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2020-07-16ovl: relax WARN_ON() when decoding lower directory file handleAmir Goldstein1-1/+1
Decoding a lower directory file handle to overlay path with cold inode/dentry cache may go as follows: 1. Decode real lower file handle to lower dir path 2. Check if lower dir is indexed (was copied up) 3. If indexed, get the upper dir path from index 4. Lookup upper dir path in overlay 5. If overlay path found, verify that overlay lower is the lower dir from step 1 On failure to verify step 5 above, user will get an ESTALE error and a WARN_ON will be printed. A mismatch in step 5 could be a result of lower directory that was renamed while overlay was offline, after that lower directory has been copied up and indexed. This is a scripted reproducer based on xfstest overlay/052: # Create lower subdir create_dirs create_test_files $lower/lowertestdir/subdir mount_dirs # Copy up lower dir and encode lower subdir file handle touch $SCRATCH_MNT/lowertestdir test_file_handles $SCRATCH_MNT/lowertestdir/subdir -p -o $tmp.fhandle # Rename lower dir offline unmount_dirs mv $lower/lowertestdir $lower/lowertestdir.new/ mount_dirs # Attempt to decode lower subdir file handle test_file_handles $SCRATCH_MNT -p -i $tmp.fhandle Since this WARN_ON() can be triggered by user we need to relax it. Fixes: 4b91c30a5a19 ("ovl: lookup connected ancestor of dir in inode cache") Cc: <stable@vger.kernel.org> # v4.16+ Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-06-04ovl: add accessor for ofs->upper_mntMiklos Szeredi1-3/+3
Next patch will remove ofs->upper_mnt, so add an accessor function for this field. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-05-13ovl: return required buffer size for file handlesLubos Dolezel1-10/+8
Overlayfs doesn't work well with the fanotify mechanism. Fanotify first probes for the required buffer size for the file handle, but overlayfs currently bails out without passing the size back. That results in errors in the kernel log, such as: [527944.485384] overlayfs: failed to encode file handle (/, err=-75, buflen=0, len=29, type=1) [527944.485386] fanotify: failed to encode fid (fsid=ae521e68.a434d95f, type=255, bytes=0, err=-2) Signed-off-by: Lubos Dolezel <lubos@dolezel.info> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-05-13ovl: potential crash in ovl_fid_to_fh()Dan Carpenter1-0/+3
The "buflen" value comes from the user and there is a potential that it could be zero. In do_handle_to_path() we know that "handle->handle_bytes" is non-zero and we do: handle_dwords = handle->handle_bytes >> 2; So values 1-3 become zero. Then in ovl_fh_to_dentry() we do: int len = fh_len << 2; So now len is in the "0,4-128" range and a multiple of 4. But if "buflen" is zero it will try to copy negative bytes when we do the memcpy in ovl_fid_to_fh(). memcpy(&fh->fb, fid, buflen - OVL_FH_WIRE_OFFSET); And that will lead to a crash. Thanks to Amir Goldstein for his help with this patch. Fixes: cbe7fba8edfc ("ovl: make sure that real fid is 32bit aligned in memory") Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Cc: <stable@vger.kernel.org> # v5.5 Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-03-17ovl: ovl_obtain_alias(): don't call d_instantiate_anon() for oldAl Viro1-17/+21
The situation is the same as for __d_obtain_alias() (which is what that thing is parallel to) - if we find a preexisting alias, we want to grab it, drop the inode and return the alias we'd found. The only thing d_instantiate_anon() does compared to that is spurious security_d_instiate() that has already been done to that dentry with exact same arguments. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-03-17ovl: decide if revalidate needed on a per-dentry basisMiklos Szeredi1-0/+2
Allow completely skipping ->revalidate() on a per-dentry basis, in case the underlying layers used for a dentry do not themselves have ->revalidate(). E.g. negative overlay dentry has no underlying layers, hence revalidate is unnecessary. Or if lower layer is remote but overlay dentry is pure-upper, then can skip revalidate. The following places need to update whether the dentry needs revalidate or not: - fill-super (root dentry) - lookup - create - fh_to_dentry Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-24ovl: layer is constMiklos Szeredi1-6/+6
The ovl_layer struct is never modified except at initialization. Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-22ovl: generalize the lower_layers[] arrayAmir Goldstein1-4/+2
