu(rec->alloc.ar_blockcount) <= > > > - be32_to_cpu(agf->agf_longest)) > > > - return; > > > - len = rec->alloc.ar_blockcount; > > > - break; > > > - case LASTREC_DELREC: > > > - numrecs = xfs_btree_get_numrecs(block); > > > - if (ptr <= numrecs) > > > - return; > > > - ASSERT(ptr == numrecs + 1); > > > - > > > - if (numrecs) { > > > - xfs_alloc_rec_t *rrp; > > > - > > > - rrp = XFS_ALLOC_REC_ADDR(cur->bc_mp, block, numrecs); > > > - len = rrp->ar_blockcount; > > > - } else { > > > - len = 0; > > > - } > > > - > > > - break; > > > - default: > > > - ASSERT(0); > > > - return; > > > - } > > > - > > > - agf->agf_longest = len; > > > - pag = cur->bc_ag.agbp->b_pag; > > > - pag->pagf_longest = be32_to_cpu(len); > > > - xfs_alloc_log_agf(cur->bc_tp, cur->bc_ag.agbp, XFS_AGF_LONGEST); > > > -} > > > - > > > STATIC int > > > xfs_allocbt_get_minrecs( > > > struct xfs_btree_cur *cur, > > > @@ -493,7 +432,6 @@ const struct xfs_btree_ops xfs_bnobt_ops = { > > > .set_root = xfs_allocbt_set_root, > > > .alloc_block = xfs_allocbt_alloc_block, > > > .free_block = xfs_allocbt_free_block, > > > - .update_lastrec = xfs_allocbt_update_lastrec, > > > .get_minrecs = xfs_allocbt_get_minrecs, > > > .get_maxrecs = xfs_allocbt_get_maxrecs, > > > .init_key_from_rec = xfs_allocbt_init_key_from_rec, > > > @@ -511,7 +449,6 @@ const struct xfs_btree_ops xfs_bnobt_ops = { > > > const struct xfs_btree_ops xfs_cntbt_ops = { > > > .name = "cnt", > > > .type = XFS_BTREE_TYPE_AG, > > > - .geom_flags = XFS_BTGEO_LASTREC_UPDATE, > > > .rec_len = sizeof(xfs_alloc_rec_t), > > > .key_len = sizeof(xfs_alloc_key_t), > > > @@ -525,7 +462,6 @@ const struct xfs_btree_ops xfs_cntbt_ops = { > > > .set_root = xfs_allocbt_set_root, > > > .alloc_block = xfs_allocbt_alloc_block, > > > .free_block = xfs_allocbt_free_block, > > > - .update_lastrec = xfs_allocbt_update_lastrec, > > > .get_minrecs = xfs_allocbt_get_minrecs, > > > .get_maxrecs = xfs_allocbt_get_maxrecs, > > > .init_key_from_rec = xfs_allocbt_init_key_from_rec, > > > diff --git a/fs/xfs/libxfs/xfs_btree.c b/fs/xfs/libxfs/xfs_btree.c > > > index d29547572a68..a5c4af148853 100644 > > > --- a/fs/xfs/libxfs/xfs_btree.c > > > +++ b/fs/xfs/libxfs/xfs_btree.c > > > @@ -1331,30 +1331,6 @@ xfs_btree_init_block_cur( > > > xfs_btree_owner(cur)); > > > } > > > -/* > > > - * Return true if ptr is the last record in the btree and > > > - * we need to track updates to this record. The decision > > > - * will be further refined in the update_lastrec method. > > > - */ > > > -STATIC int > > > -xfs_btree_is_lastrec( > > > - struct xfs_btree_cur *cur, > > > - struct xfs_btree_block *block, > > > - int level) > > > -{ > > > - union xfs_btree_ptr ptr; > > > - > > > - if (level > 0) > > > - return 0; > > > - if (!