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Fix inode eviction and sync writeback deadlock on Linux #17159

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Fix inode eviction and sync writeback deadlock on Linux #17159

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1 change: 1 addition & 0 deletions include/sys/zfs_znode.h
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Original file line number Diff line number Diff line change
Expand Up @@ -276,6 +276,7 @@ extern int zfs_znode_hold_compare(const void *, const void *);
extern znode_hold_t *zfs_znode_hold_enter(zfsvfs_t *, uint64_t);
extern void zfs_znode_hold_exit(zfsvfs_t *, znode_hold_t *);
extern int zfs_zget(zfsvfs_t *, uint64_t, znode_t **);
extern int zfs_zget_impl(zfsvfs_t *, uint64_t, znode_t **, boolean_t);
extern int zfs_rezget(znode_t *);
extern void zfs_zinactive(znode_t *);
extern void zfs_znode_delete(znode_t *, dmu_tx_t *);
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7 changes: 7 additions & 0 deletions module/os/freebsd/zfs/zfs_znode_os.c
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Expand Up @@ -1081,6 +1081,13 @@ zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
return (err);
}

int
zfs_zget_impl(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp,
boolean_t check_sync)
{
return (zfs_zget(zfsvfs, obj_num, zpp));
}

int
zfs_rezget(znode_t *zp)
{
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22 changes: 20 additions & 2 deletions module/os/linux/zfs/zfs_znode_os.c
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Expand Up @@ -1050,13 +1050,21 @@ zfs_xvattr_set(znode_t *zp, xvattr_t *xvap, dmu_tx_t *tx)

int
zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
{
return (zfs_zget_impl(zfsvfs, obj_num, zpp, B_FALSE));
}

int
zfs_zget_impl(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp,
boolean_t check_sync)
{
dmu_object_info_t doi;
dmu_buf_t *db;
znode_t *zp;
znode_hold_t *zh;
int err;
sa_handle_t *hdl;
boolean_t noloop = B_FALSE;

*zpp = NULL;

Expand Down Expand Up @@ -1115,8 +1123,18 @@ zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
if (igrab(ZTOI(zp)) == NULL) {
if (zp->z_unlinked)
err = SET_ERROR(ENOENT);
else
else {
err = SET_ERROR(EAGAIN);
/*
* In writeback path, I_SYNC flag will be set
* and block inode eviction. So we must not
* loop doing igrab in possible writeback
* path, i.e. zfs_get_data, if inode is being
* evicted and I_SYNC is also set.
*/
if (check_sync && (ZTOI(zp)->i_state & I_SYNC))
noloop = B_TRUE;
}
} else {
*zpp = zp;
err = 0;
Expand All @@ -1126,7 +1144,7 @@ zfs_zget(zfsvfs_t *zfsvfs, uint64_t obj_num, znode_t **zpp)
sa_buf_rele(db, NULL);
zfs_znode_hold_exit(zfsvfs, zh);

if (err == EAGAIN) {
if (err == EAGAIN && !noloop) {
/* inode might need this to finish evict */
cond_resched();
goto again;
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13 changes: 12 additions & 1 deletion module/zfs/zfs_vnops.c
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Expand Up @@ -1342,10 +1342,21 @@ zfs_get_data(void *arg, uint64_t gen, lr_write_t *lr, char *buf,
ASSERT3P(lwb, !=, NULL);
ASSERT3U(size, !=, 0);

error = zfs_zget_impl(zfsvfs, object, &zp, B_TRUE);
#if defined(__linux__)
/*
* Under Linux, EAGAIN indicates the inode is being evicted and I_SYNC
* is also set possibly blocking eviction, so we can't loop in
* zfs_zget to avoid deadlock. Return EIO to force txg sync under such
* scenario.
*/
if (error == EAGAIN)
return (SET_ERROR(EIO));
#endif
/*
* Nothing to do if the file has been removed
*/
if (zfs_zget(zfsvfs, object, &zp) != 0)
if (error)
return (SET_ERROR(ENOENT));
if (zp->z_unlinked) {
/*
Expand Down
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