Rename lower_layers[] array to layers[], extend its size by one and initialize layers[0] with upper layer values. Lower layers are now addressed with index 1..numlower. layers[0] is reserved even with lower only overlay. [SzM: replace ofs->numlower with ofs->numlayer, the latter's value is incremented by one] Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2020-01-22ovl: use pr_fmt auto generate prefixlijiazi1-6/+6
Use pr_fmt auto generate "overlayfs: " prefix. Signed-off-by: lijiazi <lijiazi@xiaomi.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-12-10ovl: make sure that real fid is 32bit aligned in memoryAmir Goldstein1-31/+49
Seprate on-disk encoding from in-memory and on-wire resresentation of overlay file handle. In-memory and on-wire we only ever pass around pointers to struct ovl_fh, which encapsulates at offset 3 the on-disk format struct ovl_fb. struct ovl_fb encapsulates at offset 21 the real file handle. That makes sure that the real file handle is always 32bit aligned in-memory when passed down to the underlying filesystem. On-disk format remains the same and store/load are done into correctly aligned buffer. New nfs exported file handles are exported with aligned real fid. Old nfs file handles are copied to an aligned buffer before being decoded. Reported-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-09-11ovl: Fix dereferencing possible ERR_PTR()Ding Xiang1-2/+1
if ovl_encode_real_fh() fails, no memory was allocated and the error in the error-valued pointer should be returned. Fixes: 9b6faee07470 ("ovl: check ERR_PTR() return value from ovl_encode_fh()") Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com> Cc: <stable@vger.kernel.org> # v4.16+ Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2019-06-19treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500Thomas Gleixner1-4/+1
Based on 2 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation this program is free software you can redistribute it and or modify it under the terms of the gnu general public license version 2 as published by the free software foundation # extracted by the scancode license scanner the SPDX license identifier GPL-2.0-only has been chosen to replace the boilerplate/reference in 4122 file(s). Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Enrico Weigelt <info@metux.net> Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Allison Randal <allison@lohutok.net> Cc: linux-spdx@vger.kernel.org Link: https://lkml.kernel.org/r/20190604081206.933168790@linutronix.de Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2019-04-26ovl_lookup_real_one(): don't bother with strlen()Al Viro1-1/+1
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2018-11-21ovl: fix decode of dir file handle with multi lower layersAmir Goldstein1-3/+3
When decoding a lower file handle, we first call ovl_check_origin_fh() with connected=false to get any real lower dentry for overlay inode cache lookup. If the real dentry is a disconnected dir dentry, ovl_check_origin_fh() is called again with connected=true to get a connected real dentry and find the lower layer the real dentry belongs to. If the first call returned a connected real dentry, we use it to lookup an overlay connected dentry, but the first ovl_check_origin_fh() call with connected=false did not check that the found dentry is under the root of the layer (see ovl_acceptable()), it only checked that the found dentry super block matches the uuid of the lower file handle. In case there are multiple lower layers on the same fs and the found dentry is not from the top most lower layer, using the layer index returned from the first ovl_check_origin_fh() is wrong and we end up failing to decode the file handle. Fix this by always calling ovl_check_origin_fh() with connected=true if we got a directory dentry in the first call. Fixes: 8b58924ad55c ("ovl: lookup in inode cache first when decoding...") Cc: <stable@vger.kernel.org> # v4.17 Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-07-20ovl: Modify ovl_lookup() and friends to lookup metacopy dentryVivek Goyal1-0/+3
This patch modifies ovl_lookup() and friends to lookup metacopy dentries. It also allows for presence of metacopy dentries in lower layer. During lookup, check for presence of OVL_XATTR_METACOPY and if not present, set OVL_UPPERDATA bit in flags. We don't support metacopy feature with nfs_export. So in nfs_export code, we set OVL_UPPERDATA flag set unconditionally if upper inode exists. Do not follow metacopy origin if we find a metacopy only inode and metacopy feature is not enabled for that mount. Like redirect, this can have security implications where an attacker could hand craft upper and try to gain access to file on lower which it should not have to begin with. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Reviewed-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-05-31ovl: Pass argument to ovl_get_inode() in a structureVivek Goyal1-1/+7