(cur->bc_ops->geom_flags & XFS_BTGEO_LASTREC_UPDATE)) > > > - return 0; > > > - > > > - xfs_btree_get_sibling(cur, block, &ptr, XFS_BB_RIGHTSIB); > > > - if (!xfs_btree_ptr_is_null(cur, &ptr)) > > > - return 0; > > > - return 1; > > > -} > > > - > > > STATIC void > > > xfs_btree_buf_to_ptr( > > > struct xfs_btree_cur *cur, > > > @@ -2420,15 +2396,6 @@ xfs_btree_update( > > > xfs_btree_copy_recs(cur, rp, rec, 1); > > > xfs_btree_log_recs(cur, bp, ptr, ptr); > > > - /* > > > - * If we are tracking the last record in the tree and > > > - * we are at the far right edge of the tree, update it. > > > - */ > > > - if (xfs_btree_is_lastrec(cur, block, 0)) { > > > - cur->bc_ops->update_lastrec(cur, block, rec, > > > - ptr, LASTREC_UPDATE); > > > - } > > > - > > > /* Pass new key value up to our parent. */ > > > if (xfs_btree_needs_key_update(cur, ptr)) { > > > error = xfs_btree_update_keys(cur, 0); > > > @@ -3617,15 +3584,6 @@ xfs_btree_insrec( > > > goto error0; > > > } > > > - /* > > > - * If we are tracking the last record in the tree and > > > - * we are at the far right edge of the tree, update it. > > > - */ > > > - if (xfs_btree_is_lastrec(cur, block, level)) { > > > - cur->bc_ops->update_lastrec(cur, block, rec, > > > - ptr, LASTREC_INSREC); > > > - } > > > - > > > /* > > > * Return the new block number, if any. > > > * If there is one, give back a record value and a cursor too. > > > @@ -3983,15 +3941,6 @@ xfs_btree_delrec( > > > xfs_btree_set_numrecs(block, --numrecs); > > > xfs_btree_log_block(cur, bp, XFS_BB_NUMRECS); > > > - /* > > > - * If we are tracking the last record in the tree and > > > - * we are at the far right edge of the tree, update it. > > > - */ > > > - if (xfs_btree_is_lastrec(cur, block, level)) { > > > - cur->bc_ops->update_lastrec(cur, block, NULL, > > > - ptr, LASTREC_DELREC); > > > - } > > > - > > > /* > > > * We're at the root level. First, shrink the root block in-memory. > > > * Try to get rid of the next level down. If we can't then there's > > > diff --git a/fs/xfs/libxfs/xfs_btree.h b/fs/xfs/libxfs/xfs_btree.h > > > index f93374278aa1..670470874630 100644 > > > --- a/fs/xfs/libxfs/xfs_btree.h > > > +++ b/fs/xfs/libxfs/xfs_btree.h > > > @@ -154,12 +154,6 @@ struct xfs_btree_ops { > > > int *stat); > > > int (*free_block)(struct xfs_btree_cur *cur, struct xfs_buf *bp); > > > - /* update last record information */ > > > - void (*update_lastrec)(struct xfs_btree_cur *cur, > > > - const struct xfs_btree_block *block, > > > - const union xfs_btree_rec *rec, > > > - int ptr, int reason); > > > - > > > /* records in block/level */ > > > int (*get_minrecs)(struct xfs_btree_cur *cur, int level); > > > int (*get_maxrecs)(struct xfs_btree_cur *cur, int level); > > > @@ -222,15 +216,13 @@ struct xfs_btree_ops { > > > }; > > > /* btree geometry flags */ > > > -#define XFS_BTGEO_LASTREC_UPDATE (1U << 0) /* track last rec externally */ > > > -#define XFS_BTGEO_OVERLAPPING (1U << 1) /* overlapping intervals */ > > > +#define XFS_BTGEO_OVERLAPPING (1U << 0) /* overlapping intervals */ > > > /* > > > - * Reasons for the update_lastrec method to be called. > > > + * Reasons for the xfs_alloc_fixup_longest() to be called. > > > */ > > > -#define LASTREC_UPDATE 0 > > > -#define LASTREC_INSREC 1 > > > -#define LASTREC_DELREC 2 > > > +#define LASTREC_INSREC 0 > > > +#define LASTREC_DELREC 1 > > > union xfs_btree_irec { > > > -- > > > 2.39.2 > > >
