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Fix lseek(SEEK_DATA/SEEK_HOLE) mmap consistency

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When using lseek(2) to report data/holes memory mapped regions of
the file were ignored.  This could result in incorrect results.
To handle this zfs_holey_common() was updated to asynchronously
writeback any dirty mmap(2) regions prior to reporting holes.

Additionally, while not strictly required, the dn_struct_rwlock is
now held over the dirty check to prevent the dnode structure from
changing.  This ensures that a clean dnode can't be dirtied before
the data/hole is located.  The range lock is now also taken to
ensure the call cannot race with zfs_write().

Furthermore, the code was refactored to provide a dnode_is_dirty()
helper function which checks the dnode for any dirty records to
determine its dirtiness.

Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Reviewed-by: Rich Ercolani <rincebrain@gmail.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #11900
Closes #12724
This commit is contained in:
Brian Behlendorf
2021-11-07 13:27:44 -08:00
committed by GitHub
parent 4b87c1981d
commit de198f2d95
18 changed files with 305 additions and 32 deletions
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include/sys/dnode.h
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@@ -425,6 +425,7 @@ boolean_t dnode_add_ref(dnode_t *dn, void *ref);
void dnode_rele(dnode_t *dn, void *ref);
void dnode_rele_and_unlock(dnode_t *dn, void *tag, boolean_t evicting);
int dnode_try_claim(objset_t *os, uint64_t object, int slots);
boolean_t dnode_is_dirty(dnode_t *dn);
void dnode_setdirty(dnode_t *dn, dmu_tx_t *tx);
void dnode_set_dirtyctx(dnode_t *dn, dmu_tx_t *tx, void *tag);
void dnode_sync(dnode_t *dn, dmu_tx_t *tx);