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 <vgoyal@redhat.com> Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-04-12ovl: consistent i_ino for non-samefs with xinoAmir Goldstein1-1/+1
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 <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-04-12ovl: cleanup setting OVL_INDEXVivek Goyal1-3/+0
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-04-12ovl: lookup in inode cache first when decoding lower file handleAmir Goldstein1-25/+33
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 <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-04-12ovl: do not try to reconnect a disconnected origin dentryAmir Goldstein1-2/+2
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 <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-04-12ovl: disambiguate ovl_encode_fh()Amir Goldstein1-6/+6
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 <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-02-26ovl: fix ptr_ret.cocci warningsFengguang Wu1-1/+1
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 <amir73il@gmail.com> Signed-off-by: Fengguang Wu <fengguang.wu@intel.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-02-16ovl: check ERR_PTR() return value from ovl_lookup_real()Amir Goldstein1-2/+2
Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Fixes: 061701540349 ("ovl: lookup indexed ancestor of lower dir") Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-02-16ovl: check lower ancestry on encode of lower dir file handleAmir Goldstein1-44/+166
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 <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-02-05ovl: check ERR_PTR() return value from ovl_encode_fh()Amir Goldstein1-0/+3
Another fix for an issue reported by 0-day robot. Reported-by: Dan Carpenter <dan.carpenter@oracle.com> Fixes: 8ed5eec9d6c4 ("ovl: encode pure upper file handles") Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: lookup indexed ancestor of lower dirAmir Goldstein1-1/+40
ovl_lookup_real() in lower layer walks back lower parents to find the topmost indexed parent. If an indexed ancestor is found before reaching lower layer root, ovl_lookup_real() is called recursively with upper layer to walk back from indexed upper to the topmost connected/hashed upper parent (or up to root). ovl_lookup_real() in upper layer then walks forward to connect the topmost upper overlay dir dentry and ovl_lookup_real() in lower layer continues to walk forward to connect the decoded lower overlay dir dentry. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: lookup connected ancestor of dir in inode cacheAmir Goldstein1-6/+93
Decoding a dir file handle requires walking backward up to layer root and for lower dir also checking the index to see if any of the parents have been copied up. Lookup overlay ancestor dentry in inode/dentry cache by decoded real parents to shortcut looking up all the way back to layer root. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode pure lower dir file handlesAmir Goldstein1-17/+26
Similar to decoding a pure upper dir file handle, decoding a pure lower dir file handle is implemented by looking an overlay dentry of the same path as the pure lower path and verifying that the overlay dentry's real lower matches the decoded real lower file handle. Unlike the case of upper dir file handle, the lookup of overlay path by lower real path can fail or find a mismatched overlay dentry if any of the lower parents have been copied up and renamed. To address this case we will need to check if any of the lower parents are indexed. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode indexed dir file handlesAmir Goldstein1-0/+13
Decoding an indexed dir file handle is done by looking up the file handle in index dir by name and then decoding the upper dir from the index origin file handle. The decoded upper path is used to lookup an overlay dentry of the same path. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode lower file handles of unlinked but open filesAmir Goldstein1-2/+21
Lookup overlay inode in cache by origin inode, so we can decode a file handle of an open file even if the index has a whiteout index entry to mark this overlay inode was unlinked. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode indexed non-dir file handlesAmir Goldstein1-25/+46
Decoding an indexed non-dir file handle is similar to decoding a lower non-dir file handle, but additionally, we lookup the file handle in index dir by name to find the real upper inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode lower non-dir file handlesAmir Goldstein1-11/+42
