linux.git/fs/overlayfs/export.c, branch v4.18

ovl: Pass argument to ovl_get_inode() in a structure

2018-05-31T09:06:12+00:00

ovl_get_inode() right now has 5 parameters. Soon this patch series will
add 2 more and suddenly argument list starts looking too long.

Hence pass arguments to ovl_get_inode() in a structure and it looks
little cleaner.

Signed-off-by: Vivek Goyal 
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: consistent i_ino for non-samefs with xino

2018-04-12T10:04:50+00:00

When overlay layers are not all on the same fs, but all inode numbers
of underlying fs do not use the high 'xino' bits, overlay st_ino values
are constant and persistent.

In that case, set i_ino value to the same value as st_ino for nfsd
readdirplus validator.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: cleanup setting OVL_INDEX

2018-04-12T10:04:49+00:00

Signed-off-by: Miklos Szeredi

ovl: lookup in inode cache first when decoding lower file handle

2018-04-12T10:04:49+00:00

When decoding a lower file handle, we need to check if lower file was
copied up and indexed and if it has a whiteout index, we need to check
if this is an unlinked but open non-dir before returning -ESTALE.

To find out if this is an unlinked but open non-dir we need to lookup
an overlay inode in inode cache by lower inode and that requires decoding
the lower file handle before looking in inode cache.

Before this change, if the lower inode turned out to be a directory, we
may have paid an expensive cost to reconnect that lower directory for
nothing.

After this change, we start by decoding a disconnected lower dentry and
using the lower inode for looking up an overlay inode in inode cache.
If we find overlay inode and dentry in cache, we avoid the index lookup
overhead. If we don't find an overlay inode and dentry in cache, then we
only need to decode a connected lower dentry in case the lower dentry is
a non-indexed directory.

The xfstests group overlay/exportfs tests decoding overlayfs file
handles after drop_caches with different states of the file at encode
and decode time. Overall the tests in the group call ovl_lower_fh_to_d()
89 times to decode a lower file handle.

Before this change, the tests called ovl_get_index_fh() 75 times and
reconnect_one() 61 times.
After this change, the tests call ovl_get_index_fh() 70 times and
reconnect_one() 59 times. The 2 cases where reconnect_one() was avoided
are cases where a non-upper directory file handle was encoded, then the
directory removed and then file handle was decoded.

To demonstrate the affect on decoding file handles with hot inode/dentry
cache, the drop_caches call in the tests was disabled. Without
drop_caches, there are no reconnect_one() calls at all before or after
the change. Before the change, there are 75 calls to ovl_get_index_fh(),
exactly as the case with drop_caches. After the change, there are only
10 calls to ovl_get_index_fh().

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: do not try to reconnect a disconnected origin dentry

2018-04-12T10:04:49+00:00

On lookup of non directory, we try to decode the origin file handle
stored in upper inode. The origin file handle is supposed to be decoded
to a disconnected non-dir dentry, which is fine, because we only need
the lower inode of a copy up origin.

However, if the origin file handle somehow turns out to be a directory
we pay the expensive cost of reconnecting the directory dentry, only to
get a mismatch file type and drop the dentry.

Optimize this case by explicitly opting out of reconnecting the dentry.
Opting-out of reconnect is done by passing a NULL acceptable callback
to exportfs_decode_fh().

While the case described above is a strange corner case that does not
really need to be optimized, the API added for this optimization will
be used by a following patch to optimize a more common case of decoding
an overlayfs file handle.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: disambiguate ovl_encode_fh()

2018-04-12T10:04:49+00:00

Rename ovl_encode_fh() to ovl_encode_real_fh() to differentiate from the
exportfs function ovl_encode_inode_fh() and change the latter to
ovl_encode_fh() to match the exportfs method name.

Rename ovl_decode_fh() to ovl_decode_real_fh() for consistency.

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: fix ptr_ret.cocci warnings

2018-02-26T11:45:20+00:00

fs/overlayfs/export.c:459:10-16: WARNING: PTR_ERR_OR_ZERO can be used

 Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR

Generated by: scripts/coccinelle/api/ptr_ret.cocci

Fixes: 4b91c30a5a19 ("ovl: lookup connected ancestor of dir in inode cache")
CC: Amir Goldstein 
Signed-off-by: Fengguang Wu 
Signed-off-by: Miklos Szeredi

ovl: check ERR_PTR() return value from ovl_lookup_real()

2018-02-16T14:53:20+00:00

Reported-by: Dan Carpenter 
Fixes: 061701540349 ("ovl: lookup indexed ancestor of lower dir")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: check lower ancestry on encode of lower dir file handle

2018-02-16T14:53:20+00:00

This change relaxes copy up on encode of merge dir with lower layer > 1
and handles the case of encoding a merge dir with lower layer 1, where an
ancestor is a non-indexed merge dir. In that case, decode of the lower
file handle will not have been possible if the non-indexed ancestor is
redirected before or after encode.

Before encoding a non-upper directory file handle from real layer N, we
need to check if it will be possible to reconnect an overlay dentry from
the real lower decoded dentry. This is done by following the overlay
ancestry up to a "layer N connected" ancestor and verifying that all
parents along the way are "layer N connectable". If an ancestor that is
NOT "layer N connectable" is found, we need to copy up an ancestor, which
is "layer N connectable", thus making that ancestor "layer N connected".
For example:

 layer 1: /a
 layer 2: /a/b/c

The overlay dentry /a is NOT "layer 2 connectable", because if dir /a is
copied up and renamed, upper dir /a will be indexed by lower dir /a from
layer 1. The dir /a from layer 2 will never be indexed, so the algorithm
in ovl_lookup_real_ancestor() (*) will not be able to lookup a connected
overlay dentry from the connected lower dentry /a/b/c.

To avoid this problem on decode time, we need to copy up an ancestor of
/a/b/c, which is "layer 2 connectable", on encode time. That ancestor is
/a/b. After copy up (and index) of /a/b, it will become "layer 2 connected"
and when the time comes to decode the file handle from lower dentry /a/b/c,
ovl_lookup_real_ancestor() will find the indexed ancestor /a/b and decoding
a connected overlay dentry will be accomplished.

(*) the algorithm in ovl_lookup_real_ancestor() can be improved to lookup
an entry /a in the lower layers above layer N and find the indexed dir /a
from layer 1. If that improvement is made, then the check for "layer N
connected" will need to verify there are no redirects in lower layers above
layer N. In the example above, /a will be "layer 2 connectable". However,
if layer 2 dir /a is a target of a layer 1 redirect, then /a will NOT be
"layer 2 connectable":

 layer 1: /A (redirect = /a)
 layer 2: /a/b/c

Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi

ovl: check ERR_PTR() return value from ovl_encode_fh()

2018-02-05T08:50:29+00:00

Another fix for an issue reported by 0-day robot.

Reported-by: Dan Carpenter 
Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles")
Signed-off-by: Amir Goldstein 
Signed-off-by: Miklos Szeredi