Decoding a lower non-dir file handle is done by decoding the lower dentry from underlying lower fs, finding or allocating an overlay inode that is hashed by the real lower inode and instantiating an overlay dentry with that inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: encode lower file handlesAmir Goldstein1-8/+2
For indexed or lower non-dir, encode a non-connectable lower file handle from origin inode. For indexed or lower dir, when ofs->numlower == 1, encode a lower file handle from lower dir. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: copy up before encoding non-connectable dir file handleAmir Goldstein1-4/+49
Decoding a merge dir, whose origin's parent is under a redirected lower dir is not always possible. As a simple aproximation, we do not encode lower dir file handles when overlay has multiple lower layers and origin is below the topmost lower layer. We should later relax this condition and copy up only the parent that is under a redirected lower. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: encode non-indexed upper file handlesAmir Goldstein1-5/+35
We only need to encode origin if there is a chance that the same object was encoded pre copy up and then we need to stay consistent with the same encoding also after copy up. In case a non-pure upper is not indexed, then it was copied up before NFS export support was enabled. In that case, we don't need to worry about staying consistent with pre copy up encoding and we encode an upper file handle. This mitigates the problem that with no index, we cannot find an upper inode from origin inode, so we cannot decode a non-indexed upper from origin file handle. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode connected upper dir file handlesAmir Goldstein1-1/+230
Until this change, we decoded upper file handles by instantiating an overlay dentry from the real upper dentry. This is sufficient to handle pure upper files, but insufficient to handle merge/impure dirs. To that end, if decoded real upper dir is connected and hashed, we lookup an overlay dentry with the same path as the real upper dir. If decoded real upper is non-dir, we instantiate a disconnected overlay dentry as before this change. Because ovl_fh_to_dentry() returns a connected overlay dir dentry, exportfs never needs to call get_parent() and get_name() to reconnect an upper overlay dir. Because connectable non-dir file handles are not supported, exportfs will not be able to use fh_to_parent() and get_name() methods to reconnect a disconnected non-dir to its parent. Therefore, the methods get_parent() and get_name() are implemented just to print out a sanity warning and the method fh_to_parent() is implemented to warn the user that using the 'subtree_check' exportfs option is not supported. An alternative approach could have been to implement instantiating of an overlay directory inode from origin/index and implement get_parent() and get_name() by calling into underlying fs operations and them instantiating the overlay parent dir. The reasons for not choosing the get_parent() approach were: - Obtaining a disconnected overlay dir dentry would requires a delicate re-factoring of ovl_lookup() to get a dentry with overlay parent info. It was preferred to avoid doing that re-factoring unless it was proven worthy. - Going down the path of disconnected dir would mean that the (non trivial) code path of d_splice_alias() could be traveled and that meant writing more tests and introduces race cases that are very hard to hit on purpose. Taking the path of connecting overlay dentry by forward lookup is therefore the safe and boring way to avoid surprises. The culprits of the chosen "connected overlay dentry" approach: - We need to take special care to rename of ancestors while connecting the overlay dentry by real dentry path. These subtleties are usually handled by generic exportfs and VFS code. - In a hypothetical workload, we could end up in a loop trying to connect, interrupted by rename and restarting connect forever. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: decode pure upper file handlesAmir Goldstein1-0/+97
Decoding an upper file handle is done by decoding the upper dentry from underlying upper fs, finding or allocating an overlay inode that is hashed by the real upper inode and instantiating an overlay dentry with that inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
2018-01-24ovl: encode pure upper file handlesAmir Goldstein1-0/+98
Encode overlay file handles as struct ovl_fh containing the file handle encoding of the real upper inode. Signed-off-by: Amir Goldstein <amir73il@gmail.com> Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>